774
14 CFR Ch. I (1–1–14 Edition)
§ 29.907
(1) Design precautions must be taken
to minimize the hazards to the rotor-
craft in the event of an engine rotor
failure; and
(2) The powerplant systems associ-
ated with engine control devices, sys-
tems, and instrumentation must be de-
signed to give reasonable assurance
that those engine operating limitations
that adversely affect engine rotor
structural integrity will not be exceed-
ed 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 rotorcraft.
(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. 1655(c))
[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as
amended by Amdt. 29–12, 41 FR 55472, Dec. 20,
1976; Amdt. 29–26, 53 FR 34215, Sept. 2, 1988;
Amdt. 29–31, 55 FR 38967, Sept. 21, 1990; 55 FR
41309, Oct. 10, 1990; Amdt. 29–36, 60 FR 55776,
Nov. 2, 1995]
§ 29.907
Engine vibration.
(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 vi-
bration investigation.
§ 29.908
Cooling fans.
For cooling fans that are a part of a
powerplant installation the following
apply:
(a)
Category A. For cooling fans in-
stalled in Category A rotorcraft, it
must be shown that a fan blade failure
will not prevent continued safe flight
either because of damage caused by the
failed blade or loss of cooling air.
(b)
Category B. For cooling fans in-
stalled in category B rotorcraft, there
must be means to protect the rotor-
craft and allow a safe landing if a fan
blade fails. It must be shown that—
(1) The fan blade would be contained
in the case of a failure;
(2) Each fan is located so that a fan
blade failure will not jeopardize safety;
or
(3) Each fan blade can withstand an
ultimate load of 1.5 times the cen-
trifugal force expected in service, lim-
ited by either—
(i) The highest rotational speeds
achievable under uncontrolled condi-
tions; or
(ii) An overspeed limiting device.
(c)
Fatigue evaluation. Unless a fa-
tigue evaluation under § 29.571 is con-
ducted, it must be shown that cooling
fan blades are not operating at reso-
nant conditions within the operating
limits of the rotorcraft.
(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. 1655 (c))
[Amdt. 29–13, 42 FR 15046, Mar. 17, 1977, as
amended by Amdt. 29–26, 53 FR 34215, Sept. 2,
1988]
R
OTOR
D
RIVE
S
YSTEM
§ 29.917
Design.
(a)
General. The rotor drive system
includes any part necessary to trans-
mit power from the engines to the
rotor hubs. This includes gear boxes,
shafting, universal joints, couplings,
rotor brake assemblies, clutches, sup-
porting bearings for shafting, any at-
tendant accessory pads or drives, and
any cooling fans that are a part of, at-
tached to, or mounted on the rotor
drive system.
(b)
Design assessment. A design assess-
ment must be performed to ensure that
the rotor drive system functions safely
over the full range of conditions for
which certification is sought. The de-
sign assessment must include a de-
tailed failure analysis to identify all
failures that will prevent continued
safe flight or safe landing and must
identify the means to minimize the
likelihood of their occurrence.
(c)
Arrangement. Rotor drive systems
must be arranged as follows:
(1) Each rotor drive system of multi-
engine rotorcraft must be arranged so
that each rotor necessary for operation
and control will continue to be driven
by the remaining engines if any engine
fails.
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