Browse Standards ARP6835
WIP 2020-04-24

Propulsion System Monitoring for Continued Airworthiness ARP6835

The SAE E-32 Committee is requested to develop standards for Commercial Aircraft Engine Monitoring to support the Continued Airworthiness of aircraft in general, with particular emphasis on the ETOPS (Extended Operations) to support the regulations. 14CFR A33.3 (c) ETOPS Requirements. For an applicant seeking eligibility for an engine to be installed on an airplane approved for ETOPS, the Instructions for Continued Airworthiness must include procedures for engine condition monitoring. The engine condition monitoring procedures must be able to determine prior to flight, whether an engine is capable of providing, within approved engine operating limits, maximum continuous power or thrust, bleed air, and power extraction required for a relevant engine inoperative diversion. For an engine to be installed on a two-engine airplane approved for ETOPS, the engine condition monitoring procedures must be validated before ETOPS eligibility is granted. Sec. 33.28) - Engine control systems (a).. is part of engine type design, that controls, limits, or monitors engine operation, and is necessary for the continued airworthiness of the engine. (b)(ii) Complies with the operability requirements of Sec. Sec. 33.51(Operations Test), 33.65 (Surge & Stall) and 33.73(Transient Response), as appropriate, under all likely system inputs and allowable engine power or thrust demands, unless it can be demonstrated that failure of the control function results in a non-dispatchable condition in the intended application; The Engine/propulsion monitoring system for continued airworthiness needs to indicate : - Significant degradation in engine thrust output capability - Significant degradation in acceleration response time for Takeoff Go-Arounds - Impending potential for engine surge or stall (e.g. engine deterioration/wear, compressor blockage due to sand/dirt, biocide overdose etc) - impending potential for engine hazardous events per 33.75(g)(2)(e.g. high energy debris, combustor burn-thru, fire/overheat, toxic products in bleed air, etc) The monitoring system may be onboard or offboard or combination. It is recognized that there will be variability in accuracy of prognostics and detection. Those should be estimated to the extent feasible. Detailed text of pertinent FAA regulations (33.4, 121.374, 33.28, 33.51, 33.65, 33.73, 33.75, 33.89) is in the attachment. The upcoming AC 43-218 will provide the airlines guidance on getting authorization to use Aircraft/ propulsion monitoring systems.
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