Aircraft Systems, Powerplants, and Flight Instruments
Systems you must be able to troubleshoot on paper
Split the aircraft into four teaching blocks: electrical, pitot-static, gyroscopic, and powerplant/fuel.
Pitot-static. The airspeed indicator, altimeter, and VSI all use the static port. Block the static source and the altimeter freezes; opening the alternate static source, which is inside a pressurized cabin, gives slightly lower pressure than actual, so the altimeter reads high and the airspeed reads high. Block the pitot tube only (drain open) and the airspeed indicator acts like an altimeter: climbs show increasing airspeed.
Gyros. Heading and attitude indicators are typically vacuum driven on training aircraft; the turn coordinator is electric. A vacuum failure leaves you with the turn coordinator and magnetic compass. Rigidity and precession explain the instruments.
Compass. Variation (earth's field) and deviation (aircraft's own field) both must be applied. Remember ANDS: accelerate north, turn south.
Powerplant. Carburetor ice forms at 20–70°F with high humidity and shows as a slow RPM drop - apply carb heat. Detonation is uncontrolled explosion after ignition; preignition is ignition before the spark. A constant-speed propeller's governor changes blade angle to hold RPM, driven by engine oil pressure.
Trap: calling the airspeed indicator a gyro instrument, or assuming an attitude indicator will survive a vacuum failure.
Worked example: Pitot blocked, drain open. Climb 2,000 ft → indicated airspeed rises. Descend → it falls.