Instruments, Warning Systems and Avionics

Instruments are the crew’s senses, and they share sources. The pitot-static block feeds airspeed, altimeter and vertical speed indication from one set of ports and one set of lines, so a single blocked static port makes all three disagree with the aircraft’s actual state — and a blocked pitot with an open static port makes the airspeed indicator over-read in a climb. Leak-check the system after any line is opened and any port is handled.

Gyroscopic indications for attitude, heading and turn rate are driven by vacuum or electric gyros, and failure is usually announced by a flag or a warning rather than by a gradual drift. Engine indications — tachometer, manifold pressure, exhaust gas temperature, cylinder head temperature, fuel flow and oil pressure — are the primary condition monitoring instruments, and their limits come from the engine manual.

Position and warning systems, including gear indication, takeoff configuration warning, stall warning and terrain awareness, are tested to schedule because a silent warning is worse than none. Emergency locator transmitters are tested at their published interval and their identity code is recorded.

Avionics installations are governed by electromagnetic interference, antenna placement and pattern, bonding and grounding, and approved software configuration. Troubleshoot from the sensor inward — ports, lines, wiring, then the unit — and never replace a box before the upstream wiring and connectors are proven.