Abstract: A maintenance interval indication system, apparatus and method are provided that are cost-effective for general aviation aircraft and that may be retrofitted to existing airplanes. The system includes an on-board aircraft cycle counter and engine run-time and flight time logging instrument that requires no external transducers, no electrical signal inputs and only a single electrical power input from an airframe's electrical system. A microprocessor in the engine cycle logger accepts data input from an acoustic transducer and from a pressure transducer (i.e., altimeter), and correctly logs engine cycles in spite of factors such as: a) touch-and-go landings; b) in-flight engine shutdowns; c) noise from another engine on the same aircraft: d) wide variations in acoustic input levels from one engine to the next; e) changes in acoustic level following an overhaul of the monitored engine; f) transient noise artifacts; and g) transient altitude artifacts.

Abstract: An anti-theft system that can be retrofitted onto existing aircraft disables the starter motor of an engine or engines a predetermined time after the aircraft is taken out of service and re-enables starting only after the pilot has provided adequate identification (e.g. by entering a personal identification number at a cockpit keyboard). The predetermined time interval is selected to be long enough to ensure that the system does not impose a flight hazard by preventing in-flight re-starts. In a preferred version of the system, a drop in the output voltage of the aircraft's main electric power system is used as an indication that the aircraft is out of service. To simplify installation on existing aircraft, the system provides for communication among various functional elements over a pre-existing part of the aircraft (e.g. by imposing AC tones on a starter motor control line).