MCAA PPL Theory Exam common mistakes
MCAA PPL Theory Exam · Understand the traps and how to avoid them.
Applying the standard atmosphere lapse rate (2°C per 1,000 ft) to the whole troposphere, or using the surface temperature instead of the ISA deviation at the aircraft's level when computing density altitude and true altitude.
The 2°C/1,000 ft figure is only the ISA model; in the real atmosphere the actual lapse rate differs, and candidates memorise the number without separating 'temperature at the level' from 'temperature at the aerodrome'. They also forget that true altitude is higher than indicated when the air is warmer than ISA and lower when colder.
What to do instead
Work every problem in a fixed sequence: pressure altitude = indicated altitude ± (QNH − 1013) × 30 ft; then find ISA temperature at that pressure altitude; then deviation = actual − ISA; then true altitude correction ≈ 4 ft per 1,000 ft per 1°C of deviation, added when warm. Practise ten mixed warm/cold cases until the sign of the correction is automatic.
Mixing up the definitions and use of QNH, QFE and QNE, e.g. setting QFE for the cruise, or believing the altimeter reads aerodrome elevation with QFE set.
The three subscale settings look interchangeable on a checklist and candidates learn them as 'aerodrome pressure' without linking each to the altitude it displays and the transition altitude rules that govern when to change.
What to do instead
Anchor each to one sentence you can recite: QNH → altimeter reads elevation above mean sea level; QFE → reads height above the reference datum (usually the aerodrome); QNE/standard 1013.25 → reads pressure altitude, used above the transition altitude. Then draw the transition altitude/level diagram and state which setting is used either side of it.
Answering loading questions by adding masses and comparing with MTOM only, ignoring that the CG position must also fall inside the forward and aft limits at take-off, in flight and at landing.
Candidates treat mass and balance as a single 'am I overweight?' check and skip the moment/arm arithmetic, or they forget that fuel burn moves the CG and that zero-fuel mass has its own limit.
What to do instead
Always build a full table: item, mass, arm, moment; sum moments and divide by total mass to get the CG arm, then convert to %MAC if required. Check four conditions every time: MTOM, MZFM, and CG within limits for take-off and landing. Do one complete worked example per session so the arithmetic stays fluent under time pressure.
Using the magnetic variation with the wrong sign when converting between true and magnetic, and confusing variation (stationary, chart-based) with deviation (aircraft-specific, from the compass card).
The rhyme-based memory aids are easily reversed, and the two corrections are taught together, so candidates apply a compass deviation to a chart heading or add variation in the wrong direction.
What to do instead
Write the relationship explicitly: magnetic = true ± variation (east subtract, west add when going true→magnetic); compass = magnetic ± deviation. Then do a three-step drill: chart true course → apply variation → apply deviation from the card → check against the actual compass reading. Never use deviation outside the aircraft.
Calculating a crosswind component by using the full wind speed, or taking the headwind component as the wind speed, when the wind is at an angle to the runway.
The mental 'clock' method is remembered as a rough guess rather than a sine/cosine relationship, and candidates misjudge the angle between wind direction and runway heading (often using the reciprocal runway).
What to do instead
First compute the angle between wind direction and runway magnetic heading, then use crosswind = wind speed × sin(angle), headwind = wind speed × cos(angle). Use the clock rule only as a check (15° ≈ ¼, 30° ≈ ½, 45° ≈ ¾, 60°+ ≈ full). Verify you have chosen the runway actually in use before computing.
Treating the four forces in a climb or descent as if thrust and drag act along the flight path with lift equal to weight, instead of resolving along and perpendicular to the flight path.
The straight-and-level diagram is learned first and never revised for the inclined case, so candidates believe lift always equals weight and that thrust always equals drag in a steady climb.
What to do instead
Redraw the force diagram with the flight path inclined: in a steady climb, thrust = drag + weight × sin(climb angle) and lift = weight × cos(climb angle). State this for a steady climb, a steady descent and a level turn (load factor = 1/cos bank angle) until each case is distinct.
Confusing the causes of a stall (exceeding the critical angle of attack) with the factors that change the stalling speed (mass, load factor, power, flap, CG), and answering that a stall occurs at a fixed speed.
Training aircraft stall at similar indicated speeds in similar conditions, which reinforces the false idea that stall speed is a property of the aeroplane rather than of the angle of attack. Candidates also forget the 1g versus accelerated stall distinction.
What to do instead
Memorise one rule: the wing stalls at the critical angle of attack regardless of speed, attitude or weight. Then list how stall speed varies: increases with the square root of load factor (√n) and with mass, decreases with flap and forward CG. Rehearse the level-turn case: at 60° bank, load factor 2, stall speed rises by about 41%.
Reading a METAR or TAF and missing the change groups, the validity period, or the meaning of CAVOK, BECMG, TEMPO and PROB30, then answering about conditions that are only forecast temporarily.
The coded groups are learned as vocabulary rather than as a grammar, so the time element (when a change starts and ends, whether it is temporary or becoming) is skimmed and the answer is taken from the wrong part of the report.
What to do instead
Decode in a fixed order: station and time, wind, visibility, weather, cloud, temperature/dewpoint, QNH, then trend. Highlight BECMG (permanent change within the period), TEMPO (temporary fluctuations), PROB30/PROB40 (probability). For TAF, write the validity period first and place every change group on a timeline before answering.
Answering human performance questions by intuition about 'being tired' rather than applying defined concepts such as hypoxia types, the stages of sleep, or the difference between stress and workload.
The domain feels like common sense, so candidates skip the definitions and rely on everyday meanings, which do not match the technical distinctions the syllabus requires.
What to do instead
Build a one-page glossary of the tested definitions (hypoxic/hypemic/stagnant histotoxic hypoxia, hyperventilation versus hypoxia symptoms, circadian rhythm, sleep debt, the four-stage stress model, situational awareness levels) and test yourself by writing the definition before checking it. Use the definition, not the everyday word, in the answer.
Giving a radio call that omits the required elements, or reading back only part of an ATC clearance, especially the level, heading or frequency.
Candidates rehearse phraseology as a script and, under pressure, transmit the aircraft identification and request but drop the position, level, or the read-back items ATC needs confirmed.
What to do instead
Use the standard order for a position report: station addressed, callsign, position, time, level, next position and ETA. For read-backs, repeat at least the level, heading, speed, frequency and any altimeter setting, then end with the callsign. Practise aloud with a timer so the call fits a normal transmission length.