AMC1 27.903(d) Engines

ENGINE RESTART CAPABILITY

This AMC replaces FAA AC 27-1B, § AC 27.903B and should be used when demonstrating compliance with CS 27.903(d).

(a)     Explanation

CS 27.903(d) requires that any engine must have a restart capability that has been demonstrated throughout a flight envelope to be certificated for the rotorcraft.

(b)     Procedures

Compliance is usually demonstrated by conducting actual in-flight restarts during flight tests or other tests in accordance with an approved test plan. However, CS 27.903(d)(1) does not require in-flight demonstration of restart capability for single-engine rotorcraft or for all-engine shutdown of multi-engine rotorcraft. In the past, engine restart capability for single-engine rotorcraft has been demonstrated on the ground taking into account altitude effects, warm engine characteristics, depleted battery, etc. Restarts should be conducted at various altitudes, ambient temperatures, and fuel temperatures using the most critical fuel type unless the applicant can show that this parameter is not pertinent. Latest-technology engines embody electronic engine controls (EEC or FADEC) that may have sophisticated starting or restarting laws. For these designs the engine restart capability demonstrated on ground may not provide an appropriate level of representativeness required and therefore applicants are encouraged to demonstrate the capability in flight.

The pilot station arrangement for flight controls and engine starting controls should be assessed in the context of an engine restart operation. It should be verified that the engine restart can be accomplished without jeopardising continued safe operation of the rotorcraft. Pilot workload for a pre-existing one engine inoperative (OEI) situation, the location of the restart system controls, and the availability of a second pilot should be considered. The emergency and malfunction instruction sections of the RFM should present a detailed definition of the approved restart envelope and detailed instructions for the restart.

Eligible ambient atmospheric conditions, pre-start requirements (to allow for waste fuel drainage), starter duty cycle (if different from the ground start duty cycle), and pre-start situation analysis should be included. The pre-start situation analysis should consider the following questions:

(1)     Should a restart be attempted in view of the cause of the initial shutdown?

(2)     Is the inlet system ice ingestion a possibility?

(3)     Is re-ignition of fuel in the engine nacelle a possibility?

(4)     Is sufficient restart time available?

(5)     Is power available?

(6)     Is altitude sufficient to maintain terrain clearance?

Windmilling of the engine can be considered to be part of this restart capability; however, most rotorcraft airspeeds and engine locations do not support engine windmilling up to start speeds. Only electrical power requirements were considered for restarting; however, other factors that may affect this capability are permitted to be considered. Engine restart capability following an in-flight shutdown of all engines is the primary requirement, and the means of providing this capability is left to the applicant.

To minimise any potential altitude loss, the applicant should ensure that the engine restart can be initiated at the earliest opportunity. The engine certification should be checked to ensure that the flight manual procedures for in-flight restart are consistent with any specific engine restart requirements identified in the installation and/or operating manual of the engine. If the procedure was only demonstrated on ground, this should be stated in the RFM.

[Amdt 27/10]