(a) Engine type certification. Each engine must have an approved
type certificate. Reciprocating engines for use in helicopters must be
qualified in accordance with §33.49(d) of this chapter or be otherwise
approved for the intended usage.
(b) Category A; engine isolation. For each category A
rotorcraft, the powerplants must be arranged and isolated from each other
to allow operation, in at least one configuration, so that the failure or
malfunction of any engine, or the failure of any system that can affect
any engine, will not --
(1) Prevent the continued safe operation of the remaining engines; or
(2) Require immediate action, other than normal pilot action with
primary flight controls, by any crewmember to maintain safe operation.
(c) Category A; control of engine rotation. For each Category A
rotorcraft, there must be a means for stopping the rotation of any engine
individually in flight, except that, for turbine engine installations, the
means for stopping the engine need be provided only where necessary for
safety. In addition --
(1) Each component of the engine stopping system that is located on the
engine side of the firewall, and that might be exposed to fire, must be at
least fire resistant; or
(2) Duplicate means must be available for stopping the engine and the
controls must be where all are not likely to be damaged at the same time
in case of fire.
(d) Turbine engine installation. For turbine engine
(1) Design precautions must be taken to minimize the hazards to the
rotorcraft in the event of an engine rotor failure; and
(2) 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 engine rotor
structural integrity will not be exceeded in service.
(e) Restart capability. (1) A means to restart any engine in
flight must be provided.
(2) Except for the in-flight shutdown of all engines, engine restart
capability must be demonstrated throughout a flight envelope for the
(3) Following the in-flight shutdown of all engines, in-flight engine
restart capability must be provided. (Secs. 313(a), 601, and 603,
72 Stat. 752, 775, 49 U.S.C. 1354(a), 1421, and 1423; sec. 6(c), 49 U.S.C.