Aircraft General Knowledge: Instrumentation
Instrumentation questions test whether you understand what a sensor measures, how it is displayed, and how it fails. Group your knowledge into pitot-static, gyroscopic, magnetic, and engine/aircraft systems instrumentation.
Pitot-static: the airspeed indicator compares pitot (total) pressure with static pressure; the altimeter and VSI respond to static pressure only. Understand position error, compressibility error, density error, and the difference between IAS, CAS, EAS and TAS. Know the altimeter's three-pointer or drum presentation and the risk of misreading. Gyroscopics: rigidity and precession; attitude and heading indicators are earth-referenced, rate-of-turn indicators are not. Understand apparent wander, real wander and transport wander, and why slaving to a flux valve corrects heading drift. Magnetic: variation versus deviation, and turning/dip errors. Modern displays: ADIRU/IRS alignment, air data computers, EFIS colour conventions and the meaning of red, amber, green and white. Engine instruments: EGT/ITT, torque, RPM, fuel flow and their limits.
Traps: thinking the VSI responds to pitot pressure; confusing variation (geographic) with deviation (aircraft); and assuming an EFIS warning colour indicates the same urgency in every manufacturer's design - answer from the stated convention.
Worked example: an aircraft climbs at constant IAS with no altimeter change. Static pressure is blocked, so the altimeter and VSI freeze while the ASI continues to respond to pitot pressure. Rule of thumb: blocked static = ASI over-reads in climb, under-reads in descent; blocked pitot = ASI behaves like an altimeter.