Aircraft Instruments, Systems and Partial-Panel Operations
What this domain tests
Which instrument is driven by which system, what it reads when that system fails, and how to keep control of the aircraft with the instruments that remain.
Two families
The pitot-static group is the airspeed indicator, altimeter and vertical speed indicator. The gyroscopic group is the attitude indicator and heading indicator, normally vacuum or pressure driven, plus the electrically driven turn coordinator. That difference is the whole logic of partial panel: a vacuum failure takes the attitude and heading indicators, and leaves the turn coordinator, ASI, altimeter and VSI as your panel.
Recognising failures
A blocked pitot tube leaves the ASI behaving like an altimeter in the climb and freezing in level flight; the static port is unaffected. A blocked static port makes the ASI over-read in a climb, the VSI freeze at zero, and the altimeter stick at the altitude where the blockage occurred. A vacuum failure shows as a slowly erecting, then tumbling, attitude indicator, with the suction gauge off its normal range. A failed AHRS in a glass cockpit requires reversion to the standby instruments or the backup display.
Worked example
Climbing through FL100 in IMC, the ASI climbs past the normal climb speed while the VSI reads zero and the altimeter stops moving. Reasoning: all three are pitot-static instruments and all three are misbehaving in a way consistent with a blocked static source - ASI over-reading in the climb, VSI frozen, altimeter stuck. Action: select alternate static source if fitted, otherwise level off, reduce power, use GPS altitude and known pitch/power settings, and declare the problem.
Traps
Assuming the turn coordinator provides attitude - it provides rate of turn and, indirectly, bank; assuming a normal suction gauge proves the attitude indicator is healthy; forgetting to cross-check the standby instruments after a glass-panel failure.