ED Decision 2003/15/RM
(a) For the purpose of this CS-27, the powerplant installation includes each part of the rotorcraft (other than the main and auxiliary rotor structures) that:
(1) Is necessary for propulsion;
(2) Affects the control of the major propulsive units; or
(3) Affects the safety of the major propulsive units between normal inspections or overhauls.
(b) For each powerplant installation:
(1) Each component of the installation must be constructed, arranged, and installed to ensure its continued safe operation between normal inspections or overhauls for the range of temperature and altitude for which approval is requested;
(2) Accessibility must be provided to allow any inspection and maintenance necessary for continued airworthiness;
(3) Electrical interconnections must be provided to prevent differences of potential between major components of the installation and the rest of the rotorcraft;
(4) Axial and radial expansion of turbine engines may not affect the safety of the installation; and
(5) Design precautions must be taken to minimise the possibility of incorrect assembly of components and equipment essential to safe operation of the rotorcraft, except where operation with the incorrect assembly can be shown to be extremely improbable.
(c) The installation must comply with:
(1) The installation instructions provided under CS-E; and
(2) The applicable provisions of this Subpart.
ED Decision 2007/013/R
(a) (Reserved)
(b) Engine or drive system cooling fan blade protection.
(1) If an engine or rotor drive system cooling fan is installed, there must be means to protect the rotorcraft and allow a safe landing if a fan blade fails. This must be shown by showing that:
(i) The fan blades are contained in case of failure;
(ii) Each fan is located so that a failure will not jeopardise safety; or
(iii) Each fan blade can withstand an ultimate load of 1.5 times the centrifugal force resulting from operation limited by the following:
(A) For fans driven directly by the engine:
(1) The terminal engine rpm under uncontrolled conditions; or
(2) An overspeed limiting device.
(B) For fans driven by the rotor drive system the maximum rotor drive system rotational speed to be expected in service, including transients.
(2) Unless a fatigue evaluation under CS 27.571 is conducted, it must be shown that cooling fan blades are not operating at resonant conditions within the operating limits of the rotorcraft.
(c) Turbine engine installation. For turbine engine installations, the powerplant systems associated with engine control devices, systems, and instrumentation must be designed to give reasonable assurance that those engine operating limitations that adversely affect turbine rotor structural integrity will not be exceeded in service.
(d) Restart capability. A means to restart any engine in flight must be provided.
(1) Except for the in-flight shutdown of all engines, engine restart capability must be demonstrated throughout a flight envelope for the rotorcraft.
(2) Following the in-flight shutdown of all engines, in-flight engine restart capability must be provided.
[Amdt. No.: 27/1]
ED Decision 2023/001/R
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.
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]
ED Decision 2003/15/RM
(a) Each engine must be installed to prevent the harmful vibration of any part of the engine or rotorcraft.
(b) The addition of the rotor and the rotor drive system to the engine may not subject the principal rotating parts of the engine to excessive vibration stresses. This must be shown by a vibration investigation.
(c) No part of the rotor drive system may be subjected to excessive vibration stresses.