The ATPL Cheat Sheet every memory item, number and trap, all 14 subjects
The facts that actually get tested, stripped to the bone: definitions, key numbers, formulas, mnemonics and the classic exam traps for each subject. Built for the night before, the commute, and the last scroll before you walk into the exam hall.
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Study aid only. This is an independently authored revision summary, not exam material and not affiliated with EASA or any CAA. Figures marked verify and all regulatory limits change over time and vary by aircraft type, so always confirm against the current EASA regulations, AMC/GM and your aircraft AFM. No pass is guaranteed. Copyright SkyStudy, skystudyatpl.com. Free to share unmodified.
The 14 subjects
010
Air Law
Chicago Convention, ICAO Annexes, airspace classes, rules of the air, VFR minima, light signals.
Airspace classes A to G at a glance
A to E are controlled (an ATC service is given); F and G are uncontrolled. Class A is the only class that forbids VFR; class G gives information only.
Must-know definitions and concepts
The Chicago Convention (1944) established ICAO and confirms every state has complete and exclusive sovereignty over the airspace above its territory.
ICAO has 19 Annexes to the Chicago Convention; each contains Standards (must comply, differences must be filed) and Recommended Practices (should comply, no filing obligation).
Key Annexes to know cold: 1 Personnel Licensing, 2 Rules of the Air, 3 Meteorological Service, 6 Operation of Aircraft, 7 Nationality and Registration Marks, 8 Airworthiness, 11 Air Traffic Services, 13 Accident and Incident Investigation, 14 Aerodromes, 17 Security.
The Five Freedoms of the Air: 1st and 2nd are technical (overfly, technical stop), 3rd to 5th are traffic freedoms.
State of Registry: the state on whose register the aircraft is entered; responsible for the Certificate of Registration.
State of the Operator: the state where the operator has its principal place of business; issues the Air Operator Certificate.
Certificate of Airworthiness, Certificate of Registration and Noise Certificate are three separate mandatory documents carried on board.
Civil aircraft versus State aircraft (military, customs, police): State aircraft are not bound by ICAO Annexes.
Airspace classes A to G: A is IFR only, ATC clearance and separation from all traffic; G is uncontrolled, no ATC service, traffic information only on request.
The Pilot-in-Command has final authority and responsibility for the safety of the aircraft and all persons on board.
CAVOK means visibility 10 km or more, no cloud below 5000 ft (or the highest minimum sector altitude if higher), no CB or towering cumulus, no significant weather.
Distress (MAYDAY) = grave and imminent danger requiring immediate assistance. Urgency (PAN PAN) = a safety concern not requiring immediate assistance.
NOTAM: time-critical information not known early enough to publish in the AIP. The AIP is the primary source of permanent aeronautical information for a state.
Annex 13 accident and incident investigations exist solely to prevent future accidents, never to apportion blame or liability.
Key numbers, limits and values
SSR transponder codes: 7500 unlawful interference (hijack), 7600 radio failure, 7700 general emergency.
Emergency frequency 121.5 MHz (civil); 243.0 MHz military. ELT transmits on 121.5 MHz and 406 MHz.
ISA: sea level 1013.25 hPa (29.92 inHg), 15 C, lapse rate about 1.98 C per 1000 ft (rounded to 2 C/1000 ft).
Pressure decreases by roughly 1 hPa per 30 ft near sea level (the ratio changes with altitude).
QNH: reads elevation AMSL on the ground. QFE: reads height above the aerodrome. QNE: standard 1013.25 hPa above the transition altitude.
Semicircular rule: magnetic track 000 to 179 flies odd thousands; 180 to 359 flies even thousands (add 500 ft for VFR where applicable).
Transition altitude is fixed by the state/aerodrome (flown on QNH); transition level is calculated by ATC and varies with pressure (flown on 1013.25).
VFR at and above 10,000 ft AMSL: 8 km visibility, 1500 m horizontal and 300 m (1000 ft) vertical from cloud.
VFR below 10,000 ft down to 3000 ft AMSL: 5 km visibility, 1500 m horizontal and 300 m vertical from cloud.
VFR at or below 3000 ft AMSL (or 1000 ft above terrain) in class F/G: 5 km visibility, clear of cloud, in sight of the surface.
Minimum height: 1000 ft above the highest obstacle within 600 m over congested areas; elsewhere not within 500 ft of any person, vehicle, vessel or structure.
Runway designators are the magnetic bearing of the centreline rounded to the nearest 10 degrees, last digit dropped (274 becomes 27).
Right of way order: aircraft in distress, then balloons, gliders, airships, aircraft towing, then powered heavier-than-air aircraft.
Converging same-category aircraft: the one with the other on its right gives way. Head-on: both turn right. Overtaking: overtaker alters right, overtaken has right of way.
Aircraft on final approach to land has right of way over aircraft on the ground or about to take off. Time in aviation is always UTC.
Alcohol: a common minimum is 8 hours bottle to throttle verify.
Light signals to aircraft in flight: steady green = cleared to land; steady red = give way and keep circling; flashing green = return to land; flashing red = aerodrome unsafe, do not land.
Light signals to aircraft on the ground: steady green = cleared for takeoff; flashing green = cleared to taxi; steady red = stop; flashing red = taxi clear of the runway in use; flashing white = return to starting point.
Mnemonics and memory items
Anchor the Annexes by number: 1 Licensing, 2 Rules of the Air, 3 Met, 6 Operations, 7 Marks, 8 Airworthiness, 11 ATS, 13 Investigation, 14 Aerodromes, 17 Security.
Right of way pecking order: Big Girls Always Take Priority (Balloons, Gliders, Airships, Towing, Powered).
MAYDAY = Menace (grave danger), PAN = Precaution (urgent, not yet grave). Each is said three times.
Squawk ladder by severity: 7500 hijack, 7600 comms lost, 7700 general emergency.
Cloud clearance hook 1-5-3: 1500 m horizontal, 300 m (1000 ft) vertical, at every VFR band above the surface layer.
QNH = height above sea level; QFE reads zero on the Field.
Common exam traps
Do not confuse State of Registry (Certificate of Registration, aircraft) with State of the Operator (AOC, operator).
Standards are not automatically law everywhere: states may file differences; Recommended Practices carry no filing obligation.
Transition altitude is fixed; transition level changes with QNH. Do not swap them.
On converging tracks, the aircraft that gives way is the one with the other on its right, not the faster or first-arriving one.
When overtaking, the overtaking aircraft alters right and the overtaken aircraft keeps its heading; students often reverse this.
Powered aircraft give way to balloons, gliders and airships regardless of which side they are on.
CAVOK has strict thresholds; weather just short of them is not CAVOK even if it looks fine.
7500 gives no aural warning to the crew that set it; do not assume all three emergency codes behave the same.
State aircraft (military, customs, police) are exempt from ICAO Annexes.
Runway numbers round the magnetic bearing, not the true bearing; convert first if a true heading is given.
Exam figures from the SkyStudy question bank
Two of the 369 code-drawn study figures inside the SkyStudy question bank. Try them with the free demo at skystudyatpl.com/demo.
Airframe and structures, hydraulics, pneumatics, electrics, engines, propellers, systems.
AC and DC electrical generation chain
Constant-frequency AC: the CSD/IDG holds generator input speed so output stays at 400 Hz. Transformer-rectifier units feed the 28 V DC bus and battery. Modern types (e.g. B787) generate variable-frequency AC and delete the CSD; a RAT gives last-resort emergency power.
Must-know definitions and concepts
Primary structure is monocoque (skin carries all loads) or semi-monocoque (skin plus stringers and frames share loads); semi-monocoque is standard on transport aircraft.
Fail-safe design keeps adequate residual strength after a single element fails, until damage is found at the next inspection.
Damage tolerance: structure and inspection are designed so a crack grows without catastrophic failure before detection.
Fatigue: cyclic loading (pressurisation cycles, gusts) causes crack initiation and growth over time, independent of a single overload.
Hydraulics: engine-driven pumps pressurise fluid, reservoirs allow for volume change, accumulators store pressure and dampen pulses; most transports use 3000 psi (some newer types 5000 psi).
Pneumatic (bleed air): hot high-pressure air tapped from the compressor powers air conditioning, pressurisation, anti-ice and engine start.
The Air Cycle Machine cools bleed air using the Brayton refrigeration cycle (compress, cool, expand), not a vapour cycle.
Pressurisation: the outflow valve modulates cabin air exit to hold a scheduled cabin altitude and fails to a safe (open) position on loss of power.
Ice protection: thermal (hot bleed air or electric), pneumatic boots (inflate to crack ice off), and fluid (weeping wing / TKS).
Anti-ice prevents ice continuously; de-ice lets ice form then removes it cyclically.
AC generation: engine-driven generators produce three-phase AC, typically 115/200 V at 400 Hz on constant-frequency systems.
A Constant Speed Drive (CSD/IDG) turns variable engine speed into a constant generator input speed so output stays at 400 Hz.
Modern Variable Frequency systems (e.g. B787) generate variable-frequency AC and convert as needed, removing the CSD.
RAT (Ram Air Turbine) deploys automatically to give emergency hydraulic and/or electrical power after major power loss.
The squat switch (weight-on-wheels) switches logic between air mode and ground mode (spoilers, reverse, radio-altimeter callouts, pressurisation).
Oxygen: gaseous cylinders for the crew, chemical generators (sodium chlorate) for passenger drop-down masks on most narrowbodies.
Bypass ratio: fan bypass mass flow divided by core mass flow; high-bypass engines are more efficient and quieter at airline cruise speeds.
Constant-speed (variable-pitch) propellers use a governor to hold selected RPM by varying blade angle; feathering aligns blades with the airflow to stop windmilling drag.
Key numbers, limits and values
Standard transport AC frequency: 400 Hz; generator output 115 V line-to-neutral / 200 V line-to-line, three-phase.
Typical hydraulic pressure 3000 psi; some modern types 5000 psiverify.
Maximum certificated cabin altitude for a pressurised transport at max operating altitude: 8000 ft.
Cabin altitude warning typically triggers around 10,000 ft cabin altitude verify.
Aircraft DC bus typically 28 V DC; battery commonly 24 V (Ni-Cd or lead-acid), fed via transformer-rectifier units.
Turbine gas temperature limits (EGT/ITT/TGT) are engine-type specific and lowest at start; do not memorise a generic number verify.
Fire protection: typically two bottles per engine, discharged from the flight deck.
V-speeds are aircraft-specific; for 021 learn the definitions, not fixed numbers.
ISA reference for systems work: 1013.25 hPa, 15 C, 1.98 C/1000 ft to the tropopause at 36,090 ft.
Formulas and relationships
Otto cycle efficiency rises with compression ratio (idealised constant-volume heat addition).
Brayton cycle efficiency rises with overall pressure ratio (idealised constant-pressure heat addition).
Thrust is proportional to mass flow times change in velocity (Newton's third law).
AC output frequency is proportional to rotational speed, f = (pole pairs x RPM)/60, so the CSD must hold input speed constant for 400 Hz.
Gas law PV = nRT underlies pressurisation and bleed systems: compressing bleed air raises pressure and temperature, so it needs cooling before cabin use.
Basic electrical relationships V = IR and P = VI apply to DC systems, generator loading and load-shedding.
Mnemonics and memory items
Anti before, De after: anti-ice prevents ice, de-ice removes it once formed.
CSD keeps it constant: Constant Speed Drive gives a constant 400 Hz.
Brayton = continuous burn (turbine); Otto = one bang per two revolutions (piston).
Squat switch: weight on wheels = ground logic; weight off wheels = air logic.
Feathered blades turn edge-on to the wind (flat to the flow) to kill drag.
RAT deploys when you lose the juice: last-resort emergency power.
Common exam traps
Do not confuse anti-ice (continuous prevention) with de-ice (cyclic removal); boots are de-ice, hot leading edges are usually anti-ice.
Do not swap Otto (piston, intermittent, constant-volume) with Brayton (turbine, continuous, constant-pressure).
400 Hz is the standard constant frequency, but not every modern aircraft uses fixed frequency; some use variable-frequency generation with converters.
Cabin altitude and aircraft altitude differ: the cabin is always at a lower altitude (higher pressure) than the aircraft in cruise; the 8000 ft limit is a design limit, not a target.
Accumulators store energy and dampen pulses; the pump is the source of sustained pressure.
The propeller governor controls blade angle to hold RPM; the power lever sets power, the RPM lever sets the governor target.
Weight-on-wheels logic gates many unrelated systems (spoiler arming, autobrake, reverse, radio-altimeter callouts).
Do not conflate fail-safe (structural redundancy) with damage tolerance (inspection-driven crack management).
Exam figures from the SkyStudy question bank
Two of the 369 code-drawn study figures inside the SkyStudy question bank. Try them with the free demo at skystudyatpl.com/demo.
Pitot-static, gyroscopes, magnetic compass, IRS/AHRS, EFIS, warning systems.
Pitot-static system and its instruments
ASI needs both total and static; the altimeter and VSI use static only. Blocked static: altimeter freezes and VSI reads zero, ASI over-reads in a descent and under-reads in a climb. Blocked pitot (drain blocked): the ASI behaves like an altimeter.
Must-know definitions and concepts
Pitot pressure = static (ambient) + dynamic (impact); the pitot tube senses total pressure, static ports sense ambient only.
IAS is the raw reading; CAS = IAS corrected for instrument and position error.
EAS = CAS corrected for compressibility (significant only at high speed/altitude).
TAS = EAS corrected for density (temperature and altitude); TAS exceeds CAS increasingly with altitude.
The altimeter is an aneroid capsule sensing static pressure, calibrated to ISA; QNH reads elevation AMSL, QFE reads zero on the field, QNE (1013.25 set) gives pressure altitude.
The VSI senses rate of change of static pressure through a calibrated leak; an IVSI adds an accelerometer pump to remove lag.
The Machmeter compares dynamic to static pressure for Mach number and needs no temperature input, unlike a TAS computation.
Rigidity in space: a spinning mass resists change to its plane of rotation, proportional to spin speed and moment of inertia.
Precession: a force applied to a spinning gyro is felt 90 degrees later in the direction of rotation.
Real (Earth) wander is apparent drift from Earth rotating beneath a space-fixed gyro; transport wander is drift from the aircraft moving over the curved Earth.
The attitude indicator uses an earth gyro with a pendulous erection system for the gravity vertical.
The directional gyro/HSI uses a tied gyro that must be reset against the magnetic compass because it is not Earth-referenced.
The turn indicator is a rate gyro precessing against a spring in proportion to turn rate; the slip ball beside it is a simple pendulum, not gyroscopic.
Magnetic dip is the angle between the local field vector and the horizontal; it causes direct-reading compass turning and acceleration errors.
IRS uses strapdown ring-laser or fibre-optic gyros (Sagnac effect, no spinning mass) plus accelerometers, deriving position by double integration.
AHRS gives attitude and heading only (no navigation), using strapdown sensors plus a magnetometer.
The radio altimeter measures true height above the terrain directly below (AGL), not AMSL.
The Air Data Computer turns pitot, static and total-air-temperature inputs into altitude, CAS, TAS, Mach and VS for displays, autopilot, transponder and FMS.
EFIS splits into the PFD (attitude, speed, altitude) and ND (navigation/map). The FMS adds a nav database and performance computer for lateral and vertical navigation (LNAV/VNAV).
Key numbers, limits and values
ISA sea level: 15 C (288 K), 1013.25 hPa, 29.92 inHg, 760 mmHg.
ISA lapse rate 1.98 C per 1000 ft (rounded to 2) to the tropopause.
ISA tropopause: 36,090 ft (11,000 m), -56.5 C, constant above.
Speed of sound at ISA sea level about 661.5 kt (340.3 m/s).
Rate 1 standard turn = 3 deg/sec (360 in 2 minutes); Rate half = 1.5 deg/sec at high TAS verify.
RVSM: FL290 to FL410 inclusive, 1000 ft separation; 2000 ft above FL410.
Magnetic dip: 0 deg at the magnetic equator, 90 deg at the magnetic poles.
Compass turning error is maximum turning through North or South, zero through East or West.
Compass acceleration error is maximum on East/West headings, zero on North/South.
Radio altimeter usable range roughly 0 to 2500 ft AGLverify.
GPWS classic modes 1 to 6; EGPWS adds a forward-looking terrain database and windshear mode verify.
TCAS II issues Resolution Advisories in the final seconds, Traffic Advisories earlier; RAs are vertical only verify.
Stall warning (stick shaker) triggers at a set margin above the stalling angle of attack, not from IAS alone verify.
Formulas and relationships
Mach number = TAS / Local Speed of Sound.
LSS (kt) is about 38.95 x sqrt(absolute temperature in K); it depends on temperature only.
Rule of thumb: TAS is about 2% above CAS per 1000 ft for a constant CAS (an ISA approximation).
Standard-rate (Rate 1) bank angle is about TAS(kt)/10 + 7 degrees.
Precession rate is proportional to applied torque and inversely proportional to angular momentum (spin x moment of inertia); more momentum means more rigidity.
Pressure altitude is what the altimeter reads with 1013.25 set; true altitude equals indicated only in ISA conditions, else high to low, look out below.
Mnemonics and memory items
ONUS: Overshoot North, Undershoot South, the compass turning error (Northern Hemisphere; reverses in the South).
ANDS: Accelerate North, Decelerate South, the compass acceleration error (Northern Hemisphere; reverses in the South).
High to low, look out below: flying into lower pressure or colder air, true altitude is below indicated.
Turning error worst on N/S, acceleration error worst on E/W: complementary, not the same axis.
Precession is felt 90 degrees later in the direction of spin: the key to every gyro-error question.
Rigidity keeps a gyro pointing the same way; precession is the only thing that moves it.
Common exam traps
A blocked static freezes the altimeter and zeroes the VSI; the ASI then under-reads in a climb and over-reads in a descent.
A blocked pitot with the drain also blocked makes the ASI act like an altimeter: it over-reads in a climb, under-reads in a descent.
A blocked pitot with the drain clear lets the ASI fall toward zero.
Compressibility error depends on speed and altitude (a dynamic-to-static pressure ratio), not speed alone.
The Machmeter needs no temperature correction; do not apply the TAS temperature correction to it.
Compass dip errors affect the direct-reading compass only; gyro instruments suffer real/transport wander and drift instead.
Do not confuse VSI lag during rapid pitch changes with an actual fault.
The radio altimeter reads AGL over the terrain below, so over rising or falling ground it will not track the pressure altimeter.
TCAS/ACAS resolution advisories are vertical only; TCAS never gives turn guidance.
Stall warning triggers from angle of attack, not IAS; an iced or mis-rigged AoA vane is the classic failure cause.
Exam figures from the SkyStudy question bank
Two of the 369 code-drawn study figures inside the SkyStudy question bank. Try them with the free demo at skystudyatpl.com/demo.
Mass definitions, centre of gravity, MAC, load and trim, standard masses.
Mass build-up and the CG envelope
Build-up: BEM to DOM (add crew, catering) to ZFM (add payload) to TOM (add fuel); LM = TOM minus trip fuel. The CG must stay inside the envelope at every mass, and no mass may exceed MTOM, MLM or MZFM.
Must-know definitions and concepts
Basic Empty Mass (BEM): airframe, engines, fixed equipment, unusable fuel and fixed ballast; excludes crew, consumables and payload.
Dry Operating Mass (DOM/OEM): BEM plus crew, crew baggage, catering, potable water and removable operational equipment; excludes payload and usable fuel.
Zero Fuel Mass (ZFM): DOM plus traffic load; the aircraft with no usable fuel.
Take-off Mass (TOM): ZFM plus take-off fuel. Landing Mass (LM): TOM minus trip fuel.
Traffic load (payload): passengers, baggage, cargo and mail; equals ZFM minus DOM.
Useful load: traffic load plus usable fuel; about MTOM minus DOM, subject to the limiting mass.
MTOM, MLM, MZFM are maximum structural/regulatory limits; none may be exceeded whatever the underload elsewhere.
Underload: the margin between the actual mass and the most restrictive limiting mass for that flight.
Datum: a reference point (can even be ahead of the nose) from which all arms are measured; chosen for convenience.
Arm: distance from the datum to an item CG; moment = mass x arm (the turning effect about the datum).
Centre of Gravity (CG): the single point at which total weight is considered to act.
Mean Aerodynamic Chord (MAC): the reference chord against which CG position is expressed.
%MAC: CG position as a percentage of MAC length, measured aft of the leading edge of MAC (LEMAC).
Index unit: a scaled, dimensionless moment used on loadsheets to keep numbers small and positive.
Forward CG effects: more longitudinal stability, higher stall speed, more nose-down pitch needing tailplane download (more trim drag), more elevator needed to rotate.
Aft CG effects: less stability, lower stall speed, less trim drag and better range, but reduced stall/spin recovery margin and lighter control feel.
Cargo floor loading is limited by a running load (kg per metre) and an area load (kg per square metre), separate from the compartment mass limit.
Key numbers, limits and values
Standard passenger mass, 20+ seats: male 88 kg, female 70 kg, child (2 to under 12) 35 kg, including hand baggage verify.
Standard crew mass: flight crew 85 kg, cabin crew 75 kg, including crew hand baggage verify.
Standard checked baggage commonly taught: about 13 kg short/medium-haul, 15 kg intercontinental verify.
Fuel density varies. Training problems commonly use a nominal 0.8 kg/L, but use the actual density from the docket or gauge when given (Jet A-1 is typically 0.775 to 0.840 kg/L) verify.
1 US gallon is about 3.785 L; 1 Imperial gallon is about 4.546 L; 1 kg is about 2.2046 lb.
MTOM, MLM, MZFM, the CG limits, LEMAC, MAC length and index constants are all aircraft-type specific; never assume a generic value.
CG limits are often plotted on an envelope and can narrow at low or high mass.
Formulas and relationships
Moment = Mass x Arm.
Combined CG arm = Total moment / Total mass = sum(mass_i x arm_i) / sum(mass_i).
%MAC = ((CG arm - LEMAC arm) / MAC length) x 100.
Adding mass: New CG = (Old moment + added mass x its arm) / (Old mass + added mass).
Removing mass: New CG = (Old moment - removed mass x its arm) / (Old mass - removed mass).
Shifting mass: CG change = (mass shifted x distance shifted) / Total mass.
Mass to shift for a required CG change = (Total mass x required CG change) / distance shifted.
Index = (Mass x Arm / reduction constant) + reference constant (type-specific).
ZFM = DOM + Traffic load; TOM = ZFM + Take-off fuel; LM = TOM - Trip fuel.
Underload = limiting mass (MTOM/MLM/MZFM) - actual mass at that stage.
Mnemonics and memory items
Build-up order Basic, Dry, Zero, Take-off, Land (BEM, DOM, ZFM, TOM, LM): each step adds or removes one category.
Treat every problem as a lever: Moment = Mass x Arm, like torque = force x distance.
CG = Total moment over Total mass, never masses alone.
Forward CG: more stable, higher stall speed, more trim drag. Aft CG: less stable, lower stall speed, less drag.
%MAC starts at LEMAC: always measured aft of the leading edge of the MAC, not from the datum.
The datum is a choice, not a landmark; the index is just moment, shrunk and shifted.
Common exam traps
Do not confuse DOM (no payload) with ZFM (no usable fuel).
Do not add unusable fuel or fixed ballast again; they are already inside BEM.
Check the arm sign convention: some datums make forward arms negative, others keep all arms positive.
Use the given fuel density, not a fixed 0.8 kg/L, when a docket value is supplied.
%MAC and index units are two different scaled representations of the same CG; they are not interchangeable without the type conversion data.
Checking only TOM against MTOM can miss that MLM or MZFM is the limiting figure.
Shifting cargo changes CG but not total mass, so ZFM/TOM/MLM checks are unaffected by a shift; only CG/%MAC needs rework.
Do not double count crew baggage or catering already folded into DOM.
Do not freely mix standard and actual mass methods within one passenger/baggage category on a flight.
A concentrated load can breach a floor load limit while under the compartment mass limit.
Exam figures from the SkyStudy question bank
Two of the 369 code-drawn study figures inside the SkyStudy question bank. Try them with the free demo at skystudyatpl.com/demo.
Performance classes, V-speeds, takeoff and landing, climb segments, WAT limits.
Class A take-off climb segments (one engine inoperative)
1 gear retracting, gradient positive. 2 steepest climb, gear up, to at least 400 ft (min 2.4% twin, 2.7% tri, 3.0% quad). 3 level acceleration, flaps retract. F en-route climb at MCT (min 1.2 / 1.5 / 1.7%). All one-engine-inoperative for Class A.
Must-know definitions and concepts
Class A: multi-engine turbine, MTOM over 5700 kg or over 9 seats, or any turbojet; full engine-failure accountability at every stage.
Class B: propeller aeroplanes, 9 seats or fewer and MTOM 5700 kg or less; simplified rules, no guaranteed OEI climb below the screen height.
Class C: larger aeroplanes not meeting A or B (mostly older large piston types).
V1 (decision speed): stop by V1 to remain within ASDA; at or above V1, continue and reach V2 by the screen height after a recognised failure.
VR (rotation): not less than V1, not less than 1.05 x VMCA, set so V2 is reached by the screen height.
V2 (takeoff safety speed): target by the screen height with one engine inoperative, giving the certified climb margin above stall and VMCA.
VMCG: minimum ground speed to keep directional control after critical-engine failure using rudder alone.
VMCA: minimum airborne speed to keep directional control with the critical engine out and a limited bank into the live engine.
VMU minimum unstick, VEF assumed engine-failure speed, VLOF lift-off speed, VMBE max brake energy speed.
VS/VS0/VS1/VSR: stall speeds and the reference stall speed used as the basis for V-speed margins.
Balanced field: V1 chosen so the OEI accelerate-go distance equals the accelerate-stop distance, minimising required runway.
TORA/TODA/ASDA/LDA: the four declared distances. Clearway extends TODA only; stopway extends ASDA only.
Class A takeoff segments: 1st (gear retracting, one engine inoperative), 2nd (gear up, steepest, OEI), 3rd (level acceleration, flaps up), final (climb to safe en-route altitude, MCT, OEI).
Gross flight path is demonstrated performance; net is gross reduced by a certification decrement and is what obstacle clearance is checked against.
WAT limit (Weight, Altitude, Temperature): the maximum mass at which the required climb gradient is still met.
Drift-down: the planned descent schedule flown after an engine failure in cruise when altitude cannot be held, checked against the net flight path.
PNR is the last point a return is possible with required reserves; ETP/PET is where time to continue equals time to turn back.
Key numbers, limits and values
Takeoff screen height 35 ft dry; a reduced 15 ft is allowed on a wet runway under certain provisions verify.
VR not less than 1.05 x VMCA; V2 not less than about 1.13 x VSR for most turbojets verify.
VMCG lateral deviation limit about 30 ft from centreline; VMCA demonstration bank angle limited to about 5 degrees into the live engine verify.
Final segment minimum about 1.2% twin, 1.5% three-engine, 1.7% four-engine verify.
Approach climb (OEI, go-around) about 2.1% twin, 2.4% three-engine, 2.7% four-engine; landing climb (all engines) about 3.2%verify.
1st segment gradient must be positive; 3rd segment is a level acceleration with no gradient requirement, commonly around 400 ft AGL verify.
Dispatch landing factor, turbojet: about x1.67 dry, x1.92 wet. Turboprop: about x1.43 dry, x1.64 wetverify.
Landing distance is measured from a 50 ft screen over the threshold to a full stop (distinct from the takeoff screen).
ASDA = TORA + stopway; TODA = TORA + clearway.
En-route OEI obstacle corridor commonly taught as about 5 NM either side of track, with at least 1000 ft net vertical clearance (more in mountainous areas) verify.
Wind rule of thumb: about 50% credit for headwind, 150% penalty for tailwind.
Formulas and relationships
Climb gradient (%) is about (Rate of Climb / TAS) x 100, both in the same units (1 kt is about 101.3 ft/min).
Specific air range is about TAS / fuel flow (distance per unit fuel).
ETP distance from departure = (total distance x GS toward the point) / (GS out + GS back).
As chosen V1 increases, accelerate-stop distance grows while accelerate-go shrinks; balanced V1 is where they cross.
Required takeoff distance (Class A) is the greater of the OEI distance to the screen or a factored all-engine distance.
V-speeds and stall speed rise with the square root of weight, so higher mass raises V1/VR/V2 and lengthens all distances.
For fixed altitude and temperature, the WAT-limited mass is the mass at which the required gradient is exactly met.
Fuel policy, PET and PNR, ICAO flight plan, cruise techniques, altimetry.
PET and PNR, and the fuel build-up
PET depends on geometry only; a headwind out moves it toward the destination. PNR depends on endurance; any wind reduces its range. Fuel order upward: Taxi, Trip, Contingency, Alternate, Final reserve, Additional, Extra.
Must-know definitions and concepts
Trip fuel: brake release at departure to touchdown at destination (takeoff, climb, cruise, descent, approach, landing).
Taxi fuel: fuel used before takeoff, including APU and expected delay.
Contingency fuel: covers deviations from plan; normally the higher of a percentage of trip fuel or a time-based allowance verify.
Alternate fuel: from the missed approach at destination to landing at the destination alternate, including one approach and landing.
Final reserve: a fixed holding time at 1500 ft above the alternate (or destination if none), at estimated landing mass.
Additional fuel: for engine or pressurisation failure at the critical point, or flight to an isolated aerodrome with no usable alternate.
Extra/discretionary fuel: carried at the commander's discretion above the required minimum.
Isolated aerodrome: no suitable alternate in range, needing additional fuel instead of alternate fuel.
Point of Equal Time (PET) / Critical Point: the point from which time to continue equals time to return.
Point of No Return (PNR): the furthest point from which a safe return to departure is still possible with the endurance available.
Redispatch/reclearance: dispatch to an intermediate point with a new plan filed for continuation once airborne, to reduce the required fuel load.
ICAO flight plan (FPL): the standardised ATC/ATFM form; distinct from the operational (company) flight plan used for fuel and performance.
Network Manager (Eurocontrol): manages European flow, issues ATFM slots (CTOT); the RAD publishes permitted and prohibited route segments.
Conditional Route (CDR): usable only under stated conditions (CDR1 always plannable, CDR2 per AUP/NOTAM, CDR3 tactical only).
LRC gives about 99% of maximum range for a useful speed gain; max range gives the greatest still-air distance per fuel; max endurance gives minimum fuel flow.
Transition altitude/level/layer: at or below the TA use altitude on QNH; above the TL use flight levels on 1013.25; do not level in the layer between.
Key numbers, limits and values
Contingency: the higher of 5% of trip fuel or a time-based holding allowance verify.
Final reserve: 30 minutes for turbine (jet/turboprop), 45 minutes for piston, holding at 1500 ft in standard conditions verify.
Standard pressure setting (QNE) for flight levels: 1013.25 hPa (29.92 inHg).
MINIMUM FUEL call: committed to an aerodrome where any extra delay would land below final reserve; it is not a distress call.
MAYDAY FUEL call: predicted usable fuel on landing at the nearest suitable aerodrome will be below final reserve; this is distress.
FPL wake categories (Item 9): L Light, M Medium, H Heavy, J Super.
FPL flight rules (Item 8): I (IFR), V (VFR), Y (IFR then VFR), Z (VFR then IFR).
FPL type of flight (Item 8): S scheduled, N non-scheduled, G general aviation, M military, X other.
Semicircular levels: odd for magnetic track roughly 000 to 179, even for 180 to 359 verify.
Formulas and relationships
PET distance from departure = D x H / (O + H), where D = total distance, O = groundspeed out, H = groundspeed home.
PNR time from departure = E x H / (O + H), where E = safe endurance as time, O = groundspeed out, H = groundspeed home.
Time to PET = PET distance / O; PNR distance = PNR time x O.
With no wind (O = H), PET is at the mid-point D/2 and PNR is at maximum range for the endurance.
A headwind out / tailwind home moves PET toward the destination; any wind (versus still air) moves PNR closer to departure, reducing range.
Specific air range (SAR) = distance per unit fuel; LRC and max-range speeds sit at or near the peak of the SAR curve.
Mnemonics and memory items
Fuel build-up Taxi, Trip, Contingency, Alternate, Final reserve, Additional, Extra.
PET splits the trip in time; PNR is the last chance to turn back.
Keep the letters straight: O is Out, H is Home; swap them and the answer flips.
Minimum fuel is a heads-up; Mayday fuel is an emergency.
LRC = a little less range, a lot more speed (about 1% range traded).
Going up: QNH to QNE at the transition altitude. Coming down: QNE to QNH at the transition level.
Common exam traps
PET is a time-equality point (independent of fuel); PNR is endurance-limited. Do not conflate them.
Do not swap O and H; confirm which groundspeed is outbound and which is the return.
PET is at the mid-point only in zero wind; wind shifts it toward the less favourable leg.
Final reserve is the minimum fuel on landing, not a planning allowance to dip into en route.
Do not mix the 30 min (turbine) and 45 min (piston) reserves; a turboprop uses the turbine figure verify.
Contingency is normally the higher of the two methods, not always 5%.
Do not confuse QNH (altitude AMSL), QFE (height above aerodrome) and QNE (flight levels on 1013.25).
FPL Item 10a is COM/NAV/approach equipment; Item 10b is surveillance equipment (transponder, ADS: Automatic Dependent Surveillance); do not merge them.
Restricted route segments in the RAD will get the plan rejected or delayed by ATFM.
Redispatch reduces the required minimum, it does not exempt the flight from carrying adequate fuel for the routing actually flown.
Max endurance speed is lower than max range speed; a MAYDAY FUEL situation needs the MAYDAY call, not MINIMUM FUEL.
Exam figures from the SkyStudy question bank
These two come from SkyStudy's KSA (100) mental-maths set; they are the exact methods 033 planning questions test. Two of the 369 code-drawn study figures inside the SkyStudy question bank. Try them with the free demo at skystudyatpl.com/demo.
Physiology, hypoxia, vision, illusions, sleep and fatigue, CRM and error.
Time of Useful Consciousness versus altitude
Approximate, seated at rest. A rapid or explosive decompression roughly halves these times. TUC is the time to loss of useful action, not the time to unconsciousness. Values vary by individual, so confirm against current teaching.
Must-know definitions and concepts
Atmosphere by volume: about 21% oxygen, 78% nitrogen, roughly 1% other gases.
Partial pressure of a gas = total pressure x fractional concentration (Dalton's Law); alveolar oxygen partial pressure falls with altitude even though the 21% fraction is constant.
Hypoxic hypoxia: too little oxygen reaching the blood from reduced ambient partial pressure (the classic altitude hypoxia).
Hypemic (anaemic) hypoxia: reduced oxygen-carrying capacity (anaemia, blood loss, or carbon monoxide binding to haemoglobin).
Stagnant hypoxia: enough oxygen in the blood but poor circulation (cold, positive G, shock, poor posture).
Histotoxic hypoxia: oxygen delivered but tissues cannot use it (alcohol, some drugs, cyanide).
Hyperventilation: over-breathing washes out CO2 (hypocapnia), mimicking hypoxia but with normal or high oxygen.
Stages of hypoxia: indifferent, compensatory, disturbance, critical.
Time of Useful Consciousness (TUC): time from onset of hypoxia to the loss of effective corrective action.
Pressurised cabins are typically held around 6,000 to 8,000 ft equivalent, not sea level.
Explosive/rapid decompression is more dangerous than gradual because TUC is shortened and lung barotrauma risk rises.
G-force sequence with increasing positive G: grey-out (peripheral vision loss), blackout (total vision loss, still conscious), then G-LOC (loss of consciousness). Negative G gives redout.
The retina has rods (peripheral, low light, motion, no colour) and cones (central, colour, detail, need light).
Dark adaptation of rods takes around 30 minutes and is lost quickly in bright light; use off-centre viewing at night.
Empty-field myopia: in a featureless field the eyes default-focus short (about arm's length), reducing distant traffic detection.
The vestibular system (semicircular canals plus otoliths) senses angular acceleration (canals) and linear acceleration/gravity (otoliths), not attitude directly.
The leans: a slow roll below the canals' detection threshold is not sensed, so the pilot feels wings-level when banked.
Coriolis illusion: a head movement during a sustained turn stimulates several canals at once, causing strong disorientation.
Somatogravic illusion: forward acceleration (e.g. takeoff) feels like a nose-up pitch, tempting a nose-down input.
Somatogyral illusion: a sustained turn feels to slow or stop, so rolling level feels like a turn the other way (graveyard spiral risk).
Black hole approach: over dark, featureless terrain with only runway lights, pilots feel too high and fly dangerously low.
Middle ear and sinus barotrauma is worse on descent. Decompression sickness (DCS) is a separate problem: nitrogen leaving solution as pressure falls.
Circadian rhythm is the roughly 24-hour body clock; the WOCL (window of circadian low) is the least-alert period, roughly 02:00 to 06:00 body time.
Yerkes-Dodson law: performance rises with arousal to an optimum, then falls (inverted-U).
Memory has three stores: sensory (very brief), short-term/working (limited), and long-term (large, durable).
The SHELL model describes the interfaces around the central Liveware (Software, Hardware, Environment, other Liveware).
Reason's Swiss cheese model: accidents happen when weaknesses in successive defences line up.
CRM is the effective use of all resources (people, procedures, equipment) through communication, teamwork and workload management, not stick-and-rudder skill.
Typical maximum cabin altitude around 8,000 ftverify.
TUC (seated, at rest, approximate, verify): 18,000 to 20,000 ft about 20 to 30 min; 25,000 ft about 3 to 5 min; 30,000 ft about 1 to 2 min; 35,000 ft about 30 to 90 s; 40,000 ft+ about 15 to 20 s.
Sudden/explosive decompression roughly halves TUC versus gradual verify.
Dark adaptation to near-maximum rod sensitivity takes up to about 30 minutesverify.
WOCL roughly 02:00 to 06:00 body-clock time; a sleep cycle is about 90 minutesverify.
Adults need about 7 to 8 hours sleep per 24 hours verify.
Working memory capacity is classically 7 plus or minus 2 chunks, held for about 15 to 30 seconds without rehearsal verify.
Flying after diving: commonly at least 12 hours after a single no-decompression dive, at least 24 hours after repetitive or decompression dives verify.
Alcohol is metabolised at roughly one unit per hour; a commonly cited minimum is 8 hours bottle to throttle verify.
Unprotected positive-G tolerance before G-LOC is roughly 4 to 6 G depending on onset rate and the individual verify.
ISA, pressure and altimetry, cloud, wind, fronts, icing, thunderstorms.
Warm and cold fronts in a depression
Cold front (behind): steep slope, cumuliform Cb, showery and squally, passes quickly. Warm front (ahead): shallow slope, layered Ns, As, Cs, Ci with prolonged steady rain. Between them lies the mild, moist warm sector.
Must-know definitions and concepts
ISA is a fixed reference atmosphere for altimetry, performance and calibration; it is not the real atmosphere.
The troposphere is where temperature falls with height (the ELR) and almost all weather occurs; the tropopause caps it and is higher/warmer over the tropics, lower/colder over the poles.
ELR (Environmental Lapse Rate) is the actual measured rate on the day; it varies constantly.
DALR (Dry Adiabatic Lapse Rate) is how fast an unsaturated parcel cools when it rises, from expansion alone.
SALR (Saturated Adiabatic Lapse Rate) is less than the DALR because condensation releases latent heat.
Stability compares ELR to DALR/SALR: a displaced parcel warmer than its surroundings keeps rising (unstable), colder sinks back (stable).
A temperature inversion (temperature rising with height) is very stable and traps moisture, smoke and haze below it.
Dewpoint (Td) is the temperature to which air must cool to become saturated; the dewpoint spread (T minus Td) shrinks toward saturation.
Geostrophic wind: balance of pressure gradient and Coriolis force, parallel to straight isobars (above the friction layer).
Gradient wind adds centripetal force for curved isobars; surface friction backs and slows the wind, so it crosses isobars toward low pressure.
Thermal wind is the vector difference between geostrophic winds at two levels, from horizontal temperature gradients.
A col is a flat-gradient saddle between two highs and two lows; a trough is elongated low pressure, a ridge elongated high pressure.
An air mass has fairly uniform temperature and humidity from its source region; a front is the boundary between two air masses.
A warm front has a shallow slope: long, gradual cloud (Ci, Cs, As, Ns) and prolonged steady rain. A cold front has a steep slope: narrower, vigorous cumuliform cloud with showery, squally rain.
An occlusion forms when the cold front catches the warm front and lifts the warm sector aloft.
Radiation fog forms over land on clear, calm, humid nights; advection fog forms when warm moist air moves over a colder surface and needs some wind to persist.
Rime ice (small supercooled droplets, stratiform) is rough and opaque; clear ice (large droplets, freezing rain, cumuliform) is smooth, hard and more hazardous.
A thunderstorm needs moisture, instability and a trigger; its life cycle is cumulus (updrafts), mature (up and down drafts, heaviest weather), dissipating (downdrafts).
A gust front is the leading edge of the cold downdraft outflow; a microburst is a small, intense downdraft giving sudden severe windshear on takeoff and landing.
CAT (Clear Air Turbulence) occurs in cloud-free air, most often near jet streams and the tropopause; mountain waves form downwind of a ridge (lenticular clouds, rotor turbulence).
The ITCZ is a belt of converging trade winds and rising air near the equator; tropical revolving storms need sea temperatures above about 26 to 27 C and enough Coriolis, so none form within about 5 degrees of the equator.
Key numbers, limits and values
ISA MSL: 1013.25 hPa, 15 C (288.15 K), density 1.225 kg/m3.
ISA lapse rate 1.98 C per 1000 ft (rounded to 2), equal to 6.5 C per km.
ISA tropopause: 36,090 ft (11 km), -56.5 C, constant above in the model.
Real tropopause: roughly 16 km over the equator down to about 8 km over the poles verify.
Pressure change near MSL about 1 hPa per 27 ft; the height per hPa increases with altitude.
DALR = 3 C per 1000 ft (about 1 C per 100 m).
SALR about 1.5 C per 1000 ft on average, variable roughly 1.1 to 2.8 depending on temperature and moisture.
Dewpoint lapse for cloud-base estimation: about 2.5 C per 1000 ft difference from the DALR.
Icing is significant roughly between 0 and -40 C, most severe clear/mixed ice around 0 to -20 C verify.
Jet streams sit near the tropopause, roughly FL300 to FL400, cores commonly 60 to 150+ kt, sometimes over 200 kt verify.
Tropical revolving storms develop about 5 to 20 degrees latitude over sea temperatures above 26 to 27 C.
METAR is routine (half-hourly or hourly); SPECI is issued on specified changes; TAF validity is commonly 9, 24 or 30 hours verify.
Formulas and relationships
Convective cloud base (ft AGL) is about (surface T minus surface Td, in C) x 400, i.e. (T minus Td)/2.5 x 1000.
Stability test: ELR less than SALR = absolutely stable; between SALR and DALR = conditionally unstable; greater than DALR = absolutely unstable.
Buys Ballot's Law (Northern Hemisphere): back to the wind, low pressure is on your left, high on your right (reversed in the South).
Thermal wind blows parallel to the thickness lines with cold air to the left in the Northern Hemisphere.
Coriolis force is proportional to wind speed and the sine of latitude, so it is zero at the equator and maximum at the poles.
Temperature error rule of thumb: flying from warm/high pressure into cold/low pressure without correction means true altitude is below indicated.
Mnemonics and memory items
High to Low, Look out Below: into lower pressure or colder air, true altitude is below indicated.
Dry is faster: DALR (3 C/1000 ft) is always greater than SALR (about 1.5), because condensation releases latent heat.
The Earth, great circles, charts and projections, dead reckoning, the compass.
Great circle versus rhumb line (Mercator)
Great circle is the shortest path and cuts each meridian at a changing angle; the rhumb line holds one heading but is longer. They coincide only along the equator or a meridian. Convergency = d.long x sin(mean lat); conversion angle is half of it.
Must-know definitions and concepts
A great circle has its plane through the Earth's centre and is the shortest distance between two points on a sphere.
A rhumb line (loxodrome) crosses every meridian at the same angle; it is not the shortest route except along the equator or a meridian.
Convergency is the angle between two meridians at a given latitude; conversion angle is the angle between the great circle and the rhumb line joining the same two points.
Latitude is 0 to 90 N/S; longitude is 0 to 180 E/W from Greenwich.
1 nautical mile equals 1 minute of arc of latitude; 1 degree of latitude equals 60 nm.
1 minute of longitude equals 1 nm only at the equator, decreasing with cos(latitude).
Departure is the east-west distance in nm between two meridians at a given latitude.
Variation is the angle between true and magnetic north (changes slowly, secular change); deviation is between magnetic and compass north (aircraft-specific, varies with heading).
IAS to CAS to EAS to TAS: instrument/position, then compressibility, then density corrections.
Groundspeed is TAS combined with wind; track is the actual path over the ground.
The triangle of velocities relates the air vector (heading and TAS), the wind, and the ground vector (track and groundspeed).
1-in-60 rule: a 1 degree displacement subtends about 1 nm after 60 nm.
Dead reckoning finds position from heading, TAS, wind and time from a known start; a fix corrects the DR position from external references.
GMT/UTC is based on the Greenwich meridian; LMT is based on the observer's own meridian.
Grid navigation uses a fixed grid north instead of true/magnetic north at high latitudes where meridians converge fast.
Isogonals are lines of equal variation; the agonic line is zero variation. Magnetic dip is 0 at the magnetic equator and 90 at the magnetic poles.
GNSS fixes position by satellite ranging; INS integrates sensed accelerations from a known start and drifts over time.
Key numbers, limits and values
1 international nautical mile = 1852 m exactly, about 6076 ft.
1 degree of latitude = 60 nm; 1 minute of latitude = 1 nm.
Mean radius of the Earth about 3440 nm (6371 km) verify.
Convergency is 0 at the equator and equals the change of longitude at the pole (factor 1 at the pole).
The sun moves 15 degrees of longitude per hour, so 1 degree of longitude = 4 minutes of time.
Lambert standard parallels are typically at about 1/6 and 5/6 of the chart's latitude span verify; scale is correct only along them.
A rhumb line and great circle coincide only along the equator or a meridian.
Mercator scale expands with sec(latitude); it is correct only at the chart's construction latitude (or the equator).
Polar stereographic charts are conformal and can show the pole; a standard Mercator cannot.
TAS rises roughly 2% above CAS per 1000 ft as a quick estimate verify.
A 3 degree glidepath is about 300 ft per nm (a rule of thumb: roughly 100 ft per nm for each degree of glide angle) verify.
Formulas and relationships
Convergency (deg) = change of longitude (deg) x sin(mean latitude).
Conversion angle = 1/2 x convergency.
Departure (nm) = change of longitude (minutes) x cos(latitude).
Difference of latitude (minutes) = distance in nm along a meridian.
1-in-60 rule: angle (deg) is about (distance off track / distance run) x 60.
Radio waves, NDB, VOR, DME, ILS, radar, SSR, GNSS.
ILS: localiser, glide path and markers
Localiser 108.10 to 111.95 MHz (odd first decimals) gives the centreline; glide path 328.6 to 335.4 MHz UHF is auto-paired, nominal 3 degrees. Markers all on 75 MHz: Outer blue low tone, Middle amber medium, Inner white high. Localiser full-scale is about plus or minus 2.5 degrees.
Must-know definitions and concepts
Ground (surface) wave follows the Earth's curvature by diffraction (LF/MF), with greater range over sea than over land; it does not depend on the ionosphere.
Sky wave is refracted back by the ionosphere (mainly HF); range varies with day/night, season and solar activity.
Space (direct) wave is line-of-sight (VHF/UHF/SHF), limited by Earth curvature and height, not the ionosphere.
D layer (daytime only) absorbs MF/HF; its disappearance at night lets sky waves travel much farther. E and F layers reflect HF sky waves; F splits into F1/F2 by day.
Skip distance is the dead zone between the ground-wave limit and where the first sky wave returns.
ADF/NDB: the needle shows Relative Bearing (RB) to the station, clockwise from the nose.
QDM (magnetic bearing to the station) = RB + magnetic heading; QDR (bearing from the station) = QDM plus or minus 180.
VOR reference phase: 30 Hz FM, omnidirectional, constant everywhere. VOR variable phase: 30 Hz AM, its phase changes with azimuth.
A VOR radial is the phase difference, read as the magnetic bearing from the station. The cone of confusion is unreliable indications directly overhead.
DME measures slant range (line of sight), largest error overhead and negligible far out.
ILS: the localiser gives lateral guidance on the extended centreline, the glide path gives vertical guidance at nominally 3 degrees; marker beacons cross the approach at set points.
SSR Mode S assigns a unique 24-bit address for selective interrogation and data link, reducing garbling versus Mode A/C.
RNAV allows any desired path within coverage; RNP adds onboard performance monitoring and alerting; PBN is the ICAO framework of numbered specifications.
WGS-84 is the geodetic datum in which GPS positions are expressed.
Key numbers, limits and values
Speed of radio waves c = 300,000,000 m/s (3 x 10^8).
Bands: VLF 3 to 30 kHz, LF 30 to 300 kHz, MF 300 to 3000 kHz, HF 3 to 30 MHz, VHF 30 to 300 MHz, UHF 300 to 3000 MHz, SHF 3 to 30 GHz.
NDB operates in LF/MF, roughly 190 to 1750 kHz verify.
VOR band 108.00 to 117.95 MHz, 50 kHz spacing; 108.00 to 111.95 shared with the ILS localiser.
ILS localiser 108.10 to 111.95 MHz on odd first-decimal channels; glide slope UHF 328.6 to 335.4 MHz, auto-paired to the localiser.
DME UHF 962 to 1213 MHz, auto-paired to the VOR/ILS.
Marker beacons all on 75 MHz: Outer blue low tone, Middle amber medium tone, Inner white high tone.
SSR: interrogation 1030 MHz, reply 1090 MHz. Radio altimeter 4200 to 4400 MHz (SHF, frequency modulated continuous wave).
Nominal ILS glide path 3 degrees (about 2.5 to 3.5 depending on airfield).
CDI full-scale: VOR plus or minus 10 degrees (each dot about 2), ILS localiser plus or minus 2.5 degrees.
VOR aggregate accuracy about plus or minus 5 degrees; DME accuracy about the better of 0.5 nm or 3% of range verify.
Transponder codes: 7700 emergency, 7600 comms failure, 7500 hijack, 7000 VFR conspicuity (Europe), 2000 entering radar with no assigned code.
ILS minima by category: CAT I DH 200 ft or above, RVR 550 m or above; CAT II DH 100 to 200 ft, RVR 300 m or above; CAT IIIA DH under 100 ft, RVR 200 m or above; CAT IIIB DH under 50 ft, RVR down to about 50 to 75 m verify.
GPS: nominally 24 satellites, 6 planes, about 20,200 km, period about 12 hours verify. A 3D fix needs 4 satellites (3 gives 2D if altitude is known).
RAIM: 5 satellites to detect a fault, 6 to exclude it.
Formulas and relationships
Wavelength (m) = c / f; shortcut wavelength (m) is about 300 / f(MHz).
QDM (to the station) = Relative Bearing + Magnetic Heading (plus or minus 360 as needed).
QDR (from the station) = QDM plus or minus 180.
Radar range R = (c x t) / 2, t = total there-and-back time.
Ground range = sqrt(slant range^2 minus height^2), same units.
VHF/UHF line-of-sight horizon (nm) is about 1.23 x sqrt(height in ft); add both stations' terms for two heights verify.
Mnemonics and memory items
RB + MH = MB: Relative Bearing plus Magnetic Heading gives the bearing to the station (watch the 360 wrap).
A radial is always FROM the station, never to it.
VOR: Reference is Fixed (FM), Variable is AM.
Localiser channels have an odd first decimal (108.10, 108.30); even tenths are VOR.
Marker colour and tone step up toward the runway: blue-low, amber-medium, white-high.
GPS segments: Space, Control, User (who transmits, who manages, who uses). RAIM: 5 to detect, 6 to correct.
Common exam traps
Lower frequency gives longer ground-wave range, and it is greater over sea than land.
Night effect on the NDB is worst around dawn and dusk, when sky and ground waves interfere.
Coastal refraction is zero when the path crosses the coast at 90 degrees and grows at oblique angles.
Quadrantal error is maximum on the 045/135/225/315 relative bearings, zero on the cardinals.
The cone of confusion (overhead geometry) is not the same as the VOR aggregate accuracy figure.
DME slant range error is largest close in/overhead and negligible when range is much greater than height.
The DME channel is auto-paired with the VOR/ILS, not tuned separately.
Mode C reports pressure altitude on 1013.25, not QNH; ATC applies the correction.
A GPS 3D fix needs 4 satellites; 3 gives only a 2D fix if altitude is known.
RAIM depends on satellite geometry as well as count.
The 3 degree glide path is nominal, not universal.
Do not mix up marker beacon colour/tone/pattern between Outer, Middle and Inner.
Treat the CAT I/II/III minima as reference points; exact operational minima vary by aircraft, runway and approval.
Exam figures from the SkyStudy question bank
Two of the 369 code-drawn study figures inside the SkyStudy question bank. Try them with the free demo at skystudyatpl.com/demo.
Ops documents, dangerous goods, low-visibility ops, wake turbulence, MEL.
The 9 dangerous goods classes
The numeric order is the exam-testable sequence. Class 9 (miscellaneous) includes lithium batteries, dry ice and magnetised material. The NOTOC informs the commander of all dangerous goods loaded.
Must-know definitions and concepts
The operator holds primary responsibility for safe operation; the commander has final authority in flight and may deviate from any procedure in an emergency.
The Operations Manual has Parts A (general), B (aircraft operating), C (route/aerodrome) and D (training).
Aerodrome operating minima (RVR/visibility and cloud base) depend on runway facilities, approach category and aircraft category.
Aircraft category A/B/C/D (based on Vat, the reference landing speed) sets the applicable minima and protected airspace.
Low Visibility Operations (LVO) cover takeoff and approach/landing below standard CAT I, needing Low Visibility Procedures (LVP), training and approval.
Clean aircraft: no takeoff with frost, ice or snow adhering to critical surfaces.
Holdover time (HOT) is the estimated time anti-icing fluid protects surfaces, given as a range; a pre-takeoff check confirms whether protection has run out.
MEL is the operator's list of equipment that may be inoperative for dispatch; it can never be less restrictive than the manufacturer's MMEL.
CDL (Configuration Deviation List) permits dispatch with certain external parts missing, usually with a performance penalty.
NOTOC notifies the commander of all dangerous goods loaded.
Decompression is explosive, rapid or gradual by rate of pressure loss; the crew response depends on the classification.
Wake turbulence categories by maximum takeoff mass: Light, Medium, Heavy, Super (the A380 is the classic Super).
ETOPS/EDTO governs operations beyond a set single-engine diversion time from an adequate aerodrome, needing specific approval and planning.
A contaminated runway has more than 25% of the assessed surface covered by water, slush, snow, ice or frost.
Noise abatement departures (NADP 1 and NADP 2) reduce noise near airports while staying safe.
Fuel jettison reduces mass below max landing mass before an emergency landing; not all types are fitted for it.
Volcanic ash is a serious hazard (engine flameout, airframe, systems); operators must avoid it and exit if encountered.
Key numbers, limits and values
90-second rule: certification must show all occupants can evacuate through half the exits, in darkness, within 90 seconds.
MEL rectification categories (letters and order are standard; day counts vary, verify): A per the MEL condition; B within 3 days; C within 10 days; D within 120 days (excluding the day of discovery).
Wake turbulence separation grows when a lighter category follows a heavier one; the largest gap is Light behind Super/Heavy verify.
CAT I is generally to about 200 ft DH and 550 m RVRverify; CAT II/III progressively reduce DH and RVR, CAT IIIB allows very low or no DH and very low RVR.
Normal cabin altitude around 6,000 to 8,000 ft; cabin altitude warning around 10,000 ft verify.
Contaminated runway threshold: more than 25% of the assessed surface covered.
Mnemonics and memory items
Learn the 9 DG classes by number (1 to 9); the numeric order is the exam-testable sequence.
TCAS RA: comply, do not delay, do not fight it; the RA overrides the ATC clearance.
Wake turbulence size order: Super, Heavy, Medium, Light (the bigger they are, the more they stir).
MEL A to D runs from most urgent (A, no fixed limit) to least urgent (D, longest interval).
Low Vis = less freedom, more procedure: protected areas, extra spacing and low-vis taxi routes all activate together.
HOT tells you when to worry, not when it is safe: always pair it with a pre-takeoff check.
Common exam traps
Do not confuse MEL (inoperative systems) with CDL (missing external parts, usually with a performance penalty).
MEL categories are binding limits, not commander discretion, except in a genuine emergency.
A TA is advisory; an RA requires an immediate manoeuvre and takes priority over ATC.
Holdover time is a statistical range, not a guarantee; a pre-takeoff check can still be required within it.
The 90-second rule is a certification demonstration (half the exits blocked), not a guaranteed real-world outcome.
Explosive decompression is under a second from a large opening; rapid is slower but still fast; do not swap them.
Wake separation also applies to Medium behind Heavy/Super, not only Light categories.
LVO applies to both takeoff and landing, not just approach minima.
EDTO terminology now extends the ETOPS concept to some aircraft with more than two engines.
Dangerous goods also cover passenger and crew items (spare lithium batteries), not only cargo.
Volcanic ash also abrades windscreens and blocks pitot/static, not only engines.
A contaminated runway is a distinct, more severe category than merely wet, with different performance calculations.
Exam figures from the SkyStudy question bank
Two of the 369 code-drawn study figures inside the SkyStudy question bank. Try them with the free demo at skystudyatpl.com/demo.
Lift and drag, the stall, stability and control, high-speed flight, propellers.
The drag curve and Vmd
Induced drag falls with speed, parasite drag rises with speed; total drag is a U-shape with its minimum at Vmd (L/Dmax). Vmd is best glide and propeller max range; a jet's max range is faster, around 1.3 x Vmd.
Must-know definitions and concepts
Chord line joins the leading and trailing edges; camber is the curvature relative to the chord.
Angle of attack (AoA) is between the chord and the relative airflow, not the horizon; angle of incidence is the fixed rigged angle to the longitudinal axis.
Relative airflow is parallel to and opposite the flight path.
Aspect ratio = span^2 / area; high aspect ratio gives lower induced drag at the cost of weight and roll rate.
Centre of pressure moves forward as AoA increases, then snaps aft right at the stall; the aerodynamic centre (near quarter chord subsonically) keeps a constant pitching moment instead.
The lift/AoA curve rises nearly linearly to CLmax at the critical AoA, then falls sharply.
Boundary layer: the thin layer slowed by viscosity; laminar (low friction, separates early) or turbulent (higher friction, resists separation).
Flow separation is the boundary layer breaking away: the physical mechanism of the stall.
Downwash and wingtip vortices (high pressure curling to low pressure at the tip) are the source of induced drag.
Washout: decreasing incidence toward the tip so the root stalls first, keeping the ailerons effective.
Ground effect: reduced induced drag and downwash within about one wingspan of the surface, causing float and a lower stall speed.
Static stability is the initial tendency to return to trim; dynamic stability is the response over time (damped, neutral, divergent).
Directional (weathercock) stability from the fin; lateral (dihedral) stability from dihedral, sweep and wing position.
Dutch roll: a yaw/roll oscillation when lateral stability is strong relative to directional (damped by a yaw damper). Spiral instability: a slow diverging bank when directional stability is strong relative to lateral.
Adverse yaw: the down-going aileron makes more induced drag, yawing toward the outside of the turn.
Primary controls (ailerons, elevator, rudder) act about the three axes; secondary/high-lift devices are flaps, slats, trim tabs, spoilers and speed brakes.
Mass balance puts weight ahead of the hinge to prevent flutter; aerodynamic balance reduces pilot control forces (a different purpose).
Mach number = TAS / local speed of sound; a shockwave decelerates flow from supersonic to subsonic with a sudden pressure rise and wave drag.
Buffet is airframe vibration from separated or shock-disturbed flow, at low speed (stall) or high speed (Mach).
Feathering aligns the propeller blades with the airflow to stop windmilling; a constant-speed prop varies blade angle to hold RPM.
Key numbers, limits and values
Critical (stalling) AoA about 15 to 16 degrees for a typical subsonic aerofoil verify.
CLmax occurs at the critical AoA; the critical AoA is constant regardless of weight, altitude, bank or airspeed, only the IAS at which it is reached changes.
CS-25 large-aeroplane limit load factors: +2.5 g to -1.0 g.
CS-23 utility about +4.4 g / -1.76 g; aerobatic about +6 g / -3 gverify.
Va (manoeuvring) is the max speed for a single full control input without exceeding the limit load factor; Va decreases as weight decreases.
Vne never-exceed (red line); Vno max structural cruising (top of the green arc); Vfe max flap extended (top of the white arc).
Mcrit is the free-stream Mach at which airflow first becomes locally sonic somewhere on the airframe.
Coffin corner is where the low-speed stall buffet and high-speed Mach buffet boundaries converge at altitude.
Trailing-edge flaps mainly increase CLmax and drag with little change in critical AoA; slats and slots increase both CLmax and the critical AoA.
Gust loads add to manoeuvre loads and increase with airspeed, hence rough-air penetration speeds.
Formulas and relationships
Lift L = CL x 1/2 x rho x V^2 x S; Drag D = CD x 1/2 x rho x V^2 x S.
Aspect ratio = span^2 / S.
Load factor in a level turn n = L/W = 1/cos(bank angle).
Stall speed Vs is proportional to sqrt(weight / CLmax).
Stall speed in a turn Vs(turn) = Vs(1g) x sqrt(n); a 60 degree bank gives n = 2, so Vs rises about 1.41 times.
Induced drag is proportional to 1/V^2 (dominates at low speed) and to weight^2 at a given speed.
Parasite drag is proportional to V^2 (dominates at high speed); minimum total drag is at Vmd where induced = parasite.
L/Dmax is at Vmd: best glide angle for any aircraft, and the maximum-range speed for a propeller aircraft. A jet at Vmd is at maximum endurance; jet maximum range is faster, about 1.3 x Vmd verify.
Mnemonics and memory items
Camber curves, chord is straight.
AoA moves with the flight path; incidence is bolted to the airframe.
Coffin corner squeezes from both ends: stall buffet speed rises with altitude, Mach buffet speed falls.
Adverse yaw: down aileron drags the nose to the outside of the turn.
Static asks IF it returns to trim; dynamic asks HOW (damped, neutral, divergent).
Dutch roll = too much dihedral for the fin; spiral = too much fin for the dihedral.
Forward CG: more stable, higher stick forces, higher stall speed, more trim drag. Aft CG: less stable, lighter controls, less trim drag, less stall margin.
Mass balance stops flutter; aerodynamic balance lightens the controls.
Common exam traps
Do not confuse AoA (to the relative airflow) with pitch attitude (to the horizon).
Stalling IAS is essentially constant with altitude for a given weight; TAS at the stall rises with altitude, but the critical AoA and CLmax are unchanged.
The critical AoA does not change in a turn; only the IAS to reach it rises with load factor.
Va decreases as weight decreases; do not assume it is fixed or rises when lighter.
Induced drag falls with speed, parasite drag rises; the U-shaped total drag curve has its minimum at Vmd.
Slats/slots increase both CLmax and the critical AoA; plain flaps mainly increase CLmax.
Mach tuck (nose-down from the CP moving aft) is distinct from high-speed Mach buffet (vibration).
Wing sweep delays compressibility by reducing the streamwise flow component; it does not change the aerofoil shape.
Swept wings tend to tip-stall first, countered by fences, vortex generators, saw-tooth edges or washout.
Mass balance (flutter) and aerodynamic balance (control forces) solve different problems.
The area rule (coke-bottle waist) is a transonic wave-drag principle, not a general subsonic rule.
Feathering (blades aligned with the airflow) is not the same as fine/flat pitch (small angle for takeoff RPM).
The +2.5 g / -1.0 g figure is the CS-25 limit; CS-23 utility and aerobatic categories differ.
Exam figures from the SkyStudy question bank
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Phonetic alphabet, standard phraseology, readback, light signals, squawks.
Phonetic alphabet, key numbers and squawks
Numbers are spoken digit by digit (nine is "niner", five is "fife"); a decimal is spoken "decimal". MAYDAY and PAN PAN are each said three times. The three squawks: 7500 hijack, 7600 radio failure, 7700 general emergency.
Must-know definitions and concepts
Readability scale 1 to 5: 1 unreadable, 2 readable now and then, 3 readable with difficulty, 4 readable, 5 perfectly readable.
ROGER = I have received all of your transmission (not agreement or compliance). WILCO = received, understood, will comply.
AFFIRM = yes; NEGATIVE = no / not correct / permission not granted.
STANDBY = wait, I will call you. SAY AGAIN = repeat all or the specified part.
READ BACK = repeat back exactly as received. CORRECTION = an error was made, the correct version follows. DISREGARD = ignore that transmission.
Mandatory readback items: ATC clearances, level instructions, heading and speed instructions, altimeter settings, runway-in-use, SSR codes, and any instruction to enter, hold short of, cross or backtrack a runway.
Callsign abbreviation: only the aircraft callsign may be abbreviated, and only after the station abbreviates it first; never abbreviate the first call to a new station.
Station types: TWR (Aerodrome), APP (Approach), ACC/Control (Area), Information (FIS), Radar, Delivery, Ground, Radio (AFIS).
Report levels as FLIGHT LEVEL (number) above the transition altitude, and as (number) FEET below it.
ATIS is a continuous broadcast of routine aerodrome/met information, coded by a phonetic letter that increments; state the code you received on first contact.
VOLMET is a continuous broadcast of meteorological reports for en-route aircraft.
Distress traffic has absolute priority and imposes silence on the frequency; urgency traffic has priority over all but distress.
Key numbers, limits and values
VHF communication band 118.000 to 136.975 MHz; emergency 121.5 MHz.
8.33 kHz channel spacing is standard in most EASA airspace; the older 25 kHz is being phased out verify.
MAYDAY and PAN PAN are each spoken three times at the start of the call.
Transponder codes: 7500 hijack, 7600 radio failure, 7700 general emergency; 7000 is the common VFR conspicuity squawk verify.
Numbers are spoken digit by digit, except whole hundreds and thousands use HUNDRED and THOUSAND (4500 = four thousand five hundred).
A frequency decimal is spoken as DECIMAL (118.275 = one one eight decimal two seven five).
Time is UTC, normally passed as minutes only (two figures); the full four-figure group (hours and minutes) is used only when confusion is possible.
Digit 9 is NINER and 5 is FIFE.
Radio failure VFR: squawk 7600, continue in VMC, land at the nearest suitable aerodrome.
Mnemonics and memory items
ROGER = Received, WILCO = Will Comply: ROGER never acknowledges an instruction needing compliance.
MAYDAY = grave danger now; PAN PAN = a problem, not yet grave.
Do not confuse ROGER (received) with WILCO (will comply).
Light signals differ in flight versus on the ground. In flight: steady green = cleared to land, flashing green = return to land, steady red = give way and circle, flashing red = do not land. On the ground: steady green = cleared for takeoff, flashing green = cleared to taxi, steady red = stop, flashing red = taxi clear of the runway, flashing white = return to starting point.
7600 is radio failure, not the general emergency code (7700).
NEGATIVE answers a yes/no question; it is not a general unable/refuse statement.
Do not abbreviate your own callsign before ATC does.
QNH gives altitude AMSL, QFE gives height above the reference; do not swap them.
READ BACK confirms content received; SAY AGAIN requests a retransmission.
State the current ATIS letter on first contact.
Only the station controlling the distress (or the aircraft in distress) may lift the imposed silence.
STANDBY means wait, not understood-and-will-comply.
Exam figures from the SkyStudy question bank
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IFR clearances, mandatory readback, holding, radio failure, emergencies.
Transition altitude/level and the hold
Below the transition altitude fly altitudes on QNH; above the transition level fly flight levels on 1013. The transition altitude is fixed and published; the transition level is assigned by ATC and moves with pressure. Never level off inside the layer between them.
Must-know definitions and concepts
An IFR clearance authorises proceeding under specified traffic conditions; it is not an instruction to fly a specific track unless a route is stated.
Items read back verbatim: route clearances, any runway entry/land/takeoff/hold-short/cross/backtrack instruction, runway-in-use, altimeter settings, SSR codes, level, heading and speed instructions, frequency changes, and VDF information.
A conditional clearance is issued and read back as: identification, then the condition, then the clearance.
Transition altitude is fixed and published (QNH); transition level is the lowest usable FL above it on 1013.2 and is assigned by ATC; do not level in the layer between.
RVSM applies FL290 to FL410 inclusive and needs specific approval.
MAYDAY = distress (grave, imminent danger); PAN PAN = urgency (a concern, no immediate danger). PAN can be upgraded to MAYDAY; it is a distinct category, not an automatic step.
SELCAL lets a station call a specific aircraft by a unique tone code, relieving a continuous listening watch.
CPDLC is text-based data link for clearances, complementing voice, especially oceanic/en-route.
MONITOR = listen out on a frequency (no two-way needed); CONTACT = establish two-way communication.
Radio failure IFR, in order of priority: fly the last acknowledged clearance, then the notified or expected further clearance, then the filed flight plan route.
Holding uses standard right turns unless the chart or ATC specifies left; fly the published or amended missed approach if a landing is not completed.
Key numbers, limits and values
CLEARED = authorised to proceed; CLIMB/DESCEND = commence to the level; MAINTAIN = continue at the stated level/speed/heading.
EXPECT = planning information only, not an authorisation to act.
Transponder codes: 7500 hijack, 7600 radio failure, 7700 general emergency.
EASA ATPL exams have no negative markingverify, so never leave a blank. A guess after eliminating two options is a coin flip you paid for.
2. Budget the clock
Divide the minutes by the questions before you start. Anything eating more than about 90 seconds, flag it and move on; unanswered easy questions at the end cost the most.
3. Read the stem twice
Watch for NOT and except, for "most correct", and for unit switches: kg vs lb, nm vs km, hPa vs inHg, ft vs m. Half the classic traps are in the wording, not the theory.
4. Eliminate first
Cross out the two clearly wrong options before comparing the last two. Most distractors are built from the right numbers in the wrong place.
5. The night before
Sleep beats cramming. Skim only the Traps boxes and your flagged weak areas, then stop. Fatigue loses more marks than any single forgotten number.
6. Check the flags
Leave the last minutes to revisit flagged questions and to confirm you answered every question. Change an answer only when you can say why the first one is wrong.
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