Federal Aviation Administration, DOT
Section 29.935

Section 29.952

Shafting joints.

Each universal joint, slip joint, and
other shafting joints whose lubrication
is necessary for operation must have
provision for lubrication.
Section 29.939 Turbine
engine
characteristics.

operating

(a) Turbine engine operating characteristics must be investigated in flight
to determine that no adverse characteristics (such as stall, surge, of flameout) are present, to a hazardous degree,
during normal and emergency operation within the range of operating
limitations of the rotorcraft and of the
engine.
(b) The turbine engine air inlet system may not, as a result of airflow distortion during normal operation, cause
vibration harmful to the engine.
(c) For governor-controlled engines,
it must be shown that there exists no
hazardous torsional instability of the
drive system associated with critical
combinations of power, rotational
speed, and control displacement.
[Amdt. 29-2, 32 FR 6914, May 5, 1967, as
amended by Amdt. 29-12, 41 FR 55473, Dec. 20,
1976]

FUEL SYSTEM

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Section 29.951

General.

(a) Each fuel system must be constructed and arranged to ensure a flow
of fuel at a rate and pressure established for proper engine and auxiliary
power unit functioning under any likely operating conditions, including the
maneuvers for which certification is
requested and during which the engine
or auxiliary power unit is permitted to
be in operation.
(b) Each fuel system must be arranged so that - 
(1) No engine or fuel pump can draw
fuel from more than one tank at a
time; or
(2) There are means to prevent introducing air into the system.
(c) Each fuel system for a turbine engine must be capable of sustained operation throughout its flow and pressure
range with fuel initially saturated with
water at 80 degrees F. and having 0.75cc
of free water per gallon added and
cooled to the most critical condition

for icing likely to be encountered in
operation.
[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as
amended by Amdt. 29-10, 39 FR 35462, Oct. 1,
1974; Amdt. 29-12, 41 FR 55473, Dec. 20, 1976]

Section 29.952 Fuel system crash resistance.
Unless other means acceptable to the
Administrator are employed to minimize the hazard of fuel fires to occupants following an otherwise survivable impact (crash landing), the fuel
systems must incorporate the design
features of this section. These systems
must be shown to be capable of sustaining the static and dynamic deceleration loads of this section, considered as ultimate loads acting alone,
measured at the system component-s
center of gravity without structural
damage to the system components, fuel
tanks, or their attachments that would
leak fuel to an ignition source.
(a) Drop test requirements. Each tank,
or the most critical tank, must be
drop-tested as follows:
(1) The drop height must be at least
50 feet.
(2) The drop impact surface must be
nondeforming.
(3) The tanks must be filled with
water to 80 percent of the normal, full
capacity.
(4) The tank must be enclosed in a
surrounding structure representative
of the installation unless it can be established that the surrounding structure is free of projections or other design features likely to contribute to
upture of the tank.
(5) The tank must drop freely and impact in a horizontal position Section10Section.
(6) After the drop test, there must be
no leakage.
(b) Fuel tank load factors. Except for
fuel tanks located so that tank rupture
with fuel release to either significant
ignition sources, such as engines, heaters, and auxiliary power units, or occupants is extremely remote, each fuel
tank must be designed and installed to
retain its contents under the following
ultimate inertial load factors, acting
alone.
(1) For fuel tanks in the cabin:
(i) Upward - 4g.
(ii) Forward - 16g.
(iii) Sideward - 8g.
(iv) Downward - 20g.

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