CAAB AME B2 Exam common mistakes
CAAB AME B2 Exam · Understand the traps and how to avoid them.
When converting prefixed SI units, the candidate applies the prefix factor once instead of raising it to the power of the unit - e.g. writes 1 mm² = 1 × 10⁻³ m², or converts kPa to N/m² by moving the decimal three places but forgets the square in an area-based formula.
The prefix table (milli = 10⁻³) is memorised as a linear scale, and under time pressure the candidate converts the number that is visible in the stem rather than the physical quantity, then picks the multiple-choice option whose digits match.
What to do instead
Convert every quantity to base SI units on paper before substituting, and write the factor with its exponent explicitly: 1 mm² = (10⁻³ m)² = 10⁻⁶ m², 1 mm³ = 10⁻⁹ m³, 1 kPa = 10³ N/m². Sanity-check the magnitude (a 1 m² area cannot contain only 1000 mm²).
In hydraulic press / piston problems the candidate substitutes the given diameters directly into a force ratio (F₁/F₂ = d₁/d₂) instead of converting to areas first.
The question stem supplies diameters, and calculating A = πd²/4 for both pistons adds two arithmetic steps that feel unnecessary when an answer option matches the simple diameter ratio.
What to do instead
Always compute both areas before forming any ratio, then apply F₁/A₁ = F₂/A₂. Remember that force and travel ratios scale with the square of the diameter, so a 3:1 diameter ratio gives a 9:1 force ratio, never 3:1.
Uses peak voltage in power and heating calculations (P = V²/R, I²R) instead of RMS voltage, or reports a peak value when the question asks for the value an AC meter would indicate.
The peak value is the number that appears in the waveform diagram or statement, and the √2 factor is easily dropped when the arithmetic looks tidy without it.
What to do instead
Fix the rule in memory: RMS is the heating-equivalent (DC-equivalent) value, V_rms = V_peak/√2 = 0.707 V_peak, I_rms = I_peak/√2. Use RMS for power, meter readings and cable rating; use peak only for insulation/breakdown and waveform description.
States the gain of the inverting op-amp configuration as positive Rf/Rin, or gives the non-inverting configuration a gain of Rf/Rin without the '1 +' term.
Both configurations use the same two resistors, so the formulas are memorised as one magnitude and the sign/offset detail is lost; the candidate then selects by pattern-matching the resistor ratio.
What to do instead
Re-derive from the virtual-earth assumption: inverting input held at 0 V, so gain = −Rf/Rin (signal inverted); non-inverting input, so gain = 1 + Rf/Rin (never less than unity). Sketch the input terminal each time before answering.
Makes off-by-one errors in digital number work - e.g. treating 2⁸ = 256 as the largest 8-bit value instead of 255, or computing converter resolution from 2ⁿ when the question uses 2ⁿ − 1 levels.
The exponent rule (2ⁿ total states) is well known but the distinction between 'number of levels' and 'maximum value' is not, so the two are used interchangeably.
What to do instead
Write both facts explicitly before answering: an n-bit word has 2ⁿ distinct levels, numbered 0 to 2ⁿ − 1, so 8 bits gives 0–255 (256 codes). For a converter, LSB = V_ref/2ⁿ and full-scale reading corresponds to code 2ⁿ − 1.
Claims that aluminium alloys are hardened by quenching alone, or uses 'annealing' and 'solution treatment' as synonyms when describing heat treatment of a precipitation-hardening alloy.
The steel model (heat and quench = hard) is learned first and carried across to aluminium; quench and age both appear in aluminium descriptions, so the two stages blur.
What to do instead
Keep the two-stage aluminium sequence separate: solution treatment (soak to dissolve alloying elements) + rapid quench gives a supersaturated, relatively soft condition; hardening then comes from natural or artificial ageing (e.g. T6) which precipitates the alloying elements. Annealing is the opposite process - softening by controlled cooling.
Leaves a calibrated micrometer-type torque wrench set at its working value when returning it to the rack, or uses a torque wrench to loosen a seized fastener.
The tool is treated as a general-purpose bar, and storing it 'ready for next time' feels efficient rather than damaging.
What to do instead
Loosen with a breaker bar - a torque wrench is a measuring instrument and must never be used to break a fastener free. After use, wind the micrometer setting back to its lowest value so the spring is unloaded, then confirm the calibration label is in date before the next task.
Treats lift as directly proportional to airspeed (double the speed, double the lift) rather than to the square of airspeed, and/or measures angle of attack from the aircraft's pitch attitude.
Lift is quoted as 'increasing with speed' in qualitative explanations, and in level flight a small pitch change and a small AoA change happen together, so the two angles appear interchangeable.
What to do instead
Use L = ½ρV²SC_L: lift varies with the square of TAS at constant C_L, so doubling speed quadruples lift and halving it leaves a quarter. Define AoA strictly as the angle between the wing chord line and the relative airflow - pitch attitude is the fuselage reference line against the horizon and can differ from AoA.
Classifies every unintended action as a 'mistake', for example calling the wrong switch selection or a forgotten step in a procedure a mistake or even a violation.
'Mistake' is the everyday word for any error, and the exam's technical taxonomy (slip, lapse, mistake, violation) is not applied unless the intention behind the action is examined first.
What to do instead
Classify by intention and level: slip = correct intention, wrong execution (skill-based, e.g. wrong switch selected); lapse = correct intention, action omitted or forgotten (memory failure); mistake = wrong intention from a rule-based or knowledge-based misjudgement; violation = deliberate deviation from a known rule. Ask 'was the intention correct?' before choosing.
Assumes any licensed engineer may certify any task on any aircraft, ignoring the licence category (B1/B2), the type/task endorsements on the licence, and the scope and approval of the maintenance organisation.
The licence is pictured as a single blanket permission, and multiple-choice stems about certification often contain a plausible-sounding 'the licensed engineer certifies the work' option.
What to do instead
Check three gates in order before answering: does the licence category cover the task (B1 mechanical/airframe-engine, B2 avionics/electrical systems)? Is the aircraft type endorsed on the licence? Is the task within the approved organisation's scope and capability? Also separate individual certification (line) from the organisation's Certificate of Release to Service after base maintenance.