Federal Aviation Administration, DOT

Section 27.952

drive system associated with critical
combinations of power, rotational
speed, and control displacement.
[Amdt. 27-1, 32 FR 6914, May 5, 1967, as
amended by Amdt. 27-11, 41 FR 55469, Dec. 20,
1976]

FUEL SYSTEM
Section 27.951 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 functioning
under any likely operating condition,
including the maneuvers for which certification is requested.
(b) Each fuel system must be arranged so that - 
(1) No 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 SectionF. 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.

spaschal on DSK3GDR082PROD with CFR

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as
amended by Amdt. 27-9, 39 FR 35461, Oct. 1,
1974]

Section 27.952 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 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 tank 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
rupture 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.
(2) For fuel tanks located above or
behind the crew or passenger compartment that, if loosened, could injure an
occupant in an emergency landing:
(i) Upward - 1.5g.
(ii) Forward - 8g.
(iii) Sideward - 2g.
(iv) Downward - 4g.
(3) For fuel tanks in other areas:
(i) Upward - 1.5g.
(ii) Forward - 4g.
(iii) Sideward - 2g.
(iv) Downward - 4g.
(c) Fuel line self-sealing breakaway
couplings. Self-sealing breakaway couplings must be installed unless hazardous relative motion of fuel system
components to each other or to local
rotorcraft structure is demonstrated to
be extremely improbable or unless
other means are provided. The couplings or equivalent devices must be
installed at all fuel tank-to-fuel line
connections, tank-to-tank interconnects, and at other points in the fuel
system where local structural deformation could lead to the release of fuel.
(1) The design and construction of
self-sealing breakaway couplings must

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