GCAA CAR-66 Category A Exam common mistakes
GCAA CAR-66 Category A Exam · Understand the traps and how to avoid them.
Mixing up the order of operations when simplifying expressions such as 2 + 3 × 4², evaluating left to right instead of applying indices, then multiplication/division, then addition/subtraction.
Under exam time pressure candidates fall back on habitual left-to-right reading rather than consciously applying precedence rules, and powers are often expanded incorrectly (e.g. treating 4² as 4 × 2).
What to do instead
Before each calculation write the mnemonic order (BODMAS/PEMDAS) at the top of the working area and explicitly box the index term first; practise 20 mixed-precedence expressions until the sequence is automatic.
Using the wrong trigonometric ratio or forgetting to check the calculator is in degree mode when resolving a force into components or finding an angle in a right triangle.
Candidates memorise SOH-CAH-TOA but mislabel which side is opposite/adjacent relative to the stated angle, and calculators left in radian mode silently give plausible-looking wrong answers.
What to do instead
Sketch the triangle, label the angle and mark the sides O/A/H before choosing the ratio; at the start of every exam session verify the DEG indicator on the calculator display.
Adding or subtracting vectors by simply summing their magnitudes, ignoring direction, when computing a resultant force or velocity.
Scalar arithmetic is more familiar and faster, and candidates under-recognise that forces at an angle require a vector (parallelogram or component) approach.
What to do instead
Whenever a question gives two forces at an angle, immediately resolve each into horizontal and vertical components, sum components, then recombine with Pythagoras and arctan; never add magnitudes unless the vectors are collinear.
Confusing mass with weight, or using g incorrectly (e.g. reporting a 10 kg mass as 10 N, or omitting g entirely in a force/energy calculation).
Everyday language uses 'weight' for mass, and the distinction is only sharpened by repeated practice; candidates also forget g = 9.81 m/s² when the question is in SI units.
What to do instead
Adopt the habit of writing units after every intermediate value and checking dimensional consistency (kg vs N); do a set of problems converting between mass and weight in both directions.
Misapplying Ohm's law or the power formulas in series/parallel networks, for example treating parallel resistors as additive or using total voltage across an individual branch resistor.
Candidates memorise V = IR but not which quantity is common in each configuration (current is common in series, voltage common in parallel), and they rush to plug numbers in without redrawing the circuit.
What to do instead
Redraw the circuit and label the common quantity for each element before calculating; derive total resistance first, find total current, then work back through each branch; verify with the power balance (power supplied = power dissipated).
Reversing the bias condition or the terminal behaviour of a diode/Zener/transistor when interpreting a simple circuit description (e.g. assuming a forward-biased silicon diode drops 0.7 V in the wrong direction, or confusing NPN and PNP base current direction).
The symbolic arrow conventions are easy to memorise visually but hard to recall verbally under exam conditions, and candidates conflate the three operating regions of a transistor.
What to do instead
Learn one canonical rule per device (silicon forward drop ≈ 0.7 V, arrow on emitter points in the direction of conventional current) and redraw the device with its arrow before answering; practise identifying cut-off/active/saturation from stated terminal voltages.
Converting between number bases or interpreting logic levels/truth tables incorrectly, such as reading a binary-coded value with the wrong bit weighting or misidentifying an output from a stated gate combination.
Candidates count bit positions from the left instead of the right, or evaluate a multi-gate circuit in the wrong order, and the abstract nature of the topic means errors are not caught by intuition.
What to do instead
Always write place values (…128, 64, 32, 16, 8, 4, 2, 1) above the bits starting from the right; for logic circuits evaluate innermost gates first and write the intermediate output at each node before proceeding.
Selecting the wrong material or heat-treatment for a stated application (e.g. choosing mild steel where a hardened high-carbon steel is needed, or confusing annealing with hardening when asked how to relieve internal stress).
The property tables are memorised as isolated facts without an application link, so candidates match on a single keyword (e.g. 'strong') rather than the full requirement (strength plus ductility plus corrosion resistance).
What to do instead
Build a one-page comparison table of common aircraft materials (2024, 7075, 4130, titanium, composites) listing strength, corrosion behaviour, and typical use; for each exam question name the dominant requirement first, then match the material to it.
Omitting or misapplying torque values, safetying, and lockwire/FOD precautions when answering maintenance-practice questions, or describing a procedure out of its correct sequence.
Candidates answer from general workshop intuition rather than from the disciplined procedural sequence, and they under-weight the 'prevent recurrence' step in fault-finding questions.
What to do instead
For every procedure question, mentally rehearse the full sequence (prepare/isolate, inspect, rectify to the manual, torque to specification, secure/lock, record, clear FOD) and check the answer against each stage before committing.
Confusing the four forces and their balance in different flight phases, or mis-stating how angle of attack, camber, and speed affect lift and the stall (e.g. claiming a stall depends primarily on airspeed rather than exceeding the critical angle of attack).
Everyday explanations ('stall speed') reinforce the airspeed misconception, and candidates conflate the effects of changing speed with changing angle of attack.
What to do instead
Anchor on the principle that lift depends on angle of attack and dynamic pressure, and that a stall occurs at the critical angle of attack at any speed, weight, or attitude; work through one worked example per flight phase (level, climb, descent, turn) balancing the four forces.
Treating human-factors questions as common sense and selecting the 'obvious' answer, ignoring the formal concepts of error types (slips, lapses, mistakes, violations) and the SHELL/Reason model terminology.
The domain feels intuitive, so candidates do not study the defined vocabulary and cannot distinguish, for example, a skill-based slip from a decision-based mistake.
What to do instead
Learn the definitions with one concrete aviation example each, and classify every practice scenario explicitly by error type and by the model layer (liveware–software, liveware–liveware, etc.) before choosing an option.
Mixing up the roles, validity periods, and privileges of licences, ratings, and certificates (e.g. confusing a Type Rating with a licence, or mis-stating recency/continuation requirements), or citing the wrong regulatory part for a maintenance task.
The legislation is dense and candidates memorise numbers without linking each to its purpose, so similar-sounding requirements blur together.
What to do instead
Create a structured summary sheet mapping each document/rating to its holder, privilege, validity, and renewal condition, and cross-check every practice question against that sheet until the associations are firm.