Private Pilot Oral Exam

• Be at least 17 years old for an airplane rating.
• Read, speak, write, and understand English.
• Hold a U.S. student, sport, or recreational pilot certificate.
• Receive ground training on the § 61.105(b) knowledge areas and an instructor's endorsement certifying you are prepared for the knowledge test.
• Pass the knowledge test.
• Receive flight training in the § 61.107(b) areas of operation, meet the § 61.109 aeronautical experience, and get an instructor's endorsement certifying you are prepared for the practical test.
• Pass the practical test.
• Hold at least a third class medical for the practical test, under § 61.23(a)(3)(iii), unless operating under the § 61.113(i) BasicMed conditions.

The knowledge test result is valid for 24 calendar months, so an applicant who takes it early and trains slowly can watch it expire before the checkride.

40 hours total, of which at least 20 hours dual and 10 hours solo.

Within the dual time:

• 3 hours cross-country.
• 3 hours night, including one cross-country over 100 NM total distance and 10 takeoffs and 10 landings to a full stop in the pattern.
• 3 hours by reference to instruments.
• 3 hours of test preparation within the preceding 2 calendar months of the test.

Within the solo time:

• 5 hours solo cross-country.
• One solo cross-country of 150 NM total with full-stop landings at three points, one leg over 50 NM straight-line.
• 3 takeoffs and landings to a full stop at a towered airport.

Forty hours is the regulatory floor, not a typical total. Most applicants need more.

You may act as PIC of an aircraft you are rated for, carry passengers, and fly for personal or business travel. What you may not do is be paid for it.

• No carrying passengers or property for compensation or hire, and no acting as PIC for compensation or hire, except as § 61.113(b) through (h) provide.
• You may be paid to act as PIC in connection with any business or employment if the flight is only incidental to that business and the aircraft carries no passengers or property for compensation or hire.
• You may not pay less than your pro rata share of the operating expenses, and only fuel, oil, airport expenditures and rental fees are shareable.
• You may tow a glider or an unpowered ultralight if you meet § 61.69.
• An aircraft salesman with 200 hours logged may demonstrate an aircraft to a buyer.
• Charitable and community event flights are allowed under § 91.146. Search and location operations may be reimbursed, but only for fuel, oil, airport expenditures or rental fees, and only where the operation is sanctioned and under the direction and control of a local, State or Federal agency or an organization that conducts search and location operations.

Yes, but only down to your own pro rata share, and only for four categories of expense.

• You may not pay less than your pro rata share of the operating expenses. With one passenger that is half, with three it is a quarter.
• The shareable expenses are fuel, oil, airport expenditures, and rental fees. Nothing else.
• You cannot be reimbursed for your time, and you cannot come out ahead.

The trap is a passenger offering to cover the whole rental. Accepting makes the flight compensation, which a private pilot may not receive.

Two separate definitions and two separate endorsements. An airplane can be one, both, or neither.

• High performance: an engine of more than 200 horsepower.
• Complex: retractable landing gear, flaps, and a controllable pitch propeller. A seaplane needs only flaps and a controllable pitch propeller.

Each requires ground and flight training from an authorized instructor and a one-time logbook endorsement certifying proficiency. Once given, neither expires.

A fixed-gear 182 is high performance but not complex. An Arrow is complex but not high performance. Watch the variant: a 182RG is both.

• The PIC is directly responsible for, and is the final authority as to, the operation of that aircraft.
• In an in-flight emergency requiring immediate action, the PIC may deviate from any rule of part 91 to the extent required to meet that emergency.
• On request of the Administrator, the PIC must send a written report of that deviation.

Deviation authority is not permission to improvise ahead of time. It applies to an emergency already happening, and it is measured against what the emergency actually required.

They answer different questions: who is responsible, and whose logbook it goes in. One flight can have two different answers.

• Acting as PIC means being the person responsible for, and the final authority as to, the operation of the aircraft. One person at a time, and they need the ratings, medical, and currency for that flight.
• Logging PIC is a recordkeeping rule. You may log it as sole manipulator of the controls of an aircraft you are rated in, as the sole occupant, or when acting as PIC of an aircraft requiring more than one pilot.

So on a dual flight a rated pilot logs PIC as sole manipulator while the instructor logs PIC for serving as the authorized instructor, which § 61.51(e)(3) allows whenever the instructor is rated to act as PIC of that aircraft. Both log the time legitimately, and the instructor's entitlement does not depend on being the acting PIC. Who is acting PIC is a separate question: a rated, current and medically qualified pilot receiving instruction can be the one acting.

You must log only what you need to prove something. Everything else is for your own records.

• Required: training and aeronautical experience used to meet the requirements for a certificate, rating, or flight review, and the recent flight experience that keeps you current.
• Optional: everything else. There is no rule that every flight go in a logbook.

The practical consequence is that a pilot who is already certificated and current is not breaking a rule by flying unlogged. They are only losing the record they would need the next time they have to prove something.

What goes in an entry you do log, per § 61.51(b): the date; total flight or lesson time; departure and arrival locations; type and identification of aircraft; the name of a safety pilot where § 91.109 requires one; the type of pilot experience or training; and the conditions of flight, day or night and actual instrument.

You must present your pilot certificate, medical certificate, logbook or any other record required by part 61 for inspection on reasonable request by the Administrator, an authorized NTSB representative, or any Federal, State or local law enforcement officer.

It depends on your age on the day of the examination, and the clock runs to the end of a month rather than to a date.

• Under 40: through the last day of the 60th month after the month of the exam.
• 40 or older: through the last day of the 24th month after the month of the exam.

Age at the exam fixes it. Turning 40 the week after a sixty month medical does not shorten it.

A first or second class certificate used for private privileges lasts the same 60 or 24 months. Duration follows the privileges you exercise, not the class you paid for.

An alternative to holding a current medical certificate. You must hold and possess a valid U.S. driver's license and comply with every medical requirement or restriction on it.

• At any point after July 14, 2006, have held a medical certificate issued under part 67. It may be expired, and you need not have held one continuously since.
• Receive a comprehensive medical examination from a State-licensed physician during the preceding 48 months, using the part 68 checklist.
• Complete the medical education course during the preceding 24 calendar months. Note the units differ: months for the exam, calendar months for the course.
• Keep the completed examination checklist and the course completion certificate available in your logbook.
• Your most recent medical certificate cannot have been suspended or revoked, your most recent special issuance cannot have been withdrawn, and your most recent medical application cannot have been denied.

The operating limits are the tradeoff. The aircraft must be authorized to carry no more than 6 occupants and have a maximum takeoff weight of no more than 6,000 lb, and it must be operated with no more than five passengers on board, which is a separate limit from the six occupants. No part of the flight may be more than 18,000 ft MSL, at an indicated airspeed exceeding 250 knots, or outside the United States without that country's authorization.

Only if it is a motor vehicle action. That one must be reported in writing to the FAA Civil Aviation Security Division within 60 days.

• A motor vehicle action is a conviction for violating a statute relating to operating a motor vehicle while intoxicated by alcohol or a drug, while impaired, or while under the influence; or the denial, suspension, cancellation or revocation of your driver's license for such a cause.
• A drug or alcohol conviction with no motor vehicle involved carries no § 61.15(e) report requirement, though it is still grounds for denial, suspension or revocation under § 61.15(a).
• Failure to report is itself grounds for denial, suspension or revocation of a certificate, rating or authorization.

The 60 days runs from the motor vehicle action, and the report is separate from whatever you disclose on your next medical application.

When the condition, or its treatment, would keep you from meeting the standards for the medical certificate the flight requires.

• Under § 61.53(a), you may not act as PIC or as a required pilot flight crewmember while you know or have reason to know of a medical condition that would make you unable to meet those standards.
• The same applies while you are taking medication or receiving other treatment that leaves you unable to meet them.
• For flights that need no medical certificate, the test under § 61.53(b) is whether the condition would make you unable to operate the aircraft safely.
• Under BasicMed and the other § 61.23(c) operations, a pilot with a U.S. driver's license is held to that same operate-safely test. One with only a medical certificate is held to the medical standards (§ 61.53(c)).
• The AIM names conditions that may be temporarily disqualifying, such as acute infections, anemia and peptic ulcer.
• Even a minor illness can impair judgment, memory, alertness and the ability to make calculations. A medication that controls the symptoms may itself decrease performance.

The trap is treating the expiration date as the answer. The certificate shows you met the standards on the day of the exam. § 61.53 asks whether you meet them today.

Three takeoffs and three landings within the preceding 90 days, as the sole manipulator of the controls.

• They must be in an aircraft of the same category, class, and type if a type rating is required.
• In a tailwheel airplane they must be to a full stop.
• In a nosewheel airplane by day, touch and goes count.

This is separate from the flight review. You can be well inside your 24 month review and still be prohibited from carrying anyone.

No, night currency requires 3 takeoffs and landings to a full stop in the past 90 days.

Night flight can be logged between the end of evening civil twilight and the beginning of morning civil twilight (usually ~30 minutes after sunset to ~30 minutes before sunrise). Takeoffs and landings only count towards night current between one hour after sunset and one hour before sunrise.

A minimum of 1 hour of ground training and 1 hour of flight training with an authorized instructor, logged with an endorsement.

• The ground portion reviews the current general operating and flight rules of part 91.
• The flight portion covers whatever maneuvers and procedures the instructor judges necessary to show you can safely exercise your privileges.
• It is due since the beginning of the 24th calendar month before the month you act as PIC, so a review in March 2026 carries you through March 2028.
• It must be given in an aircraft for which you are rated, by an authorized instructor.
• A flight instructor who has renewed the instructor certificate under § 61.197 within the same 24 calendar months need not do the 1 hour of ground training. Simply holding a current CFI certificate is not enough.

There is no pass or fail. The instructor either endorses it or gives you more training.

• A pilot proficiency check or practical test conducted by an examiner, an approved pilot check airman, or a U.S. Armed Force, for a certificate, rating, or operating privilege.
• A practical test conducted by an examiner for the issuance of a flight instructor certificate, an additional rating on one, or its renewal or reinstatement.
• One or more phases of an FAA-sponsored pilot proficiency award program.

Each resets the 24 calendar month clock from the month it was completed.

They lapse differently, and only one of them grounds you.

• Flight review expired: you may not act as PIC at all. You need the review, which means an hour of ground and an hour of flight with an instructor, and the endorsement.
• Passenger currency expired: you may still fly, just not with passengers. Do three takeoffs and three landings as sole manipulator, in an aircraft of the same category, class and type (if a type rating is required), and you are current again. In a tailwheel airplane they must be to a full stop.
• You do not have to be alone to do it. § 61.57(a)(2) lets anyone necessary for the conduct of the flight be aboard, so an instructor is fine, and it is limited to day VFR or IFR.
• Night passenger currency is separate. Pattern work by day does not restore it: you need three takeoffs and three landings to a full stop, between 1 hour after sunset and 1 hour before sunrise.

Neither requires a checkride, and neither involves the FAA.

Currency is what the regulations require. Proficiency is whether you can actually fly the flight in front of you. Currency is what is legal; proficiency is what is safe for your experience.

• Currency is a regulatory minimum: the flight review under § 61.56 and the recent flight experience under § 61.57, such as three takeoffs and landings in the preceding 90 days to carry passengers.
• Proficiency is the skill those minimums do not measure.
• Personal minimums bridge the two. They are limits set to your own current experience and proficiency, decided before the flight when there is no pressure to go.
• Example: the AFM allows a 15 kt crosswind, but your experience is 10 kt. 10 kt is your limit until a CFI gives you more.
• Mitigate with dual from a CFI or by flying with another pilot.
• Transfer the risk by having another pilot act as PIC, or cancel.

It starts before you touch the airplane. Review the logbooks, or a summary of airworthy status, for the required inspections and AD compliance, and confirm the required documents are aboard.

Then look at the whole airplane from a distance, walking up to it. Note misalignment of the landing gear and structure, distortion of the wings, fuselage or tail, skin damage, and any staining, dripping or puddles of fuel or oil.

Then the AFM/POH checklist, in the manufacturer's sequence. The things it is looking for:

• Cabin door hard to open or close, or latches that do not engage smoothly. That points at a misaligned doorpost, which can mean structural damage.
• Seats and belts: seats latched into the rails with the lock pins, rail holes not worn oval, belts and harnesses free of fraying and securely attached.
• Windows clean and free of cracks and crazing. A badly crazed window can go to near zero visibility with sun at the wrong angle.
• Fuel: confirm the quantity visually in each tank against the gauges, confirm grade and quality, and replace the caps securely. Any fuel stain warrants investigation, however old it looks, and on a wet wing the evidence runs along the rivet lines.
• Engine and propeller: cowling fasteners secure, spinner free of dents and cracks, blades free of nicks and erosion, no leaks inside the cowling, exhaust free of white staining, air filter unobstructed, and nothing loose inside such as rags, tools or nests.

You are confirming the airplane conforms to its type design and is in condition for safe operation, which is the definition of airworthy, and § 91.7(b) makes that determination yours.

Two separate tests, and the item has to pass both.

Is it required to be operative? Two gates come before the familiar four-item test.

• Does the aircraft have an approved MEL? If it does, you must use it, and the § 91.213(d) path is closed. § 91.213(d) opens "except for operations conducted in accordance with paragraph (a) or (c)" and applies only without an approved MEL.
• Is the aircraft eligible for the (d) path at all? § 91.213(d)(1) limits it to small non-turbine-powered airplanes, rotorcraft, gliders, lighter-than-air aircraft, powered parachutes and weight-shift-control aircraft.

Then the four-item test. The inoperative item must not be part of the VFR-day type certification, not required by the equipment list or KOEL, not required by § 91.205 or any other rule for the flight you are making, and not required operative by an airworthiness directive. Clearing all four, it may be removed or deactivated and placarded INOPERATIVE, with the maintenance recorded.

Is the airplane still in condition for safe operation? This one is yours regardless of the paperwork. § 91.7(b) makes the PIC responsible for determining whether the aircraft is in condition for safe flight, and for discontinuing the flight if an unairworthy mechanical, electrical or structural condition occurs.

• An item can clear the § 91.213 test and still ground the airplane in your judgment.
• A mechanic's signature this morning does not transfer the second test to the mechanic.
• Anything you cannot resolve goes to a mechanic before the flight, not after it.

Things the AFH says to treat as findings rather than cosmetics: fuel stains anywhere near a tank, a spinner with cracks, dents or missing fasteners, cowling fasteners showing black oxide film or flaking paint around the head, and a compass with a cloudy face, bubbles or a partly filled case, which renders it unusable.

One item is regulatory. Under § 91.107(a)(1) the PIC must ensure each person on board is briefed on how to fasten and unfasten their safety belt, and shoulder harness if installed, before takeoff. Under (a)(2) the PIC must also ensure each person has been notified to fasten them before moving on the surface, taking off, or landing.

The rest is the PHAK's SAFETY briefing, which is not a regulation but is what an examiner expects:

• Seat belts, shoulder harnesses, seat position
• Air vents, environmental controls, all airplane exits
• Fire extinguisher location and operation
• Exits and the emergency evacuation plan, and the location and contents of the survival kit
• Traffic, and talking: how you want them to point out traffic, and the sterile flight deck
• Your questions: invite them now rather than on the takeoff roll

Say two more things out loud: who touches the controls (nobody but you, unless you say so), and what you want them to do if you go quiet.

The briefing is also where passenger distraction gets managed before it starts, rather than during the climb.

The PIC carries the duty, not the passenger. § 91.107 puts the ensuring on the PIC in every paragraph.

• Brief each person on board on how to fasten and unfasten the belt, and the shoulder harness if installed, before takeoff.
• Notify each person to fasten them before moving on the surface, taking off, or landing. Taxi counts, which is the part most often missed.
• Each person must occupy an approved seat or berth with the belt, and harness if installed, properly secured during surface movement, takeoff and landing.

Two exceptions inside the rule:

• A person who has not reached their second birthday may be held by an adult occupying an approved seat or berth, provided the child does not occupy or use a restraining device.
• A person on board to engage in sport parachuting may use the floor as a seat.

Note what the rule does not say: it does not require belts to stay fastened en route. The separate § 91.105 requirement that a crewmember keep the belt fastened at their station does run enroute, and the shoulder harness requirement for a required flight crewmember applies during takeoff and landing.

The AFM/POH checklist governs the content. Where each one belongs in the sequence is general, and each placement stops a specific problem.

• Preflight inspection: the AFM/POH checklist, or a third-party checklist based on it, in the manufacturer's sequence. On a glass-panel airplane allow extra time, because the checklist is long and the items are easy to skim.
• Before-takeoff check: at the run-up position near the takeoff end, after taxiing. The taxi is what brings the oil temperature up to the minimum the AFM/POH requires before high power is applied.
• Taxi: some AFM/POHs specify taxi items. Where there are none, the taxi is still your chance to cross-check the flight instruments while moving.
• After-landing: only after the airplane is clear of the runway and stopped. Running it on the rollout takes attention away from controlling the airplane, which is the one thing that cannot wait.

Divide attention during the run-up. If the parking brake slips or toe brake pressure is inadequate for the power set, the airplane can move forward and go unnoticed if your eyes are inside. The AFH's practice is to split attention one item inside, then a look outside.

The AFM/POH start checklist governs: engines vary enough that there is no general procedure. What is general is the hazard management around it.

Before the starter:

• Clear the ramp, and behind the airplane too, of persons, equipment and anything thrust could pick up.
• Anticollision lights on at all times before start, plus position lights at night.
• Call "CLEAR" out of the side window and wait for a response before engaging the starter.
• Brakes depressed so the airplane cannot lunge forward, and one hand on the throttle to catch the initial engine speed.
• Starting power usually comes from the battery, but can come from external power through an external power receptacle. The AFM/POH has the procedure.

After it catches:

• Set about 1,000 rpm, or the AFM/POH figure, to let oil pressure rise and limit wear.
• Oil pressure should, in most conditions, reach the lower AFM/POH limit within 30 seconds. If it does not, shut down immediately: serious internal damage is likely.
• A continuous very high ammeter draw, or a starter-engaged light, means the starter stayed engaged. Also an immediate shutdown.
• Sounds, vibration, smells or smoke that do not match normal experience: shut down and investigate.

If it will not start:

• No more than 30 seconds of continuous cranking, then 30 seconds to 1 minute of cool-down. Starters are not continuous-duty motors and the heat damages them. A longer AFM/POH figure wins.
• The smell of burning insulation may indicate you have exceeded the recommended cranking time.
• After repeated failed attempts, stop and ask a qualified person why. Continuing to crank turns a no-start into a maintenance event.

Cold weather needs the proper seasonal oil grade and engine preheat as temperatures approach and fall below freezing.

Climb into it, dive away from it. In no wind the ailerons and elevator do almost nothing for directional control and are held neutral. They are not steering devices in any case.

• Quartering headwind. The upwind wing tends to be lifted. Upwind aileron up reduces the wind's lifting effect on that wing, and puts the downwind aileron down, adding a little lift and drag on the other side that further resists the rise.
• Quartering tailwind. With wind from behind, elevator down and upwind aileron down reduce the tendency of the wind to get under the tail and the wing and nose the airplane over. These positions also minimize weathervaning, so steering gets easier.

Steer with the rudder pedals, which drive the nosewheel. Only after full pedal deflection do you add brake to tighten a turn. Some makes have no nosewheel steering and turn on brakes alone.

Taxiing downwind, keep power to a minimum and use the brakes occasionally rather than riding them, or they overheat. Other than sharp slow turns, the throttle should be at idle before the brakes come on. Taxiing with enough power that the brakes control your speed is a common error.

Stop with the nosewheel straight to relieve side load and make moving off easier.

• Have the airport diagram out and in view the whole time, not consulted once and stowed.
• Get the taxi clearance, write it down, and read it back. A clearance to taxi is not a clearance to cross a runway; each runway crossing needs its own.
• Review the complete taxi plan against the diagram before moving, naming the turns and the runways you will cross.
• Eyes outside, scanning side to side and both near and far, assessing routing and conflicts as you go.
• Taxi at a speed where the throttle controls the movement, slow enough that closing it stops the airplane promptly. The requirements are positive control, recognizing hazards in time, and stopping or turning where you want without undue reliance on the brakes.
• Stop if clearance from anything is in doubt. It may take a tow or a ground crew, and that is the correct outcome.
• Scan the full length of the runway and the final approaches before entering or crossing any runway, even with a clearance.
• Use the taxi time to cross-check the flight instruments where the AFM/POH gives no taxi items: airspeed near zero, attitude indicator level with no flags, altimeter at field elevation, turn indicator showing the correct direction with the ball to the outside, directional gyro set and agreeing with the compass, VSI at zero.

Keep the flight deck sterile: no checklists, programming or unrelated conversation while the airplane is moving.

It is hearing the clearance you usually get instead of the one you were given. A pilot given the same taxi instructions repeatedly starts expecting them, and may not register that those instructions no longer apply. The AFH names it directly and calls it a human tendency to follow the same procedure over and over.

It takes missing one instruction or one turn to generate an accident.

What breaks it:

• Write the clearance down and read it back. Reading back what you wrote, not what you remember, is the check.
• Carefully review the complete taxi plan against the diagram before moving, even at an airport you know well. Familiarity is the condition that produces the bias, not a defense against it.
• Name the runways you will cross as part of that review, so a crossing you did not expect registers as a surprise.
• Treat a route or runway change as a reason to stop and re-plan, not as a minor amendment to absorb while rolling.
• If you lose track of where you are, stop and ask.

The same bias shows up in the departure runway. Confirm the runway numbers on the pavement agree with the compass and heading indicator before the takeoff roll.

A runway safety problem area or intersection on an airport, typically a complex or confusing taxiway/taxiway or taxiway/runway intersection.

• The confusion can be compounded by a miscommunication between a controller and a pilot, and can compromise an aircraft separation standard.
• The area may have a history of surface incidents, or the potential for them.
• On the airport diagram, a hot spot is a brown open circle or ellipse with a leader to its number, such as HS 1.
• The number matches a listing and description on the Hot Spot page in the front of the Terminal Procedures Publication.
• A taxiway crossing two runways that themselves intersect is a typical example.
• Before taxi, carry a current airport diagram and trace or highlight your route to the runway, noting the hot spots on it.
• If you are unsure of the route, ask ATC for progressive taxi instructions.

• The tower may not be able to see you. In some low visibility conditions, aircraft and vehicles may not be visible to the controller, so nobody can visually confirm you are following your taxi instructions.
• Tell the controller right away when you have difficulty, or at the first sign you are becoming disoriented.
• Withhold checklists and nonessential communication until the airplane is stopped with the brakes set, and give the taxi your entire attention.
• Airports with operations below 1,200 ft RVR may have a low visibility taxi plan (SMGCS) with additional lighting, markings and procedures, in two levels: below 1,200 ft to 500 ft RVR, and below 500 ft RVR.
• Geographic position markings, a numbered pink circle outlined in black and white, mark points along the designated low visibility taxi routes.
• Stop bar lights are a row of steady red lights across the taxiway at a runway, used below 1,200 ft RVR. Never cross a red stop bar, even with an ATC clearance.
• When ATC clears you, the stop bar goes off and the taxiway centerline lead-on lights come on. If the lead-on lights go out after you cross, hold your position and contact ATC.
• Clearance bar lights (three steady yellow) and runway guard lights (flashing yellow) make holding positions more conspicuous.

• Firm and free of debris, smooth pavement or turf, so the propeller does not pick up pebbles, dirt and sand and hurl them backward into the blades and the tail.
• Clear of other aircraft and the taxiway, with nothing behind that propeller blast can damage.
• Headed as nearly into the wind as possible. Air-cooled engines are tightly cowled and get far less cooling airflow on the ground, so prolonged ground running can overheat the cylinders well before the oil temperature shows anything.
• Roll forward slightly first so the nosewheel is aligned with the longitudinal axis.
• Oil temperature at the AFM/POH minimum before high power. The taxi usually supplies that, but verify it rather than assume.

What gets checked, per the AFM/POH:

• Fuel system set, on, correct tank selected
• Trim set for takeoff, including rudder and aileron trim where fitted
• Flight controls through their entire range, full deflection all directions. Not exercising the full range is a common error
• Engine: temperatures and pressures normal, magneto or FADEC check within limits, carburetor heat functioning, and a constant-speed propeller exercised
• Electrical: voltages in range and the battery showing a charge
• Vacuum, typically 4.8 to 5.2 inHg at 2,000 rpm, and gyros given time to spool up. A hurried taxi and run-up does not allow that
• Flight instruments reset for departure, with the directional gyro and compass in agreement
• Avionics set: frequencies, nav sources and courses, transponder code

Brief it out loud, even alone. The AFH says to make it aloud even when no one is there to listen, and to include a visual verification of the correct surface and direction to preclude a wrong-surface departure.

The AFH's own sample covers:

• Type of takeoff and the runway in use
• Wind direction and speed
• Rotation speed, the manufacturer's V_R
• Initial turn heading and initial altitude
• The engine failure plan, in three cases

The three cases are the point of the briefing:

That briefed turn-back altitude is a number you decide on the ground, for this airplane on this runway, and the AFH's phrasing is "I will only consider turning back." Deciding it in the air is how the impossible turn gets attempted.

Confirm the runway numbers on the pavement agree with the compass and heading indicator before the roll begins.

Remember them as ARROW:

• Airworthiness certificate, displayed at the cabin or cockpit entrance so it is legible to passengers or crew.
• Registration certificate.
• Radio station license, only for international flights. This one is an FCC requirement, not an FAA one.
• Operating limitations: the AFM/POH, placards, and markings.
• Weight and balance data, current for the aircraft as equipped. It is not a free-standing § 91.203 item: it rides along inside the AFM/POH, which § 91.9 requires.

The airworthiness certificate has no expiry date. It stays valid as long as the aircraft is maintained and inspected per the regulations, which is why it is the registration that people let lapse, not the airworthiness.

Not on its face, but it can end four ways. The certificate's own terms read: unless sooner surrendered, suspended, revoked, or a termination date is otherwise established by the Administrator, it is effective as long as maintenance, preventive maintenance and alterations are performed per parts 21, 43 and 91, and the aircraft is registered in the United States.

• It must be displayed at the cabin or cockpit entrance so that it is legible to passengers or crew.
• It stays with the aircraft when sold, unless it is sold to a foreign purchaser.
• The continuing conditions are the maintenance and the U.S. registration. Conformity to the type certificate is certified as of the date of issuance.

Yes. A Certificate of Aircraft Registration expires 7 years after the last day of the month in which it was issued, and the date is printed on its face.

• Renew by filing an Aircraft Registration Renewal Application, AC Form 8050-1B, with the fee, during the 6 months preceding the expiration date.
• The pink copy of the registration application, AC Form 8050-1, authorizes operation of an unregistered aircraft for no more than 90 days, and because the aircraft is unregistered it may not be operated outside the United States until the permanent certificate arrives.
• Expiration is not the only way it stops working. The certificate cannot be used for operations once the aircraft is registered in a foreign country, the registration is canceled on written request, the aircraft is destroyed or scrapped, ownership is transferred, or the holder loses U.S. citizenship. Ownership transfer is the one that catches a club.

It matters beyond the paperwork: the airworthiness certificate is effective only while the aircraft is maintained per parts 21, 43 and 91 and registered in the United States. This is also the document most often found expired, because unlike the annual nobody has to touch the airplane for it to lapse.

Two people, at different moments.

• The owner or operator is primarily responsible for maintaining the aircraft in an airworthy condition, including compliance with the ADs in part 39.
• The PIC is responsible for determining whether it is in condition for safe flight, and must discontinue the flight if an unairworthy mechanical, electrical, or structural condition occurs. § 91.7(a) binds the operator separately: no person may operate a civil aircraft unless it is in an airworthy condition.

Airworthy means two things at once: the aircraft conforms to its type certificate including any supplemental type certificates and ADs, and it is in a condition for safe operation. A rental aircraft signed off by a mechanic this morning can still fail the second test on your preflight, and that call is yours.

Remember them as AV1ATE. The letters read down the first column.

A privately flown airplane that nobody rents needs the annual, the transponder check if the transponder is used, and the ELT inspection. The 100-hour attaches to the commercial use, not to the airplane.

The scope is identical. What differs is who may sign it off and what triggers it.

• An annual must be performed by an A&P holding an Inspection Authorization, by the aircraft manufacturer, or by an appropriately rated repair station. It is required every 12 calendar months regardless of how little the aircraft flew.
• A 100-hour may be performed by any A&P, an appropriately rated repair station, or the manufacturer. It is required only when carrying persons for hire, or when giving flight instruction for hire in an aircraft the instructor provides. A CFI instructing in the student's own airplane does not trigger one.
• An annual can substitute for a 100-hour. A 100-hour cannot substitute for an annual unless it is done by someone authorized to do annuals and entered as one.

By not more than 10 hours, and only while en route to a place where the inspection can be done.

• The overfly is for repositioning, not for finishing the day's revenue flying.
• The excess counts against the next 100 hours. Go 6 hours over and the next inspection is due at 94.

There is no equivalent extension for an annual. When the 12 calendar months are up, the aircraft stops flying unless you get a special flight permit.

The aircraft is not airworthy and you may not simply fly it home.

• You cannot use the 10-hour overfly, which applies only to the 100-hour inspection.
• Options are to have the annual performed where the aircraft sits, or apply to the FSDO for a special flight permit to ferry it for the inspection.
• A special flight permit usually prohibits carrying passengers and specifies the route.
• The permit does not relieve AD compliance. All applicable ADs that are due must be complied with before the flight.

Checking the airworthiness and registration status before departure, not on arrival, is the whole lesson. The records live with the operator, so this is a phone call you can make the day before.

A legally enforceable rule issued by the FAA to correct an unsafe condition in a product. ADs are regulatory and shall be complied with unless a specific exemption is granted.

• One-time ADs are complied with once. Recurring ADs repeat at an interval.
• Emergency ADs are of a nature requiring immediate compliance prior to further flight.
• A Special Airworthiness Information Bulletin (SAIB) is the FAA's non-regulatory notice of an airworthiness concern. It is information, not a requirement.
• A manufacturer's service bulletin is likewise not mandatory under part 91 unless an AD adopts it.
• There is no provision to overfly the maximum hour requirement of an AD unless the AD itself says so. The 10-hour allowance on a 100-hour inspection has no counterpart here.

Operating with an overdue AD makes the aircraft unairworthy no matter how well it flies, and the compliance record lives in the maintenance logs rather than in the aircraft.

With the owner or operator, not in the aircraft. There is no general requirement to carry them. The one exception in the section: where a fuel tank is installed in the passenger or baggage compartment under part 43, a copy of FAA Form 337 must be kept on board.

They must show:

• A description of the work and the date completed
• The signature and certificate number of the person approving return to service
• Total time in service of the airframe, each engine, each propeller and each rotor
• The current inspection status, including time since the last required inspection
• Current status of ADs and safety directives: the method of compliance, the AD number and revision date, and for a recurring AD when the next action is due
• Current status of life-limited parts, and time since overhaul of items overhauled on a time basis
• Copies of the FAA Form 337 for each major alteration

Empty weight and center of gravity are not on that list. They live in the weight and balance section of the AFM/POH.

How long they are kept differs by type. The work records go until the work is repeated or superseded, or for 1 year. The status records above are retained and transferred with the aircraft when it is sold.

Before flying an unfamiliar rental, the records are how you confirm the annual and the transponder check.

Preventive maintenance, as listed in part 43 appendix A. Two conditions, and neither is about who is in the back seat:

• You must hold a pilot certificate other than student, sport or recreational.
• The aircraft must be one you own or operate, and it must not be used in air carrier service or qualify under parts 121, 129 or 135. A part 91 club airplane used for instruction for hire is still eligible.

Typical items:

• Servicing landing gear tires, wheel bearings, and shock struts
• Replenishing hydraulic fluid, changing oil
• Replacing safety belts, seats, side windows, and the bulbs, reflectors and lenses of position and landing lights
• Replacing spark plugs and cleaning or gapping them
• Servicing batteries

You must record it under § 43.9 with a description of the work, the date of completion, and your name, signature, certificate number and type of certificate held. The entry is what makes it legal maintenance rather than an undocumented modification.

A ferry permit, and formally a Special Airworthiness Certificate: authorization to fly an aircraft that does not currently meet airworthiness requirements but is safe for a specific flight.

Issued for purposes such as:

• Flying to a base where repairs or an inspection will be performed
• Delivering or exporting an aircraft
• Evacuating an aircraft from impending danger
• Operating an overweight aircraft for flight beyond its normal range over water or land where adequate landing facilities or fuel are not available

You apply to the local FSDO or a Designated Airworthiness Representative. Before it is issued, an FAA inspector may inspect the aircraft personally or require an A&P or a certificated repair station to inspect it to determine its safety for the intended flight, and that inspection is recorded in the aircraft records. The permit then carries conditions and limitations, often including no passengers and a specific route. It is the answer to "the annual expired and the airplane is at the wrong airport."

From § 91.205(b), remembered as A TOMATO FLAMES:

• Airspeed indicator
• Tachometer (for each engine)
• Oil pressure gauge (for each engine using a pressure system)
• Manifold pressure gauge (for each altitude engine)
• Altimeter
• Temperature gauge (for each liquid-cooled engine)
• Oil temperature gauge (for each air-cooled engine)
• Fuel gauge indicating the quantity in each tank
• Landing gear position indicator (if applicable)
• Anticollision lights (beacon or strobes, for small civil airplanes certificated after March 11, 1996 in accordance with part 23)
• Magnetic direction indicator (either magnetic compass or magnetometer)
• Emergency locator transmitter, if required by § 91.207
• Seat belts: an approved safety belt with a metal-to-metal latch, or other approved restraint, for each occupant 2 years of age or older

Two items the mnemonic leaves out. A shoulder harness for each front seat in small civil airplanes manufactured after July 18, 1978, and for all seats in those manufactured after December 12, 1986. And, for hire over water beyond power-off gliding distance from shore, flotation gear and one pyrotechnic signaling device.

If an anticollision light fails, you may continue to a place where it can be repaired or replaced.

The mnemonic is a memory aid. The regulation is the list, and it says "where applicable": an airplane with no retractable gear needs no gear indicator.

Everything required for day, plus the additions in § 91.205(c), remembered as FLAPS:

• Fuses (a spare set, or three of each kind required, if the aircraft uses them instead of circuit breakers)
• Landing light (only if operated for hire)
• Anticollision lights (beacon or strobes)
• Position lights (nav lights)
• Source of electrical power adequate for all installed equipment (e.g., an alternator or generator)

Required by § 91.215 in:

• Class A, Class B, and Class C
• Within 30 NM of a Class B primary airport, surface to 10,000 ft MSL, the Mode C veil
• Above the ceiling and within the lateral boundaries of Class B or Class C, up to 10,000 ft MSL
• At and above 10,000 ft MSL over the 48 contiguous states and DC, excluding airspace at and below 2,500 ft AGL
• Within 10 NM of an airport listed in appendix D, section 2, surface to 10,000 ft MSL, excluding airspace below 1,200 ft outside the lateral boundaries of that airport's surface area

An aircraft never certificated with an engine-driven electrical system, plus balloons and gliders, is excepted, but the veil exception comes with two conditions: the operation must be outside any Class A, B or C airspace, and below the lower of the Class B or C ceiling or 10,000 ft MSL. It does not let a Cub into the Class B.

If you have an operable transponder maintained per § 91.413, you must have it on with Mode C in all controlled airspace, not only where one is required. Class G is not covered.

Required by § 91.225 in:

• Class A, Class B, and Class C
• Within 30 NM of a Class B primary airport, surface to 10,000 ft MSL, the Mode C veil
• Above the ceiling and within the lateral boundaries of Class B or Class C, up to 10,000 ft MSL
• Class E at and above 10,000 ft MSL, excluding airspace at and below 2,500 ft AGL
• Class E over the Gulf of Mexico at and above 3,000 ft MSL within 12 NM of the coast

Class A requires 1090ES. Below 18,000 ft MSL, either 1090ES or 978 UAT satisfies the rule.

ADS-B Out is what the regulation requires. ADS-B In, which puts traffic and weather in the cockpit, is never required.

Most aircraft must have one, inspected every 12 calendar months.

• Batteries must be replaced or recharged after 1 hour of cumulative use, or when 50 percent of their useful life has expired.
• The replacement date must be legibly marked on the outside of the transmitter and recorded in the maintenance record.
• An aircraft may be operated for up to 90 days with the transmitter temporarily removed for inspection, repair, modification or replacement, but only if the aircraft records carry an entry giving the date of initial removal, the make, model, serial number and reason, and a placard in view of the pilot reading "ELT not installed." An inoperative ELT that is still bolted in is not this exception.
• Also excepted: aircraft in training operations conducted entirely within a 50 NM radius of the airport the flight began from, and aircraft equipped to carry not more than one person.

The older 121.5 MHz units are no longer monitored by satellite: Cospas-Sarsat terminated reception of 121.5 MHz and 243.0 MHz in 2009. A 406 MHz ELT is what actually brings anyone to you, and § 91.207 imposes no frequency requirement.

Possibly. § 91.213(d) has four numbered conditions, and the first is about the aircraft, not the item: the deferral path is available to small non-turbine-powered airplanes, rotorcraft, gliders and lighter-than-air aircraft operated under part 91. A turbine airplane does not get here at all.

Then the inoperative item must not be:

• Part of the VFR-day type certification equipment for the aircraft
• Required on the aircraft's equipment list or Kinds of Operations Equipment List (KOEL)
• Required by § 91.205 or any other rule for the flight being conducted
• Required to be operational by an airworthiness directive

Then it must be either removed with the cockpit control placarded and the maintenance recorded under § 43.9, or deactivated and placarded "Inoperative." Where deactivation involves maintenance, and removal always does, it has to be done by certificated maintenance personnel and recorded under part 43.

Finally, the pilot or a mechanic determines it does not constitute a hazard. A placard alone is not the authorization; it is the last step of one.

The deferral is not indefinite. § 91.405(c) requires the item to be repaired, replaced, removed or inspected at the next required inspection.

An approved list of equipment that may be inoperative for a specific aircraft, with the conditions attached.

• The FAA develops the Master MEL for aircraft in current use. On written request the local FSDO issues the make and model MMEL with a letter of authorization and the preamble.
• The operator then writes operations and maintenance procedures from the MMEL, and that combination becomes the operator's MEL.
• Four documents must be on board during each operation: the MEL, the LOA, the preamble, and the procedures document.
• Together the MEL and that letter act as a supplemental type certificate.
• Once an MEL exists for the aircraft, you must use it. The § 91.213(d) path is no longer available.

Three classes of equipment may never be on an MEL, per § 91.213(b): equipment that is part of the VFR-day type certification and essential for safe operation, equipment an airworthiness directive requires to be operable, and equipment required for the specific operation by part 91.

Most trainers have no MEL, which is why the § 91.213(d) path matters far more in a typical trainer than the MEL does.

For an airplane, considering wind and forecast weather conditions, enough fuel to reach the first point of intended landing, and then, assuming normal cruising speed:

• 30 minutes of reserve at normal cruise, by day
• 45 minutes by night

The rule requires you to consider the wind; what it does not forgive is the forecast being wrong. It is a legal minimum, not a plan, and it makes no allowance for a headwind stronger than forecast, a closed runway, or a hold. A rotorcraft needs only 20 minutes.

Fuel exhaustion and starvation are preventable on the ground, which is where the margin above the minimum gets decided.

Use the grade in the AFM/POH and on the filler placard. Grades are dyed so you can confirm what went in: 80 red, 100 green, 100LL blue, jet fuel clear or straw.

• If the proper grade is not available, use the next higher grade. Never a grade lower than recommended: it invites detonation, driving cylinder head and oil temperatures past their normal ranges.
• Automobile gas must never be used in an aircraft engine unless the aircraft has been modified under a Supplemental Type Certificate.
• Jet fuel in a piston engine is catastrophic, and the engine may run briefly before failing.

Color is a weaker check than it looks: 100VLL is blue and virtually indistinguishable from 100LL. Guard against misfueling by watching the truck, checking the placard, and sumping after the uplift. A piston aircraft refueled from a jet truck is a known accident chain.

Sump every drain, including both wing tanks and the gascolator, into a clear tester.

• Water sits at the bottom as clear beads or a distinct layer. It is denser than avgas.
• Color confirms the grade: 100LL is blue, 100 is green, jet fuel is clear or straw and smells of kerosene.
• Sediment and debris settle out visibly.

Sump after refueling and after the aircraft has sat, since water needs time to settle. If you find water, keep draining until it is clear, then check again, because one clean sample after a wet one proves nothing.

A reference condition that instruments and performance charts are built around, established by ICAO and also called the ISA.

At sea level:

• 29.92 inches of mercury, which is 1013.2 millibars
• 15 °C, or 59 °F

The standard lapse rates:

• Temperature decreases 2 °C per 1,000 ft up to 36,000 ft, above which it is considered constant to 80,000 ft. The temperature at the tropopause is -56.5 °C.
• Pressure decreases approximately 1 inHg per 1,000 ft of altitude gain to 10,000 ft.

Real conditions are almost never standard. That is why you set an altimeter and compute density altitude: both correct an instrument or a chart back to the air you are actually flying in.

A lapse rate is the rate temperature decreases with altitude.

• Average, or standard: 2 °C per 1,000 ft (3.5 °F). This is the atmosphere's typical overall rate and the one in the standard atmosphere.
• Dry adiabatic: 3 °C per 1,000 ft (5.4 °F). The rate a parcel of unsaturated air cools as it rises.
• Moist adiabatic: 1.1 to 2.8 °C per 1,000 ft (2 to 5 °F). Slower, because condensing water vapor releases latent heat into the parcel.

Comparing a parcel's rate to the surrounding air's is how stability is determined. A parcel that stays warmer than its surroundings keeps rising.

Moist air is generally less stable than dry air, because cooling more slowly means it must rise farther before its temperature matches the air around it.

Stability is the atmosphere's ability to resist vertical motion.

• Stable air makes vertical movement difficult. Small disturbances dampen out and disappear.
• Unstable air lets small vertical movements grow, producing turbulent airflow and convective activity.

What each gives you:

• Stable: stratiform clouds, steady precipitation, smooth air, poor visibility, and fog or haze trapping below.
• Unstable: cumuliform clouds, showery precipitation, turbulence, good visibility between the showers, and the potential for thunderstorms.

Cool, dry air is very stable. The greatest instability occurs when air is moist and warm, which is why afternoon thunderstorms are routine in the tropics in summer.

A layer where temperature increases with altitude instead of decreasing, which is the reverse of normal.

Inversions form most often on clear, calm nights as the ground radiates heat away and cools the air directly above it. They also occur aloft where warm air overruns cold air.

What it means in the airplane:

• The layer is very stable, so expect smooth air within it.
• Moisture, haze and smoke are trapped below, so visibility beneath the inversion is often poor.
• Wind shear is common at the top of the layer, where calm surface air meets stronger wind above.

The dew point is the temperature at which air becomes saturated. The spread between temperature and dew point tells you how close the air is to producing visible moisture.

• When air reaches saturation with temperature and dew point close together, the PHAK says fog, low clouds and precipitation are highly likely.
• A closing spread means conditions are deteriorating, particularly with clear skies and light wind at night.
• A wide spread means the air is dry and clouds are unlikely at the surface.

You can also estimate the base of convective cloud. Rising unsaturated air cools at 5.4 °F per 1,000 ft while the dew point falls at only 1 °F per 1,000 ft, so they converge at 4.4 °F per 1,000 ft.

The PHAK's worked example: 85 °F with a dew point of 71 °F gives a 14 °F spread, and 14 divided by 4.4 is 3.18, putting the cloud base at 3,180 ft AGL.

The wind at 2,000 ft AGL is 20° to 40° to the right of the surface wind, and faster. With no winds aloft information, that is your rough estimate.

• Friction is the cause. Within 2,000 ft of the ground it slows the moving air, and the frictional force also diverts the wind from its path.

• The shift is greatest over rough terrain and least over flat surfaces such as open water.

• Reported surface wind can differ noticeably from what you find climbing out of the pattern.

• A crosswind on takeoff is often a different crosswind by the time you are on downwind.

Above the friction layer the air flows in response to pressure gradient and Coriolis alone, which is why winds aloft forecasts and the surface report are answering different questions.

Unequal heating of land and water, with the circulation reversing between day and night.

• Sea breeze, daytime: land heats faster than water. Air over the land rises and is replaced by cooler, denser air flowing in from over the water, giving an onshore wind.
• Land breeze, nighttime: land cools faster than water. Air over the water is now warmer and rises, replaced by cooler air flowing off the land, giving an offshore wind.

Expect a wind shift and often a line of convective clouds where the sea breeze front pushes inland during the afternoon.

The same uneven heating drives convective currents anywhere, and the discriminator is barren versus vegetated, not light versus dark. Barren ground, pavement, rock and sand absorb heat quickly and produce updrafts; water and thick vegetation absorb it slowly and produce downdrafts. On final, rising air off bare terrain can balloon you past the spot, and an approach over water or heavy vegetation can land you short.

Three ingredients, per the PHAK:

• Adequate water vapor
• Condensation nuclei, miniscule particles of dust, salt or smoke
• A method of cooling the air to its saturation point

The nuclei matter because they provide a means for the moisture to change from one state to another.

The PHAK gives four ways air reaches saturation:

• Warm air moving over a cold surface
• Cold air and warm air mixing
• Air cooling at night through contact with the cooler ground
• Air being lifted or forced upward, losing heat as it expands at 3 °C per 1,000 ft while unsaturated

By the height of their bases, plus a separate group for vertical development.

The prefix tells you the rest. Nimbus means precipitation, alto means middle, cirro means high.

The trap with dust is the reported visibility. It is measured horizontally at the surface, and slant-range visibility is worse, so you may not be able to pick out the airport from above even when 3 SM or more is reported.

An air mass takes on the temperature and moisture of the surface it sits over for an extended period. When it moves and meets an air mass with different characteristics, the boundary between them is a front.

The four types, named for the temperature of the advancing air relative to the air it replaces:

• Warm: warm air overtaking cooler air. Shallow slope, widespread stratiform cloud, steady precipitation, poor visibility, gradual changes over a long distance.
• Cold: cold air overtaking warmer air. Steep slope, a narrow band of cumuliform cloud, showers or thunderstorms, and a rapid clearing with good visibility behind.
• Stationary: neither air mass displacing the other. Conditions persist, sometimes for days.
• Occluded: a fast moving cold front catches a slow moving warm front, and there are two kinds. In a cold front occlusion the advancing cold air is colder than the air ahead of the warm front. In a warm front occlusion the air ahead is colder, so the cold front rides up and over the warm front; if the air forced aloft is unstable, this one is the more severe. As the occluded front approaches, warm front weather prevails, immediately followed by cold front weather.

An approaching front of any type means the weather is about to change. The reliable clues are a wind shift, a temperature change, and a pressure change.

Three ingredients

• Sufficient moisture
• An unstable lapse rate
• A lifting action (a front, terrain, surface heating, or convergence)

Three stages

Hazards

Severe turbulence, wind shear and microbursts, hail (which can be thrown miles outside the cloud), severe icing, lightning, heavy rain, tornadoes, and a complete loss of visibility.

What it means for us

Never fly under a cell, since that's where the shear and hail live. Avoid anything severe or with an intense echo by at least 20 NM. Circumnavigate areas of heavy coverage rather than picking through them. And remember that an embedded cell in IMC gives you no visual warning at all.

A narrow band of active thunderstorms. It often develops on or ahead of a cold front in moist, unstable air, though it may also develop in unstable air far from any front, and in summer it can form as much as 200 NM ahead of a strong cold front. The PHAK calls it the single most intense weather hazard to aircraft.

• Because the cells are cumulonimbus driven by rising air currents, they are extremely turbulent. An airplane entering one can meet updrafts and downdrafts exceeding 3,000 fpm.
• They can also produce large hailstones, damaging lightning, tornadoes and large quantities of water.
• The line often runs for hundreds of miles with no usable gap, which is what distinguishes it from isolated airmass thunderstorms.

You go around it or you wait. Flying below a squall line is hazardous and over the top is not an option in a light airplane, so if you cannot go around it, stay on the ground until it passes.

Distance is not the same as clearance. Shear turbulence has been encountered several thousand ft above and 20 NM laterally from a severe storm, and any cloud connected to a severe thunderstorm carries a threat of violence.

A strong, concentrated downdraft that spreads outward in all directions from the downdraft center when it reaches the surface. The AWH calls it the most severe type of wind shear.

• Horizontal diameter less than 2.5 miles, nominal depth 1,000 ft
• Lifespan of 5 to 15 minutes
• Downdrafts of up to 6,000 fpm
• Headwind losses of 30 to 90 knots, seriously degrading performance

It is most dangerous when climbing after takeoff or approaching to land, because you are slow and a major change of wind velocity can lead to a loss of lift.

An intense rain shaft may mark it, but virga or a ring of blowing dust is sometimes the only visible clue. More than one can occur in the same weather system, so encountering one is reason to expect another.

A sudden, drastic change in wind speed or direction over a very small area. It can be vertical or horizontal, and it subjects the airplane to violent updrafts and downdrafts.

It can occur at any altitude, but low-level shear is especially hazardous because of your proximity to the ground. The PHAK associates it with:

• Passing frontal systems
• Thunderstorms
• Temperature inversions
• Strong upper level winds, greater than 25 knots

Why it bites: a tailwind changing quickly to a headwind increases airspeed and performance, while a headwind changing to a tailwind decreases both. On an approach the second case leaves you low, slow and with the power already reduced.

A standing wave that forms when stable air is deflected upward by a ridge. Air moving nearly perpendicular to the barrier is lifted and accelerated over the crest and down the lee slope, setting up a wave downwind.

• A wave existing is not by itself a hazard. The danger depends on the strength of the wave and whether part of it breaks into turbulence, which in the extreme can cause structural damage.
• The rotor zone is the worst of it: near or below ridge level on the downwind side, beneath a wave crest. The AWH calls this an area of potentially severe-to-extreme wind shear and turbulence.
• Lenticular and rotor clouds mark the wave when there is enough moisture. A rotor cloud can look like an innocuous cumulus from a distance.

Rotors are especially dangerous at low altitudes, particularly during takeoff and landing, where the airplane is slow and in a high-drag configuration.

Severe wind events can occur with little or no visual warning, so absence of lenticular cloud is not evidence the wave is absent.

The lowest altitude over a location at which the air temperature reaches 0°C, also called the height of the 0°C constant-temperature surface.

• Freezing level graphics: an hourly analysis of the lowest freezing level in MSL, plus model forecasts at set times ahead. White on the analysis means the surface and the whole atmosphere are below freezing.
• AIRMETs: the range of freezing levels over an area, any areas with more than one, and the lowest at 4,000 ft intervals.
• Low-level significant weather chart: freezing levels as blue dashed lines in hundreds of feet MSL, from 4,000 ft at 4,000 ft intervals.
• GFA Tool and the Flight Service Interactive Map include freezing levels.
• Upper air forecasts give model freezing levels at selected heights.
• PIREPs include it when a pilot reports it.

There can be more than one. Where the surface is below freezing there may be multiple freezing levels aloft, which the analysis marks with hatching or spots.

The trap is estimating it with the standard lapse rate. The actual lapse rate seldom matches it, and the low-level air is often dry adiabatic, so the estimate can be in error.

No. The airplane must be thoroughly cleaned and free of frost before flight.

• Frost disrupts the flow of air over the wing and can drastically reduce the production of lift.
• It also increases drag. Reduced lift with added drag can leave the airplane unable to take off.
• Dew, by contrast, poses no threat. The difference is whether the surface temperature was below freezing when the moisture was deposited.

The specific hazard is not weight: the actual weight of ice on an airplane is insignificant compared to the airflow disruption it causes. Wind tunnel and flight tests show that accumulations on the leading edge or upper surface no thicker or rougher than a piece of coarse sandpaper can reduce lift by 30% and increase drag by up to 40%. Polishing frost smooth is not a substitute for removing it: the AIM says smooth or polished frost on a lift-generating surface is not an acceptable condition for departure.

Taken field by field:

• KPWK Chicago Executive. 121853Z issued on the 12th at 1853 Zulu.
• 27018G26KT wind from 270 true at 18 knots, gusting 26.
• 4SM four statute miles visibility.
• -RA BR light rain and mist. The minus is light, no sign is moderate, a plus is heavy.
• BKN012 OVC025 broken at 1,200 ft AGL, overcast at 2,500 ft AGL. The ceiling is the lowest broken or overcast layer, so 1,200 ft.
• 08/06 temperature 8 °C, dew point 6 °C, a 2 °C spread.
• A2991 altimeter 29.91 inches.
• RMK AO2 an automated station that can distinguish precipitation type.

A 1,200 ft ceiling with 4 miles is MVFR: a ceiling of 1,000 to 3,000 ft or visibility of 3 to 5 SM.

• Automated Terminal Information Service (ATIS) - Local weather data combined with non-weather operational details
• Automated Surface Observing System (ASOS) - Continuous, automated weather reporting with type/intensity of precipitation and fog/haze
• Automated Weather Observing System (AWOS) - Continuous, automated weather that reports basic meteorological data.

Marginal VFR. It's weather that's approaching IFR, but is still legally VFR - 1,000-3,000 ft ceilings and/or 3-5 SM visibility. If you are instrument rated, it's a good idea to file IFR in these conditions.

A pilot report of actual weather conditions

• UA (routine) and UUA (urgent)
• UA includes routine reports such as cloud tops, bases, and light conditions.
• UUA includes urgent reports such as severe turbulence, severe icing, and low-level wind shear.

Aviation Weather Center and weather briefing products

Transmit the conditions to ATC, e.g., "Chicago Approach, Archer 12345. Cloud bases were at 2,000 ft MSL and tops were at 4,000 ft MSL."

Routine PIREP over EAU, time 2247Z, flight level 340, aircraft type CRJ-700, occasional turbulence and light chop

• TAF issued for KBWI airport on the 14th at 1735Z, valid from the 14th at 1800Z to the 15th at 2400Z, winds 210 at 9 gusting 17 knots, visibility greater than 6 SM, scattered clouds at 5,000 and broken at 25,000
• From the 14th at 2100Z winds 210 at 13 knots gusting 23 knots, visibility greater than 6 SM, light rain showers, scattered clouds at 5,000 and broken at 8,000
• 30% probability between the 14th at 2200Z and the 15th at 0200Z variable winds at 15 knots, gusting 35 knots, visibility 4 SM, thunderstorms and rain, overcast cumulonimbus clouds at 4,000
• From the 15th at 0400Z winds 240 at 6 knots, visibility 6 SM, light rain showers, broken clouds at 4,500

A concise statement of the expected conditions significant to aviation, for a specified period, within 5 SM of the center of the airport's runway complex. It is a terminal forecast, not an area forecast.

• Issued four times a day, every 6 hr, at 0000, 0600, 1200 and 1800Z, and amended as needed. Some locations routinely issue an amendment 3 hr after the initial.
• Most run 24 hr; some major airports run 30 hr.
• It uses the same weather codes as a METAR, so if you can read one you can read the other.
• Temperature is not in the NWS TAF. If you need a forecast temperature, that comes from the LAMP/MOS product.

• The format is DDff±TT: direction in tens of degrees (true), speed in knots, and temperature in °C.
  • 1312+05 is wind 130° at 12 kt, +5 °C.
• 9900 means light and variable, less than 5 kt.
• Speeds of 100 to 199 kt are coded by adding 50 to the direction and subtracting 100 from the speed, so 7525 decodes as 250° at 125 kt. Any direction pair above 36 is this case.
• Above 24,000 ft, temperatures are always negative and the minus sign is dropped.
• No winds are forecast for a level within 1,500 ft of the station elevation, and no temperatures within 2,500 ft.
• The directions are true, not magnetic, so correct for variation before comparing them to a heading.

A set of web-based displays on aviationweather.gov giving a picture of the weather that may affect a flight. Coverage is the CONUS, the Gulf of America, the Caribbean, portions of the Atlantic and Pacific, Hawaii and Alaska.

The two static graphics below are provided for 3, 6, 9, 12, 15, and 18 hours, with a CONUS view and several regional views.

Two panels carry most of what a VFR pilot needs:

• Aviation Surface Forecast: obscurations, visibility, weather phenomena, and winds including gusts. Overlaid with AIRMET Sierra for IFR conditions and AIRMET Tango for sustained surface winds greater than 30 kt.
• Aviation Clouds Forecast: cloud coverage, bases, layers and tops in hundreds of feet MSL. Overlaid with AIRMET Sierra for mountain obscuration and AIRMET Zulu for icing.

It replaced the textual area forecast for the CONUS. It does not replace reading the TAFs, because a graphic covering an area will not show one field going down.

A forecast of the potential for thunderstorms over the next eight days, issued by the NWS Storm Prediction Center (SPC) in narrative and graphical form for the contiguous U.S.

• It covers both severe and non-severe (general) convection.
• Severe means a tornado, wind gusts of 50 kt or greater, or hail 1 inch or greater in diameter.
• Areas are rated, in increasing order, as marginal (MRGL), slight (SLGT), enhanced (ENH), moderate (MDT) or high (HIGH) risk of severe weather, based on a percentage probability.
• Days 1 to 3 also show areas of general thunderstorms (TSTM).
• It is not a watch. A severe thunderstorm or tornado watch means severe weather is possible during its valid time. A warning means it has been observed or is expected within the hour.

Advisories for en route weather that may be hazardous, especially to light aircraft. Three categories, and the letters are what you will be asked for:

Timing comes in two forms. Over the CONUS they are displayed graphically, sometimes called G-AIRMETs, valid at discrete times no more than 3 hr apart out to 12 hr. The text bulletin behind them is issued every 6 hr (0245, 0845, 1445 and 2045Z) and is valid 6 hr. Unscheduled AIRMETs are issued when conditions occur that were not forecast.

The difference from a SIGMET is severity and audience: moderate conditions hazardous to light aircraft, against severe conditions hazardous to all aircraft.

Advisories for non-convective en route weather hazardous to all aircraft, not just light ones. Unscheduled: issued any time the criteria are occurring or expected within a 4 hr period.

Inside the CONUS, the criteria are:

• Severe or greater turbulence
• Severe icing
• Widespread dust storm
• Widespread sandstorm
• Volcanic ash

A CONUS SIGMET is valid up to 4 hr, and is reissued at least every 4 hr while the condition continues.

Outside the CONUS the list also includes thunderstorms (obscured, embedded, widespread, squall line, isolated severe) and tropical cyclones, and volcanic ash and tropical cyclone SIGMETs can be valid up to 6 hr.

Convective weather inside the CONUS gets its own product, the Convective SIGMET.

The thunderstorm advisory, issued for the CONUS instead of a SIGMET. Issued every hour at 55 minutes past the hour, valid 2 hr.

What triggers one:

• Tornadoes
• Severe hail
• Severe surface winds
• Squall lines
• Widespread thunderstorm activity
• Embedded or severe thunderstorms

Any Convective SIGMET implies severe or greater turbulence, severe icing and low-level wind shear, so those are never listed separately.

The polygon is a snapshot at the issuance time. During the valid period the area moves along the vector given in the text, so a fast-moving line will not be where the graphic drew it.

Every 3 hr, but it takes around 90 minutes to create them, meaning they're always a little out of date.

• Isobars, which indicate lines of equal pressure.
• The numbers are the pressure (in millibars).

• A high-pressure system, with air generally sinking, moving outward, and rotating clockwise
• It results in stable conditions such as smooth air and few clouds.

• A low-pressure system, with air generally rising, moving inward, and rotating counterclockwise
• It results in unstable conditions such as rain, wind, icing, and even thunderstorms.

• An elongated area of relatively high pressure
• It brings clear skies and light winds.

• A trough, which is an elongated area of relatively low pressure.
• It brings gusty winds, clouds, and precipitation.

• A cold front, where a cold air mass advances under and lifts a warmer air mass.
• Weather changes are abrupt and typically more severe, including thunderstorms, heavy rainfall, and a temperature drop.

• A warm front, where a warm air mass advances over a cooler air mass.
• Weather changes are slow, and may include light rain, drizzle, and a temperature rise.

• A stationary front, where two air masses meet but neither advances significantly.
• Weather tends to persist and can produce low IFR conditions, including rain.

• Looks similar to a stationary front, but is entirely purple
• It happens when a cold front, which typically moves faster, catches up to a warm front moving in the same direction.
• When the cold front is colder than the air in front of the warm front ("cold front occlusion"), it lifts the warm air up and generates heavy rainfall.
• When the cold front is warmer than the air in front of the warm front ("warm front occlusion"), it slides in between the warm and colder air and generates gradual weather changes, including prolonged periods of rain.

Short-Range Surface Prog Charts are the forecast counterpart to a surface analysis chart: same kind of picture, but of conditions expected rather than observed.

• Produced by the Weather Prediction Center for the CONUS and coastal waters, covering a multiday period.
• They plot surface pressure systems, fronts and precipitation, combining WPC forecasts of fronts, isobars and highs and lows with the National Digital Forecast Database.
• The period is divided into selected valid times, and each chart is a snapshot of what is expected at its own valid time, not a summary of the span.
• Precipitation is shown by type and probability: rain green, snow blue, mixed purple, freezing rain red, each in a light shade for chance (25% to under 55%) and a dark shade for likely (55% or more). Thunderstorms are red diagonal hatching.

• Standard - The full picture, for when you haven't looked at anything yet. It covers adverse conditions, VFR flight not recommended when applicable, the synopsis, current conditions, enroute and destination forecasts, winds aloft, NOTAMs, and ATC delays.
• Abbreviated - An update to a briefing or data you already have. Tell the briefer what you've already seen and when you saw it.
• Outlook - For a departure 6 or more hours away. Forecast information only.

All three are also available in flight via Flight Service. You can also get a compliant briefing by self-briefing with qualified sources (e.g., ForeFlight) because § 91.103 is about having the information, not about how you got it.

Datalink weather is old by the time you see it, and it is for strategic decisions, not for picking a way through a storm.

• Every product has latency. NEXRAD imagery may be 15 to 20 minutes older than the time on the display, so check the product time and use it knowing it shows where the weather was.
• Strategic, not tactical. Use it for route selection to avoid a weather area entirely, typically 20 minutes or more ahead. Do not use it as the sole means of negotiating a path through a thunderstorm area, typically under 3 minutes ahead.
• It does not replace a preflight briefing, or ATC and Flight Service in flight.
• A clear radar display does not mean clear weather. Radar does not detect clouds or fog.
• Onboard radar attenuates. An airplane's 3 cm radar loses energy in heavy precipitation, so it typically shows only the leading edge of extreme echoes.

Act early, while there are still options. The hazard is continuing VFR into deteriorating conditions, which remains a leading cause of fatal general aviation accidents.

• Make the decision before the margin is gone. A 180° turn puts you back into air you have just proved was flyable.
• Divert to a suitable airport while you still have the ceiling and visibility to get there.
• Use ATC. Request flight following, radar vectors, or declare an emergency if needed. An emergency declaration costs paperwork at worst.
• Climb or descend only if that puts you clearly in better conditions, and never into cloud.

Set the limits on the ground, as a personal minimum with a hard number for ceiling and visibility. Deciding in flight, with a destination in mind and fuel burning, is the condition under which the decision is made badly.

If you end up in it anyway, it is an emergency. Anytime you cannot hold the airplane's attitude by reference to the natural horizon you are in IMC, whatever the prevailing weather, and the AFH says to accept it as a genuine emergency. Three steps, in order:

1. Recognize and accept it, and act immediately.
2. Keep control of the airplane. Wings level on the attitude indicator. If you must turn, use the smallest practical bank and in no case more than 10°, turning a few degrees at a time and returning to level if the heading change is large. To descend, reduce power in increments of 100 rpm or 1 inHg, keep the rate of descent at or below 500 fpm, and hold the pitch no lower than one bar width below level.
3. Get help to put the airplane safely on the ground.

• NOTAMs
• Weather reports and forecasts
• Known ATC delays
• Runway lengths
• Alternatives available
• Fuel requirements
• Takeoff and landing distances

Chart the course first, then compute from it: plot the course on a sectional, pick checkpoints, measure distances, get the weather, and work out headings, time and fuel.

Choosing an altitude balances several things against each other:

• Terrain and obstacles, with enough margin to clear them and to be received by the facilities you plan to use.
• Glide distance. Higher gives you more choices if the engine quits, which matters most over inhospitable ground.
• § 91.159 VFR cruising altitudes, which apply in level cruise more than 3,000 ft above the surface and are set by magnetic course.
• Wind. The winds aloft forecast can make a 2,000 ft difference worth several knots of groundspeed either way.
• Weather and cloud clearance, since the altitude has to keep you legal under § 91.155 as well as clear of terrain.

What to compute, and these are the ACS's own list: time, climb and descent rates, course, distance, heading, true airspeed and groundspeed; estimated time of arrival including the conversion to UTC; and fuel requirements including reserve. Work the fuel consumption rate against the estimated time so refueling points are part of the plan rather than a surprise.

Two currency traps. A sectional can be up to 6 months old, and the effective date is printed on the front. Where the back of the chart and the Chart Supplement disagree, the Chart Supplement is newer and wins.

Then the airplane. Weight and balance from the latest data in the approved AFM, and takeoff and landing distances for the fields you are actually using, which § 91.103 requires for any flight.

Within the continental U.S. a VFR flight plan is not normally required, but it is strongly recommended: it is what causes somebody to look for you.

When one is required:

• Into an ADIZ: a DVFR flight plan, except for DoD and law enforcement flights.
• VFR to an international destination: a filed and activated flight plan.
• The Washington DC Special Flight Rules Area carries additional requirements of its own.

Filing. With Flight Service or an equivalent service, on FAA Form 7233-4. File a separate plan for each leg of a stopover flight, and list surveillance equipment, because ATC radar history helps locate a downed aircraft.

Activating is on you, by radio or other electronic means.

• U.S. towers do not routinely activate VFR flight plans. Talking to the tower is not activating anything.
• An assumed departure time activates it automatically. Depart late without updating it and search and rescue works from the assumed time.

Closing is entirely on you, and this is where it differs from IFR.

• Landing at a towered airport does not close a VFR flight plan. Control towers do not close VFR or DVFR flight plans, because they have no way to know a given VFR aircraft is on one.
• An IFR flight plan to a towered airport is closed automatically on landing. Carrying that habit across is the trap.
• Close with the nearest FSS. If none is available, ask any ATC facility to relay the cancellation.
• Fail to report or cancel within 30 minutes after your ETA and search and rescue procedures start.

Position reports are not required, but periodic calls to Flight Service are good practice.

Flight Service Stations are air traffic facilities. What they do:

• Pilot briefings
• Flight plan processing: activating and closing yours, and starting a search if you do not
• En route flight advisories
• Search and rescue services
• Assistance to lost aircraft and aircraft in emergency situations
• Relaying ATC clearances
• Processing NOTAMs
• Broadcasting aviation weather and aeronautical information

On the ground: 1-800-WX-BRIEF in the CONUS, Hawaii and Puerto Rico, 1-833-AK-BRIEF in Alaska, or 1800wxbrief.com.

In the air you find the frequency on the sectional, and there are two places to look:

• A heavy line box around a NAVAID box marks a Flight Service Station. The frequencies it works are printed above the box.
• A thin line box is a Remote Communications Outlet (RCO), an FSS radio providing voice communications away from the station itself. Frequencies above a thin line box are remoted to the NAVAID site.
• A thin line box with no frequencies means no FSS frequencies are available there.

Reading the frequencies:

• They transmit and receive unless followed by a letter.
• R means receive only: the station listens on that frequency but answers over the NAVAID's voice channel, so you transmit on the printed frequency and listen on the VOR.
• T means transmit only.
• The FSS name under the box is who you are calling. Use it on the radio: "Princeton Radio, Skyhawk..."

The sectional is not the complete list. Other FSS frequencies may be usable depending on altitude and terrain, and the Chart Supplement has the full set. In Alaska, 121.5, 122.2 and 243.0 are available at many FSSs and are not printed above the boxes.

The specialist is a certified Pilot Weather Briefer but is not authorized to make original forecasts. They translate and interpret available weather into what to expect at departure, en route and destination. The briefing is complete when you have a clear picture, so ask about anything you do not follow.

• Notices to Airmen are time-sensitive notices issued by aviation authorities to alert pilots of essential information, hazards, or changes that could affect flight safety.
• Examples include runway or taxiway closures, NAVAIDs out of service, obstacles, temporary flight restrictions (TFRs), and parachute jumping.

The FAA NOTAM Search, as well as EFB apps such as ForeFlight

Yes, under part 91, with no formal operational approval, if you follow AC 91-78A. Using an EFB in flight in place of paper is the decision of the operator and the PIC.

The EFB may replace paper when:

• It does not replace any system or equipment part 91 requires, such as a navigation, communication or surveillance system.
• It shows only information functionally equivalent to the paper it replaces.
• The charts and data used for navigation or performance planning are current, up to date and valid, as verified by the pilot.
• It complies with § 91.21 and does not interfere with equipment required for flight.

Risks:

• System failure or shutdown in flight.
• Workload: inputs become more demanding in flight. Cross-check data entry and computed results.
• Display and lighting: at night, set its brightness so it does not impair night vision.
• An unsecured device: stow or secure it for takeoff and landing.
• Datalink weather on it is not live. Check the product time, since latency may limit how you can use it.

• Pilotage is navigation by reference to landmarks or checkpoints. It works on any course with adequate checkpoints.
• Dead reckoning is navigation solely by computation from time, airspeed, distance and direction, adjusted for wind to produce a heading and a groundspeed.

They are used together. Dead reckoning gives you the heading to fly and the time to each checkpoint; pilotage confirms it and corrects it as the checkpoints come up. The PHAK's exception is flights over water, where there are no checkpoints to pilot by, so dead reckoning is not paired with pilotage. Radio navigation is still available.

Choosing checkpoints well is most of what makes pilotage work:

• Pick prominent features common to the area: roads, rivers, railroads, lakes, power lines.
• Prefer features that bracket the course on each side, which shows a drift before it becomes a position error.

Three corrections, each for one thing:

• True course measured off the chart, then apply the wind correction angle to get true heading. Wind from the right is added, from the left subtracted.
• Apply variation to get magnetic heading.
• Apply deviation from the compass correction card to get compass heading.

Which way to apply variation: "east is least, subtract. West is best, add."

The PHAK's worked example: a true course of 090 with a wind correction angle of 14° from the left gives a true heading of 076. Variation and then deviation are applied to that to reach the compass heading.

• Variation is the angle between true north and magnetic north, a property of where you are on the Earth. It is read off the chart from the isogonic lines, the broken magenta lines connecting points of equal variation.
• Deviation is the error in your airplane's compass caused by magnetic influences within the aircraft: electrical circuits, radios, lights, tools, the engine, magnetized metal parts. It is read off the compass correction card.

Deviation is different for each airplane, and it may vary by heading in the same airplane, which is why the card lists several headings.

The line connecting points of zero variation is the agonic line. Isogonic lines change slightly over time, which is one reason chart currency matters.

It solves for the two things you cannot read off a chart: the heading to fly and the groundspeed you will make.

The three sides of the triangle pair up like this:

• Air vector: true heading and true airspeed, where the airplane is pointed and how fast it moves through the air.
• Ground vector: true course and groundspeed, where it actually tracks and how fast it moves over the ground.
• Wind vector: wind direction and velocity.

True course, TAS and the wind are the knowns; true heading and groundspeed are what the triangle gives you. The PHAK's worked case is an 080° heading at 120 kt airspeed producing a 090° course at 110 kt groundspeed.

• Airspeed and wind are independent. The airplane does not feel the wind; a pilot in a 70 knot gale is unaware of it unless the ground is observed.
• A tailwind adds to groundspeed, a headwind subtracts. 120 knots TAS with a 20 knot tailwind is 140 over the ground, and 100 against it.
• A crosswind drifts you off course, so it requires a wind correction angle into the wind to hold the course line.

A direct crosswind still costs groundspeed. Crabbing leaves your airspeed vector off the course line, so only the remaining component advances you: 100 knots TAS with a direct 30 knot crosswind makes about 95 over the ground.

The same geometry means a round trip in steady wind always takes longer than in calm air.

A reference phase signal broadcasts in all directions, and a variable phase signal rotates 360°. Your VOR receiver compares the timing differences and determines a bearing.

• A constellation of satellites in medium Earth orbit, with enough satellites visible for the receiver to calculate position
• Each satellite sends a signal containing its position and the highly accurate time the signal was sent.
• Your GPS receiver uses those signals to calculate distance from each satellite, producing a sphere of possible positions.
• Additional satellite signals narrow the position solution and help correct receiver clock error.

It depends on the receiver. VFR use covers everything from a fully integrated IFR/VFR installation to a handheld, and some limits belong only to VFR-only receivers.

Any GPS used VFR:

• Database currency. No rule requires a current database for VFR, but do not use an outdated moving map in or near critical airspace. Verify waypoints against current charts or the Chart Supplement.
• Do not rely on it alone. Cross-check with pilotage, dead reckoning and other navigation, and distrust the GPS when they disagree.
• Program it on the ground. Load VFR waypoints before takeoff, exercise caution when programming routes once airborne, and keep your eyes outside.

VFR panel-mount and handheld receivers add:

• No RAIM alerting. They cannot warn you that satellites were lost or that the position is wrong. IFR equipment classes have RAIM or an equivalent.
• No accuracy standard. No design standard of accuracy or integrity applies to a VFR receiver.
• Antenna location. A suction-cup antenna inside the cabin rarely sees all the satellites, so you can lose the signal, and without RAIM you may get a wrong position with no warning.
• They are not authorized for IFR navigation or approaches.

Legacy:

• Terminal (T):
  • 1,000-12,000 ft - 25 NM
• Low (L):
  • 1,000-18,000 ft - 40 NM
• High (H):
  • 1,000-14,500 ft - 40 NM
  • 14,500-18,000 ft - 100 NM
  • 18,000-45,000 ft - 130 NM
  • 45,000-60,000 ft - 100 NM

Minimum Operational Network (MON):

• Low (VL):
  • 1,000-5,000 ft - 40 NM
  • 5,000-18,000 ft - 70 NM
• High (VH):
  • 1,000-5,000 ft - 40 NM
  • 5,000-14,500 ft - 70 NM
  • 14,500-18,000 ft - 100 NM
  • 18,000-45,000 ft - 130 NM
  • 45,000-60,000 ft - 100 NM

Yes, but you cannot plan your flight to count on it if using the VOR for navigation. Also, be very wary of loss of signal.

Basic radar service is available from every commissioned radar facility, to any VFR aircraft that can communicate with it and is within radar coverage:

• Safety alerts
• Traffic advisories
• Limited radar vectoring, workload permitting
• Sequencing where procedures or a letter of agreement exist

Traffic advisories tell you where to look, not that you are separated. The controller calls a target whose position and track may put it near you, so you can see and avoid it. ATC's surveillance radar gives no altitude on a target unless that aircraft has Mode C and the facility can display it.

Vectors do not relieve you of anything. Accepting radar navigational assistance is not authorization to violate a regulation, and in many cases the controller cannot tell whether their instruction will put you into instrument conditions. If a vector would take you into cloud, say so.

Where more is offered:

• TRSA: participating VFR aircraft are separated from IFR and other participating VFR aircraft by 500 ft vertical, visual separation, or target resolution. You must hold an assigned altitude, and ATC may assign one that does not conform to § 91.159.
• Class C: separation between VFR and IFR is standard, not optional.
• Class B: everyone is separated.

You still see and avoid. § 91.113(b) applies whatever service you are receiving.

• Mode A, also written Mode 3/A, replies with the four-digit code you set, which identifies you on radar.
• Mode C is Mode A with altitude reporting: pressure altitude in 100 ft increments, sent to the radar and to TCAS and ADS-B In users.
• Mode S can also report altitude, and carries the aircraft's unique ICAO aircraft address, also called its Mode S code.
• The Traffic Information Service (TIS) uplinks nearby traffic to the cockpit using the Mode S transponder.
• On the ground, you should have altitude reporting on any time you are on the airport movement area.
• IDENT only when ATC asks.
• "Stop altitude squawk" means turn off automatic altitude reporting. ATC uses it when the transmitted altitude may be wrong. An incorrect altimeter setting does not change what the transponder sends, but it does put you at the wrong true altitude.

It starts on the ground. Before any cross-country, check the charts for airports or suitable landing areas along or near the route, and for navaids you could use to divert.

In flight, precision is not the priority:

• If time permits, start the diversion over a prominent ground feature. In an emergency, turn toward the alternate promptly: finishing the plotting, measuring and computing first may only make the emergency worse.
• Measure the course with a straightedge against the compass rose around a VOR, or approximate it from a nearby radial or a paralleling airway. Plotting on the chart is rarely practical and seldom necessary, since an alternate is usually not far off course. The trap: a VOR radial or a printed airway is a magnetic heading outbound from the station, so to get the course to the station you may need its reciprocal.
• Use rules of thumb for time, speed and distance. Attention is already divided between flying, computing and scanning.
• Confirm the fuel on board covers the new leg plus reserve.
• Advise ATC or flight service, and amend or close the flight plan.

For the diversion altitude, consider cloud heights, winds, terrain and radio reception.

The PHAK's order, and the first step is not what most people guess:

• Climb, if a town or city cannot be seen, mindful of traffic and weather. Altitude increases radio and navigation reception range and radar coverage.
• Identify a landmark. Near a town it may be possible to read the name off a water tower.
• Plot a position from two or more navaids if you have a VOR or ADF, or read present position and the nearest airport off a GPS.
• Communicate with any available facility, using the frequencies shown on the sectional. A controller may offer radar vectors.
• Direction finding assistance is available from some facilities. The controller has you hold the transmit button down a few seconds and release, over several headings, which lets them plot you and vector you to a landing site.
• If the situation becomes threatening, transmit on 121.5 MHz and squawk 7700.

Getting lost is most dangerous when low on fuel, so work the list early rather than after the reserve is gone.

Shapes and purpose:

• B is individually tailored, a surface area plus two or more layers, the upside-down wedding cake. Every cleared aircraft receives separation services.
• C is usually a 5 NM radius surface area with a 10 NM outer circle from 1,200 ft to 4,000 ft above the field, at airports with a tower and radar approach control.
• D exists where there is an operating control tower, and is shaped to contain the instrument procedures.
• E is the controlled airspace that is none of the above, with floors commonly at 700 or 1,200 ft AGL and 14,500 ft MSL where nothing lower is designated.
• G is uncontrolled. ATC has no authority or responsibility there.

Equipment in E and G does not come from the class. A Mode C transponder and ADS-B Out are still required at and above 10,000 ft MSL (excluding airspace at and below 2,500 ft AGL), above a Class B or C ceiling up to 10,000 ft MSL, and inside the 30 NM Mode C veil from the surface to 10,000 ft MSL. Much of that airspace is E or G.

• An ATC clearance from the facility having jurisdiction, before entering. "Radar contact" is not a clearance. The words you need are "cleared into the Class B."
• A two-way radio capable of communicating with ATC on assigned frequencies.
• An operable Mode C transponder and ADS-B Out.
• At least a private pilot certificate. A student pilot may operate there with the § 61.94 or § 61.95 training and endorsement. The appendix D, section 4 restriction is narrower than it is often stated: at those airports no person may take off or land unless the PIC holds at least a private certificate. An endorsed student may still transit the Class B above them.

Speed below the Class B floor or in a VFR corridor through it is limited to 200 knots. Inside Class B the limit is the general 250 knots below 10,000 ft.

• § 91.130 requires you to establish two-way radio communications with the facility providing air traffic services prior to entering, and thereafter maintain them while in the airspace.
• Calling and getting no answer is not establishing communication. You stay out until the controller answers you with your tailnumber.
• The AIM is explicit that this is a low bar: "(callsign) standby" means communications have been established and you may enter. If workload prevents immediate service, the controller will instead tell you to remain outside.
• Mode C transponder and ADS-B Out.
• No specific certificate is required, and a student pilot needs no special endorsement.

No clearance is required, which is the difference from Class B. Once two-way communications and radar contact are established, ATC separates VFR aircraft from IFR aircraft within the Class C and the outer area, using visual separation or 500 ft vertical. It also sequences all VFR aircraft to the primary airport and gives traffic advisories and safety alerts between VFR aircraft.

Within 4 NM of the primary airport at or below 2,500 ft AGL, the speed limit is 200 knots unless otherwise authorized or required by ATC.

• Establish communication before entering and maintain it while in the airspace. As in Class C, "(callsign) standby" means communications have been established and you may enter; if the controller is too busy, they will tell you to remain outside.
• No specific certificate and no endorsement.
• Class D itself requires no transponder and no ADS-B. That is not the same as none being required where you are.
  • A Class D inside the 30 NM Mode C veil picks up both: the veil is § 91.215(b)(2) for the transponder and § 91.225(d)(2) for ADS-B, and both are keyed to the same appendix D, section 1 airports.
  • A Class D within 10 NM of an appendix D, section 2 airport picks up the transponder only. § 91.215(b)(5)(ii) names that ring; § 91.225(d) does not list it, so no ADS-B requirement follows from it.
  • Being beneath a Class B or C shelf picks up neither. Both regulations attach the requirement to the airspace above a B or C ceiling, not below its floor.
• At any airport with an operating control tower, you need a clearance to take off, to land, or to operate on a runway or taxiway.

Within 4 NM of the primary airport at or below 2,500 ft AGL, the speed limit is 200 knots unless otherwise authorized or required by ATC.

When the tower closes, the airspace reverts: either the Class E surface area rules, or Class E from 700 ft AGL with Class G below it.

The controlled airspace that is not Class A, B, C or D. Its purpose is to provide enough controlled airspace to safely control and separate aircraft during IFR operations.

Where the floor sits:

• 1,200 ft AGL in many areas, the common default.
• 700 ft AGL or the surface in many others, typically where there is an instrument approach.
• Some Class E begins at an MSL altitude depicted on the chart.

How a sectional shows it, per the Chart Users' Guide:

• A magenta vignette marks a floor of 700 ft AGL.
• A blue vignette marks a floor other than 700 ft that laterally abuts Class G.
• A magenta dashed line marks Class E surface airspace.

Class E extends up to but not including 18,000 ft MSL, and all airspace above FL600 is also Class E.

No clearance and no communication are required to fly VFR in it, and the weather minimum steps to 5 SM at and above 10,000 ft MSL.

A Mode C transponder and ADS-B Out can still be required in Class E, but the requirement comes from where you are, not from the class: above 10,000 ft MSL, above a Class B or C ceiling, or inside the Mode C veil.

Uncontrolled airspace: the portion not designated Class A, B, C, D or E. It runs from the surface up to the base of the overlying Class E, so the top is wherever Class E starts.

Working upward, that base is:

• 700 ft AGL, shown by a magenta vignette, typically around an airport with an instrument approach.
• 1,200 ft AGL in many areas, the common default.
• 14,500 ft MSL where no lower Class E floor is designated. Note MSL, not AGL.

Above 14,500 ft MSL it is Class E, with one exception: airspace less than 1,500 ft above the terrain stays Class G. Over 14,000 ft terrain in the mountain west, Class G continues above 14,500 ft MSL.

ATC has no authority or responsibility to control traffic in Class G, and nothing is required to enter: no clearance, no equipment, no communication. The VFR weather minimums still apply, and they are the most complex in the § 91.155 table because they split by altitude and by day or night.

The § 91.155 table, for aircraft other than helicopters. 152 is shorthand for 500 ft below, 1,000 ft above, 2,000 ft horizontal.

One pattern makes the table easier to hold: at and above 10,000 ft MSL the clearances change shape to 1,000 above, 1,000 below and a full statute mile horizontally.

A narrow exception: at night in Class G below 1,200 ft AGL, within half a mile of the runway in an airport traffic pattern, an airplane may operate clear of clouds with at least 1 SM.

Two more rules in the same section, and neither is in the table:

• § 91.155(c): you may not operate beneath the ceiling under VFR inside the lateral boundaries of controlled airspace designated to the surface for an airport when the ceiling is less than 1,000 ft.
• § 91.155(d): you may not take off, land, or enter the traffic pattern under VFR within the surface areas of Class B, C, D or E unless ground visibility at that airport is at least 3 SM, or, where ground visibility is not reported, flight visibility is at least 3 SM.

Both are excepted by special VFR.

Because everyone in Class B is separated by ATC. A clearance is required for all aircraft, and the PHAK states that all aircraft that are so cleared receive separation services within the airspace.

• The regulation gives no reason, but the usual reading follows from that: with no unknown traffic to see and avoid, the cloud clearance need only keep you out of the cloud itself, so clear of clouds is enough.
• In Class C and D, VFR traffic is not separated from other VFR traffic. You remain responsible for seeing and avoiding, so the 500 below, 1,000 above and 2,000 horizontal buys the distance to spot an airplane emerging from a cloud.

What it is

Special VFR (SVFR) is an ATC clearance that allows a VFR aircraft to operate within controlled airspace designated to the surface for an airport when the weather is below basic VFR minimums. For airplanes, SVFR generally requires at least 1 statute mile visibility and clear of clouds.

When you'd use it

You might use SVFR to enter, leave, or operate within a surface area when the weather is below normal VFR minimums, but conditions are still good enough to safely remain clear of clouds with the required visibility. For example, an airport might have a low cloud layer that makes the field technically IFR, while visibility below the layer is adequate for a short VFR departure or arrival.

How to request it

To request it, you can call tower and say "Tower, Archer 3096B, request Special VFR departure to the west".

Rules to follow

For airplanes, you need at least 1 SM visibility and must remain clear of clouds. At night, the pilot must be instrument rated and the airplane must be IFR equipped. SVFR is traffic permitting, applies only within the surface area, and is prohibited for fixed-wing aircraft at certain airports.

They apply in level cruising flight more than 3,000 ft above the surface, except while holding in a pattern of 2 minutes or less, while turning, or where otherwise authorized by ATC. Below 18,000 ft MSL:

• Magnetic course 0° through 179°: odd thousands plus 500. 3,500, 5,500, 7,500.
• Magnetic course 180° through 359°: even thousands plus 500. 4,500, 6,500, 8,500.

Course, not heading. A wind correction does not change which rule applies.

At or below 3,000 ft AGL the rule does not bind, so you may cruise at any altitude subject to § 91.119. The ATC exception is not academic either: controllers routinely assign VFR altitudes that do not conform to § 91.159 on a Class B transition.

From § 91.119, except when necessary for takeoff or landing:

• Anywhere: an altitude allowing an emergency landing without undue hazard to persons or property if a power unit fails.
• Over congested areas of a city, town or settlement, or an open air assembly: 1,000 ft above the highest obstacle within a horizontal radius of 2,000 ft of the aircraft.
• Other than congested areas: 500 ft AGL.
• Over open water or sparsely populated areas: no altitude floor, but you may not operate closer than 500 ft to any person, vessel, vehicle or structure.

The "anywhere" rule binds on top of the others, not instead of them. Meeting the 500 ft figure in paragraph (c) is no defense if a power failure at that altitude and over that ground would put the airplane into something, because paragraph (a) is about undue hazard to persons or property on the surface.

Three limits from § 91.117:

• 250 knots indicated below 10,000 ft MSL, unless otherwise authorized by the Administrator.
• 200 knots at or below 2,500 ft above the surface within 4 NM of the primary airport of Class C or Class D airspace, unless otherwise authorized or required by ATC. Controllers do assign speeds there.
• 200 knots in the airspace underlying Class B, or in a VFR corridor through it, on the same ATC exception.

The 200 knot limit does not apply inside Class B itself. There you comply with the 250 knot rule.

If the minimum safe airspeed for any particular operation is greater than the limit, you may fly at that minimum speed.

The duty to see and avoid comes first. § 91.113(b): when weather permits, vigilance to see and avoid other aircraft is maintained whether you are IFR or VFR. Where a rule gives another aircraft the right of way, you give way and may not pass over, under or ahead of it unless well clear.

• In distress: right of way over all other air traffic.
• Converging, same category and about the same altitude: the aircraft to the other's right has the right of way.
• Head-on or nearly so: each pilot alters course to the right. Nobody has the right of way.
• Overtaking: the aircraft being overtaken has it. The overtaking aircraft alters course to the right to pass well clear.
• Landing: aircraft on final approach or landing have it over aircraft in flight or on the surface. With two or more approaching to land, the lower aircraft has it.

Converging aircraft of different categories run least maneuverable first:

Balloon, then glider, then airship, then powered parachute, weight-shift-control, airplane and rotorcraft. An aircraft towing or refueling another has the right of way over all other engine-driven aircraft.

Two anti-abuse clauses sit in the rule itself. A landing aircraft may not use its priority to force an aircraft that has already landed off the runway, and a lower aircraft on approach may not use its priority to cut in front of or overtake another on final.

Air Defense Sectors monitor traffic with the FAA and can order an intercept in the interest of national security. An interceptor may be trying to identify, track, inspect, divert or establish communications with your aircraft.

Before it happens: maintain a listening watch on the guard frequencies, 121.5 or 243.0 MHz. All aircraft in U.S. national airspace are highly encouraged to, and if you are intercepted it is on you to establish contact.

How it unfolds. Interceptors approach from behind, usually in pairs though sometimes singly, then close to a distance sufficient for positive identification.

The ICAO signals, which are the part to know cold:

If you cannot keep pace, the interceptor is expected to fly race-track patterns, rocking its wings each time it passes you.

Terrain or weather may put the interceptor on your right instead, with the turn to the right.

• Prohibited area - Flight is prohibited, period. Established for security or national welfare reasons, e.g., P-56 over the White House.
• Restricted area - Hazardous activity such as artillery fire, gunnery, or missile testing. You need permission from the controlling agency unless it's inactive and released.
• Warning area - The same kind of activity as a restricted area, but starting 3 NM off the coast over domestic or international waters. It's advisory in nature, because the airspace can't be prohibited.
• Military Operations Area (MOA) - Separates military training from IFR traffic. VFR traffic isn't prohibited, but exercise real caution.
• Alert area - High volume of pilot training or unusual aerial activity. Everybody in there is equally responsible for seeing and avoiding.
• Controlled firing area - Activity stops when an aircraft approaches, which is why these aren't charted.
• National security area - Flight avoidance is requested, and can be made mandatory by NOTAM.

• Pressure altitude is the height above the standard datum plane, the theoretical level where pressure is 29.92 inHg and air weighs 14.7 psi. Set the altimeter to 29.92 and what it reads is pressure altitude.
• Density altitude is pressure altitude corrected for nonstandard temperature. It is the altitude in the standard atmosphere corresponding to the actual air density.

Density altitude is the one that governs performance, because the airplane responds to air density, not to elevation:

• Lower density altitude means denser air and better performance.
• Higher density altitude means thinner air and worse performance.

Conditions producing a high density altitude: high elevation, low atmospheric pressure, high temperature, high humidity, or any combination. The reverse gives a low density altitude.

Takeoff distance is set by the lift-off speed and the rate of acceleration to it, so anything changing either one changes the distance. The PHAK's figures show how badly it scales.

Weight has a threefold effect: a higher lift-off speed, a greater mass to accelerate, and more retarding force from drag and ground friction. A 10% increase in gross weight gives:

• A 5% increase in takeoff velocity
• At least a 9% decrease in rate of acceleration
• At least a 21% increase in takeoff distance

Wind, and note the asymmetry:

• A headwind of 10% of takeoff airspeed reduces the distance about 19%.
• A tailwind of 10% increases it about 21%.
• A headwind of 50% of takeoff speed cuts the distance to about 25% of the zero-wind figure.

The effect of wind on landing distance is identical.

Density altitude drives both. Pressure altitude and temperature together define it, and it is the first of the four inputs the PHAK uses to predict either distance: density altitude, gross weight, wind, and runway slope and condition. Landing distance alone grows about 3.5% for each 1,000 ft of altitude.

So a tailwind hurts more than the same headwind helps. The weight penalty differs by phase: on takeoff it is roughly double the percentage you added, while landing distance varies in direct proportion to gross weight, so 10% more weight is about 10% more landing distance. Neither is intuitive, and both are the margin you thought you had.

Off the chart in the POH. Take the angle between the runway heading and the wind direction, follow that radial out to the arc for the wind speed, then from that intersection draw a line straight down for the crosswind component and straight across for the headwind component.

Worked the PHAK's way: runway 17, wind 140 at 25 kt. Runway 17 points 170°, the wind is from 140°, so the wind angle is 30°. Follow the 30° line to the 25 kt arc: the crosswind component is 13 kt and the headwind component is 22 kt.

The arithmetic behind the chart is just the angle: crosswind is the wind speed times the sine of the wind angle, so 30° is half of it. That gives 12.5 kt here, close enough to confirm you read the chart correctly, but the chart is the answer.

Maximum demonstrated crosswind component is what a pilot of average skill achieved in a 90° crosswind during certification, tested at velocities up to 0.2 V_S0. An airplane stalling at 45 kt must be capable of landing in a 9 kt 90° crosswind. Your airplane's figure is in the AFM/POH.

It records what was demonstrated, not a structural limit. The AFH still lists exceeding it as a common error, and your own limit on the day may be lower than the book's.

Start with induced drag. A lifting wing has higher pressure underneath than on top, so air spills around the tips from below to above. That rolling flow becomes the wingtip vortices, which angle the air downward behind the wing. That downwash is the wing doing the work of making lift, and induced drag is the price of it.

Within about a wingspan of the surface, the ground gets in the way of that downward flow. The vortices cannot fully develop, there is less downwash, and so there is less induced drag.

What you feel:

• The wing makes the same lift at a lower angle of attack, which is the floating in the flare.
• Induced drag dominates at low speed, so thrust required drops noticeably down low.

The takeoff trap: you can lift off below normal flying speed, climb out of ground effect, meet the full induced drag again and settle back onto the runway. Ground effect also raises the pressure at the static port, so the airspeed and altimeter read low while it happens.

Both are climb speeds. They answer different questions.

Why they differ. Angle of climb comes from excess thrust, and in a propeller airplane the maximum occurs at a speed below L/D_MAX, frequently just above stall. Rate of climb comes from excess power, which peaks at a higher speed. So V_X is the slower of the two.

Maximum rate is not always enough. Max ROC may fail to clear an obstacle that max AOC would clear, which is the entire reason both exist.

On a normal takeoff the airplane is pitched to accelerate to V_Y, and takeoff power is held to at least 500 ft above the surrounding terrain or obstacles. That combination gives the most altitude in the least time, which is altitude you can maneuver from if the engine quits.

On a short field you climb at V_X until the obstacle is cleared, then lower the nose to V_Y and retract flaps.

One caution: V_Y is slow enough that an engine failure demands quick response to avoid a stall, so a cruise climb at a lower pitch is often the better choice once clear.

Normal command is the intuition you build in cruise: holding altitude, a higher airspeed needs more power and a lower airspeed needs less. Most flying, climb, cruise and maneuvering, happens here.

Reversed command is the opposite relationship: holding altitude, a higher airspeed needs less power and a lower airspeed needs more. It covers the speeds between the best endurance speed, the lowest point on the power required curve, and the stall.

Why it flips. The power required curve is U-shaped. Below its lowest point, slowing down increases the power needed to hold altitude, because induced drag is climbing faster than parasite drag is falling. Needing more power as you slow is contrary to normal command, which is where the name comes from.

Be precise about what it does not mean. It does not mean a power reduction produces a lower airspeed. It is a statement about the power required to hold altitude at a given speed.

Why the controls appear to swap. Down here you have little excess power, so the throttle is what buys or costs you altitude, and pitch is what sets the speed. Two cases make it concrete:

• A low-airspeed, high-pitch power approach to a short field. If an unacceptable sink rate develops, power may reduce or stop it. Lowering the nose alone, without power, gives a rapid sink rate and loss of altitude, and without power the airplane would probably stall or be unable to flare.
• A soft-field climb out of ground effect before reaching normal climb pitch and airspeed. The airplane can enter the region at a dangerously low altitude where even full power will not climb or hold altitude, and the only recourse is to lower the nose and accept the altitude loss.

Hence the emphasis on precise airspeed control at low speeds.

V_A is the maximum speed at which the positive design load limit can be imposed, either by a gust or by full one-sided deflection of one control surface, without causing structural damage.

Operating at or below V_A does not protect against multiple full control inputs in one axis, or full control inputs in more than one axis at the same time.

At or below V_A the airplane reaches the critical angle of attack first, and the stall unloads the wing before the load limit is exceeded. Above V_A it reaches the load limit at less than the critical AOA, so no stall intervenes.

V_A decreases as weight decreases. A lighter airplane stalls at a lower speed, so the protective stall has to arrive sooner.

Some airplanes publish V_O instead, a historical operating limitation applicable to certain airplanes only: the maximum speed where, at any given weight, you may apply full control excursion without exceeding the design limit load factor.

Load factor is the ratio of the load the wing carries to the weight of the airplane. In a level turn it is the vector sum of gravity and centrifugal force, so it depends only on bank angle, not on weight or airspeed.

Stall speed increases in proportion to the square root of the load factor, which is where the third column comes from. The curve is nearly flat to 45° and then climbs steeply. Going from 60° to 80° costs far more than going from 0° to 60°.

Certificated limit load factors:

• Normal: 3.8 to -1.52
• Utility, mild acrobatics including spins: 4.4 to -1.76
• Acrobatic: 6.0 to -3.0

A 50 percent safety factor is added to those limits, and the normal-category limit is reduced for aircraft over 4,000 lb gross.

Stall speed rises because holding altitude in a bank needs a higher AOA. Let the AOA go excessive at any point in the turn and the airplane stalls, well above the wings-level speed.

Most airplanes are designed with the wing's center of lift behind the CG, which makes them nose heavy, so the horizontal stabilizer carries a downward force that holds the tail down and keeps the nose from pitching down. It is a lever: lift up at the CL, weight down at the CG ahead of it, a smaller download at the tail behind it.

Moving the CG forward lengthens the weight's arm, so the tail must push down harder to balance it. The wing now has to support weight plus that tail download, which is why a forward CG behaves like a heavier airplane:

• Higher stall speed, because more lift is needed
• More induced drag, so slower cruise
• Higher control forces, and eventually not enough elevator to flare

Moving the CG aft shortens that arm, so less download is needed, the wing carries less, and the airplane cruises faster. You pay in stability. Tail heavy loading reduces longitudinal stability and the ability to recover from stalls and spins, and makes control forces very light, so it is easy to overstress the airplane. Aft of the allowable range it can mean extreme control difficulty and violent stall characteristics.

Overweight is the separate limit. It compromises structural integrity and adversely affects performance, and the stability of many certificated airplanes is completely unsatisfactory above gross weight.

Baggage counts too. Unsecured or improperly loaded baggage can move the CG, which is why the pilot supervises loading and securing it.

Shifting weight leaves the total weight unchanged and changes only the moments, so one proportion solves it:

weight shifted ÷ total weight = change in CG ÷ distance the weight is moved

• Moving weight aft increases total moment and moves the CG aft. Moving it forward does the opposite.
• Solve for the weight to move when you know the CG change you need, or for the CG change when you know the weight.

The PHAK's example: a 7,800 lb airplane has its CG at 81.5 in, with an aft limit of 80.5 in. Cargo moves from the aft compartment at station 150 to the forward one at station 30, a distance of 120 in, and the CG must move 1.0 in:

• weight to move = 7,800 lb × 1.0 in ÷ 120 in = 65 lb

Moving 65 lb puts the CG exactly at the aft limit.

Four separate strokes of the piston convert chemical energy into mechanical energy, in this order:

• Intake. The piston starts down, the intake valve opens, and the fuel-air mixture is drawn into the cylinder.
• Compression. The intake valve closes and the piston moves back up, compressing the mixture to get far more power out of it once ignited.
• Power. The mixture is ignited, pressure rises sharply, and the piston is forced down. This is the only stroke producing power.
• Exhaust. The exhaust valve opens and the rising piston purges the burned gases.

Even at fairly low engine speed the full cycle happens several hundred times each minute in every cylinder.

Only one stroke in four produces power, so the other three are driven by the crankshaft's momentum and by the other cylinders. Each cylinder is on a different stroke, and continuous rotation depends on the precise timing of the power strokes, which is why losing a cylinder costs smoothness as well as power.

Two magnetos, separate wires, and two spark plugs in each cylinder. Each magneto fires one plug per cylinder and operates independently, for two reasons:

• Redundancy. If a magneto or a plug fails, the engine runs normally with a slight power decrease.
• Performance. Two plugs improve combustion and give slightly higher power output, so it is not purely a backup.

The mag check. Switch arrangements vary, the check does not: running on both, isolate one magneto, note the indications, return to both to recover, then isolate the other.

• A small RPM drop is normal. With one plug firing instead of two, a single flame front has to cross the whole chamber, so the mixture burns more slowly.
• EGT rises, for the same reason. The slower burn is still finishing later in the cycle, so hotter gas reaches the exhaust valve.
• No drop at all is a finding. It suggests a magneto is not being grounded by the switch, meaning the engine can fire with the ignition off.
• The permissible drop is in the AFM or POH, not a universal number.
• If the engine quits on one magneto, or a drop exceeds the limit, do not fly. Fouled plugs and broken or shorted wires are the usual causes.

Engines are calibrated at sea level pressure, where FULL RICH gives the correct ratio. As you climb, the density of the air entering the engine falls while the density of the fuel does not, so the mixture becomes progressively richer on its own. This applies to carbureted and fuel-injected engines alike.

An over-rich mixture gives engine roughness and an appreciable loss of power.

The roughness is fouled plugs, not the mixture itself: a rich mixture lowers the temperature inside the cylinder, which inhibits complete combustion, which leaves carbon building up on the spark plugs.

So leaning is not only about fuel economy. It protects the plugs and recovers power you lose by climbing.

Leaning too far has its own cost. An excessively lean mixture at high power is one of the PHAK's listed causes of detonation, along with rough running, overheating and power loss, so enrich for takeoff, climb and any high power setting.

The PHAK's guidance is to monitor engine temperature and enrich as needed, and it notes an EGT gauge gives better mixture control and fuel economy on fuel-injected engines. The specific procedure varies, so the AFM or POH governs.

Both are abnormal combustion, and they differ in when the mixture burns.

Detonation is an uncontrolled, explosive ignition of the mixture inside the cylinder. It is characterized by high cylinder head temperatures and is most likely at high power settings. Severe cases fail the piston, cylinder or valves; milder ones cause overheating, roughness or power loss.

Common causes:

• A fuel grade lower than the manufacturer specifies
• High manifold pressure with low RPM
• High power with an excessively lean mixture
• Extended ground operations or steep climbs, where cylinder cooling is reduced

Preignition is the mixture igniting before the normal ignition event, usually from a hot spot in the combustion chamber: a carbon deposit on a plug, a cracked plug insulator, or other damage heating a part enough to light the charge. It also causes power loss and high operating temperature, and it damages the engine the same way detonation does: the expanding gases exert excessive pressure on the piston while it is still on its compression stroke.

You often cannot tell the two apart in the airplane. They frequently occur simultaneously and one may cause the other, and since both produce high engine temperature with a loss of performance, distinguishing them in flight is often not possible.

Avoiding detonation is mostly cooling and mixture discipline: correct fuel grade, cowl flaps, if fitted, open on the ground, an enriched mixture and a shallow climb angle during takeoff and initial climb, and monitoring the engine instruments.

Fuel vaporizing and air pressure dropping in the venturi both cool the carburetor sharply: a temperature drop of as much as 60 to 70 °F. If water vapor condenses while the carburetor is at or below freezing, ice forms at the throttle valve and venturi throat, restricting fuel-air flow and reducing power. Enough of it stops the engine.

When to expect it:

• Most likely below 70 °F (21 °C) with relative humidity above 80%.
• But possible in outside air as warm as 100 °F (38 °C) and humidity as low as 50%, because of the size of that temperature drop.

How you notice it depends on the propeller:

• Fixed-pitch: a decrease in RPM, possibly followed by engine roughness.
• Constant-speed: a decrease in manifold pressure with no RPM change, because the governor adjusts pitch to compensate.

Carburetor heat is also the test. Apply it and watch the same gauge: if ice is present the indication drops further and then gradually recovers as the ice melts. If it drops and simply holds steady, there was no ice.

It is most dangerous at reduced power in a descent, where ice can build unnoticed until you add power and find it.

If you find it, use full heat. Partial heat, or heat left on for too short a time, can make the situation worse. Expect a further power loss and rough running for 30 seconds to several minutes as melted ice passes through the engine, and leave the heat full hot until normal power returns. It costs up to 15% power and enriches the mixture, so it is not used when full power is required. Prevention is the better use of it, and it doubles as an alternate air source if the intake filter clogs.

A fuel injection system delivers fuel directly into the cylinders or just ahead of the intake valve, rather than mixing it in a venturi upstream.

Advantages:

• Reduction in evaporative icing, since there is no venturi temperature drop to freeze
• Better fuel flow and better fuel distribution between cylinders
• Faster throttle response
• Precise control of mixture
• Easier cold weather starts

Disadvantages:

• Difficulty starting a hot engine
• Vapor lock during ground operations on hot days
• Problems restarting an engine that quit from fuel starvation

Note what is not on the advantage list: impact icing is still possible. Ice forming on the outside of the aircraft can block the air intake on either system, which is why an injected airplane still has an alternate air source, usually automatic with a manual backup.

So injection makes an engine less susceptible to carburetor icing. It does not remove induction icing.

The system has to deliver clean fuel to the engine under all conditions of power, altitude and attitude, and in every approved maneuver.

Gravity feed. On a high-wing airplane the tanks sit in the wings, above the engine, so gravity alone moves the fuel. No pump is required.

Fuel pump system. On a low-wing airplane the wing tanks sit below the engine, so gravity cannot do it. These aircraft carry two pumps:

• An engine-driven main pump
• An electrically driven auxiliary, also called the boost pump, controlled from the flight deck

The auxiliary exists for starting and in the event the engine pump fails. That is the redundancy, and it is the reason the boost pump appears on checklists for takeoff and landing on low-wing types: those are the phases where an engine pump failure leaves you least time.

A fuel primer is fitted to both kinds of system, drawing fuel and delivering it directly to the cylinders for starting.

Oil does five jobs, and only one of them is lubrication:

• Lubricates the engine's moving parts
• Cools the engine by reducing friction
• Removes heat from the cylinders
• Seals between the cylinder walls and pistons
• Carries away contaminants

A significant share of engine cooling runs through the oil, which is why oil temperature is an engine health indication and not just a lubrication check.

Wet sump: the oil sits in a sump that is an integral part of the engine. This is what most training airplanes use.

Dry sump: the oil is held in a separate tank and circulated through the engine by pumps.

The main component of a wet-sump system is the oil pump, which draws oil from the sump and routes it through the engine, then through a filter and cooler before returning.

Most aircraft run a 14 or 28 volt DC system. The components:

• Alternator or generator, engine driven
• Battery
• Master/battery switch and alternator switch
• Bus bar, fuses and circuit breakers
• Voltage regulator
• Ammeter or loadmeter
• The associated wiring

The alternator supplies current to the system and maintains the battery's charge. The battery starts the engine and provides a limited supply if the alternator fails.

That word limited is what the system comes down to for a pilot. Once the alternator quits, everything is running off a battery with a finite endurance, so the response is to shed load and land.

An ammeter shows current flowing to or from the battery: a positive reading means it is charging, a negative reading means the battery is carrying the load and the alternator is not. A loadmeter instead shows the total load being drawn from the alternator.

The two full-scale readings are each a specific failure. Full-scale minus indicates a malfunction of the alternator or generator; full-scale positive indicates a malfunction of the voltage regulator. Either way the AFM/POH has the action. Not every airplane has an ammeter: some use a warning light that illuminates to show a discharge.

It is engine driven, usually by a belt, so it spins whenever the engine runs.

Making the electricity. The spinning rotor is an electromagnet, not a permanent magnet. A small field current through its windings is what makes it a magnet. Spinning that magnet past the stationary windings induces alternating current, and diodes inside the alternator rectify it to DC.

Where the field current comes from. The battery and bus, through the alternator field circuit: whatever switch the airplane uses to control the alternator, plus its circuit breaker. Arrangements vary between types. The voltage regulator sets output by varying it: more field current, stronger magnet, more output. Output is held above battery voltage so the battery charges, roughly 14 volts for a 12 volt battery.

Turning it off. The switch cannot stop the alternator turning, because the belt is still driving it off a running engine. It removes the field current, so the rotor stops being a magnet and there is nothing to induce against. The alternator keeps spinning and produces nothing.

That is how you isolate a failed or overvoltage alternator in flight. The entire load is then on the battery, so shed everything nonessential.

The ailerons, the elevator or stabilator, and the rudder. Each changes the airflow and pressure over its surface, which changes lift and drag and moves the airplane about one axis.

• Adverse yaw: the down aileron makes more lift and more drag, so the airplane yaws away from the turn. Rudder counters it. It takes the most rudder at low airspeed, high angle of attack and large aileron deflections.
• A stabilator is a one-piece horizontal tail that pivots as a unit. It is very sensitive, so an antiservo tab that moves in the same direction adds control force and trims it.
• Controls feel soft and sluggish at low airspeed and firmer, with faster response, at high airspeed. Rudder effectiveness rises with speed and with propeller slipstream over the tail.
• Design limits such as control stops keep you from overcontrolling and overstressing the airplane in normal maneuvering.

Flaps are trailing-edge high-lift devices that increase both lift and induced drag at any given angle of attack. They let you land slowly while still cruising fast.

Fully extended, plain and split flaps produce high drag with little additional lift, so the last notch steepens the approach rather than adding lift.

A Fowler's first portion of travel increases drag very little but lift a great deal, adding area and camber. As extension continues it deflects downward and the drag arrives.

Flap extension may cause a nose-up or nose-down pitching moment depending on the type, which you compensate for, usually with trim.

Gear with the third wheel at the nose is tricycle; with it at the rear it is conventional, or tailwheel.

The PHAK gives three advantages for tricycle gear:

• It allows more forceful braking during high-speed landings without nosing over.
• It gives better forward visibility during takeoff, landing and taxi.
• It tends to prevent ground looping, because the CG is forward of the main wheels, which keeps the airplane moving in a straight line rather than swerving.

Brakes are on the main wheels only, applied by hand control or by foot pedals, toe or heel.

Foot pedals operate independently, which gives differential braking: braking one main wheel more than the other to help turn. On the ground this supplements nosewheel or tailwheel steering, and it is what lets you make a tight turn or hold a crosswind-affected taxi line.

Nosewheels are either steerable, linked to the rudders by cables or rods, or castering, free to swivel. A castering nosewheel is steered entirely by differential braking.

A constant-speed propeller holds a selected RPM by changing blade angle, so the engine stays at the RPM you set as airspeed and power change. The propeller governor is what does the work.

• Inside the governor, engine-driven flyweights are opposed by an adjustable speeder spring. The propeller control changes spring tension, which is how you select an RPM.
• The flyweights position a pilot valve that meters engine oil to or from a piston in the propeller hub.
• On speed - Flyweights and spring balanced, pilot valve centered, blade angle steady.
• Overspeed - RPM above the setting, flyweights move out, the governor increases blade angle (coarser) to add load and slow the engine back down.
• Underspeed - RPM below the setting, flyweights move in, the governor decreases blade angle (finer) to unload the engine so it accelerates.

Which way oil moves the blades

• On almost all single-engine airplanes, the propeller is oil-pressure-to-increase-pitch: governor oil drives the blades toward high pitch / low RPM, and a spring plus the blades' natural centrifugal twisting moment drives them back toward low pitch / high RPM.
• The consequence is the failure mode: lose governor oil pressure in a single and the propeller goes to low pitch, high RPM - the setting that gives you full power for a go-around. You may see the engine overspeed in a descent, but you are not left without thrust.
• Most light twins use the opposite arrangement, oil-pressure-to-decrease-pitch with counterweights, so a loss of oil pressure moves the propeller toward feather. That reversal is deliberate: on a twin, a failed engine that drifts toward feather beats one windmilling flat at maximum drag.

Flying it

• Throttle controls manifold pressure, propeller control sets RPM. Read manifold pressure on the MP gauge and RPM on the tachometer.
• Increasing power, go prop forward then throttle up. Reducing power, go throttle back then prop back. The point is to avoid unapproved high-manifold-pressure/low-RPM combinations - such settings are fine when the AFM/POH power charts specifically approve them.
• At low blade angles the governor may hit its low-pitch stop, and below that the propeller behaves like a fixed-pitch one - which is why RPM rises with airspeed on takeoff roll and in a dive at full-forward prop.
• A controllable-pitch propeller is one of the three items in the complex definition under § 61.31(e), along with retractable gear and flaps.

Four effects of a propeller turning clockwise as seen from the pilot's seat, as on most U.S. engines. Together they are what pilots call "torque."

• Manufacturers set the compensation for torque at cruise. Aileron trim tabs adjust for other speeds, and on the ground you hold the left yaw with rudder.
• Which element dominates changes with the phase of flight and with the airframe, engine and propeller combination.

The system combines static pressure with the dynamic pressure of the aircraft moving through the air, and drives three instruments:

That split explains the failure consequences. A blocked pitot tube affects only the airspeed indicator. A blocked static port affects all three, because two of them have no other source.

On preflight, confirm the pitot cover is removed and check both the pitot and static openings. Blockages come from moisture and ice, dirt, or insects, which is why a tube left uncovered on the ramp is a real risk rather than a theoretical one.

Some airplanes have an alternate static source, normally inside the flight deck. The venturi effect of air flowing around the fuselage makes flight deck pressure lower than outside, so selecting it gives:

• The altimeter a slightly higher altitude than actual
• The airspeed indicator an airspeed greater than actual
• The VSI a momentary climb, then it stabilizes if altitude is held

Three cases, each behaving differently.

Pitot blocked, drain hole clear. Ram air cannot enter and the air already in the system vents out the drain, dropping to ambient pressure. The airspeed indicator senses no difference between ram and static, so airspeed falls to zero. Not quite instantly, but very quickly.

Pitot opening and drain hole both blocked. Pressure is trapped. The airspeed indicator does not respond to actual speed changes at all, but it does respond to altitude changes, behaving like an altimeter: climb and it reads higher, descend and it reads lower.

Static blocked, pitot clear. The airspeed indicator keeps working but is inaccurate, because the trapped static pressure is only correct for the altitude where the blockage occurred:

• Above that altitude, the trapped pressure is too high, so the airspeed indicator reads lower than actual.
• Below it, the trapped pressure is too low, so the airspeed indicator reads higher than actual.

A blocked static also freezes the altimeter and flatlines the VSI.

What you do about it:

• Pitot heat, where fitted, for flight in visible moisture. The AFM/POH gives the procedure.
• For a blocked static, open the alternate static source if the airplane has one. It draws from the flight deck, where pressure is lower than outside, so the altimeter reads slightly high, the airspeed indicator reads high, and the VSI shows a momentary climb before settling. The AFM/POH gives the corrections.
• With no alternate source fitted, break the glass face of the VSI. It is the least important of the three static instruments, and breaking it lets flight deck pressure into the system.

Three: the attitude indicator, the heading indicator, and the turn coordinator.

They rely on two properties of a spinning rotor:

• Rigidity in space: a gyro stays fixed relative to space unless an outside force acts on it. This is what the attitude and heading indicators use as their reference.
• Precession: a force applied to a spinning gyro takes effect 90° later in the direction of rotation. This is what makes the turn coordinator work.

Power comes from two sources, and the split is deliberate:

• Vacuum or pressure driven, typically the attitude indicator and heading indicator
• Electrically driven, typically the turn coordinator

Splitting them is the redundancy. A vacuum pump failure takes the attitude and heading indicators but leaves the electric turn coordinator, so you still have a bank reference. That is why the turn coordinator is the instrument to trust after a vacuum failure, and why identifying which of your instruments is on which source is a preflight question rather than an inflight one.

• ANDS (Accelerate North, Decelerate South): On east/west headings, acceleration causes a false turn toward north and deceleration toward south because the compass is weighted on its south-seeking end to counter magnetic dip. Inertia makes that weighted end lag or swing forward, rotating the compass card.
• UNOS (Undershoot North, Overshoot South): When turning toward north, the compass lags, so undershoot north. When turning toward south, it leads, so overshoot south. This happens because the compass hangs pendulously below its pivot, and banking lets magnetic dip tilt and rotate the compass assembly, producing the turning error.

Required on FAA-certificated aircraft of 12,500 lb or less manufactured after 1945, so you can read a limitation at a glance.

The two stall speeds are the ones to keep apart. V_S0 is measured in the landing configuration, gear and flaps down, at maximum landing weight. V_S1 is clean, gear and flaps up, at maximum takeoff weight. Both are power-off.

Not every limitation is on the dial. V_A, V_LE and V_LO among others appear only on placards and in the AFM/POH, because they change with weight or configuration and a fixed marking cannot show that.

If the needle is in the yellow arc and moving toward the red line, the response is to reduce airspeed.

• Hypoxic - Not enough oxygen pressure available for oxygen to cross into the bloodstream. This is the altitude type.
• Hypemic - The blood can't carry the oxygen. Carbon monoxide poisoning, anemia, blood loss, or a recent blood donation.
• Stagnant - The blood isn't moving well. Heart problems, G loading, or cold restricting circulation to the extremities.
• Histotoxic - The cells can't use the oxygen they're given. Alcohol or drugs.

Symptoms to catch early include euphoria or belligerence, degraded judgment, headache, tunnel vision, and cyanosis in the fingernails and lips. Night vision starts degrading as low as 5,000 ft, and performance can seriously deteriorate within 15 minutes at 15,000 ft. The fix is oxygen and a descent. Since the symptoms overlap with hyperventilation, treat for hypoxia first when you're not sure.

• Hyperventilation is blowing off too much carbon dioxide by breathing too fast, usually from stress, anxiety, or task saturation.
• The symptoms overlap badly with hypoxia: lightheadedness, tingling, visual disturbance, and eventually unconsciousness.
• Because you can't reliably tell them apart in the moment, if you're at altitude assume hypoxia first. Go to oxygen and descend.
• If that doesn't resolve it, treat the hyperventilation: consciously slow your breathing rate, talk out loud, or breathe into a bag to bring carbon dioxide levels back up.

• Above 12,500 ft MSL up to and including 14,000 ft MSL - The required minimum flight crew must use oxygen for the portion of the flight at those altitudes lasting more than 30 minutes.
• Above 14,000 ft MSL - The required minimum flight crew must use it the entire time at those altitudes.
• Above 15,000 ft MSL - Each occupant must be provided with supplemental oxygen. They aren't required to use it.

These are cabin pressure altitudes, and they're legal minimums rather than physiological ones. At night, or if you smoke or aren't at your best, consider oxygen well below 12,500 ft. Night vision begins degrading around 5,000 ft.

Gas trapped in body cavities expands and contracts with pressure change. If it cannot escape, pressure builds and you get pain and a temporary loss of hearing.

The middle ear equalizes through the Eustachian tube, which runs to the back of the throat. It is normally closed and opens during chewing, yawning or swallowing.

• Climbing, middle ear pressure exceeds the pressure in the external ear canal and the eardrum bulges outward. You notice it as alternating sensations of fullness and clearing.
• Descending, the reverse: external pressure rises while the middle ear is still at the lower pressure from altitude, bulging the eardrum inward. The resulting partial vacuum constricts the walls of the Eustachian tube, which is why a block almost always happens on the way down.

Clearing a descent block: pinch the nostrils shut, close the mouth and lips, and blow slowly and gently into the mouth and nose. That forces air up the Eustachian tube into the middle ear.

A cold, an ear infection or a sore throat may make equalizing impossible, and flying in that condition can be extremely painful as well as damaging to the eardrums. For minor congestion, nose drops or nasal sprays may reduce the risk, but check with an AME before using any medication.

Sinus block is the same mechanism. The sinuses equalize through small openings into the nasal passages, and a cold, sinusitis or a nasal allergy can congest an opening enough to plug it.

• It also occurs most frequently during descent, and a slow descent rate reduces the pain.
• It hits the frontal sinuses above each eyebrow or the maxillary sinuses in each upper cheek. A maxillary block can also make the upper teeth ache.
• Avoid it by not flying with an upper respiratory infection or nasal allergic condition. If it does not clear shortly after landing, see a physician.