Aircraft General Knowledge - Airframe, Systems and Instruments
Airframe, engine and systems
The syllabus covers the aeroplane's structure and flying controls, the four-stroke piston engine (induction, compression, power, exhaust), the dual ignition system with two independent magnetos, the carburettor or fuel-injection unit, mixture control, oil and cooling, and the constant-speed propeller whose blade angle is managed by a governor. You should also know the electrical system, the vacuum- or electrically driven gyroscopes, and the pitot-static system that feeds the ASI, altimeter and VSI.
Instruments and their errors
Learn each instrument with its source and its characteristic error. The ASI suffers position and density error, and with a blocked pitot and open static it behaves like an altimeter. The altimeter reads correctly only when the subscale matches the pressure datum in use: QNH gives elevation, QFE gives height above the reference, standard 1013 gives flight levels. The VSI lags. The direct-reading compass suffers variation, deviation, turning error (it under-reads in a turn through north in the northern hemisphere) and acceleration error - ANDS: accelerate north, decelerate south.
Common traps
Carburettor icing is most likely at low power settings and in descent, not only in visible moisture. A magneto check may fall within the permitted drop yet still be unsatisfactory if the engine runs rough. Questions also confuse indicated altitude with true altitude when pressure changes in flight.
Worked example
You cruise with 1013 set while the regional QNH is 1003. The altimeter over-reads by roughly 10 × 30 = 300 ft, so your true altitude is lower than indicated - 'high to low, look out below'. Reset to QNH before descent.