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.
Rationale: Airlines are increasingly using extended duration transoceanic flights upto ~ 20 hours in their operations. Fleet sizes using ETOPS are growing and the engines in the fleet are aging with natural degradation of performance in terms of thrust capability, surge/stall margins and control response times. Other hardware issues or anomalies can create potential for engine hazardous events.
Significant operational events have occurred in this regard, leading to Airworthiness Directives and significant disruptions/costs for the aviation community. Examples are EASA AD-20200010R2-1 Rolls-Royce Trent 1000 on Boeing 787), FAA AD 2010-09-14 (CFM International CFM56-5 on Airbus A320) and FAA AD 2012-06-18 (Pratt & Whitney PW4000 family of engines on different aircraft models). Published versions of Airworthiness Directives including these and others are available at the FAA/EASA websites. https://www.faa.gov/regulations_policies/airworthiness_directives/ and https://ad.easa.europa.eu/.
An effective system for detecting, prognosticating the propensity for such deterioration or fault precursors, is essential for reducing fleet operational events and disruptions. This should be feasible to a great extent utilizing the advances made by the industry capability of embedded propulsion system models, tracking filters (S. Adibhatla et al) and predictive analytics; alongwith the general increase in computation and data communication capability.
Significant operational events have occurred in this regard, leading to Airworthiness Directives and significant disruptions/costs for the aviation community. Examples are EASA AD-20200010R2-1 Rolls-Royce Trent 1000 on Boeing 787), FAA AD 2010-09-14 (CFM International CFM56-5 on Airbus A320) and FAA AD 2012-06-18 (Pratt & Whitney PW4000 family of engines on different aircraft models). Published versions of Airworthiness Directives including these and others are available at the FAA/EASA websites. https://www.faa.gov/regulations_policies/airworthiness_directives/ and https://ad.easa.europa.eu/.
An effective system for detecting, prognosticating the propensity for such deterioration or fault precursors, is essential for reducing fleet operational events and disruptions. This should be feasible to a great extent utilizing the advances made by the industry capability of embedded propulsion system models, tracking filters (S. Adibhatla et al) and predictive analytics; alongwith the general increase in computation and data communication capability.