780 

14 CFR Ch. I (1–1–14 Edition) 

§ 29.952 

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] 

§ 29.952

Fuel system crash resistance. 

Unless other means acceptable to the 

Administrator are employed to mini-
mize the hazard of fuel fires to occu-
pants following an otherwise surviv-
able impact (crash landing), the fuel 
systems must incorporate the design 
features of this section. These systems 
must be shown to be capable of sus-
taining the static and dynamic decel-
eration loads of this section, consid-
ered 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 es-
tablished that the surrounding struc-
ture is free of projections or other de-
sign features likely to contribute to 
upture of the tank. 

(5) The tank must drop freely and im-

pact in a horizontal position 

±

10

°

. 

(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, heat-
ers, and auxiliary power units, or occu-
pants 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 compart-
ment 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 cou-
plings must be installed unless haz-
ardous 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 cou-
plings or equivalent devices must be 
installed at all fuel tank-to-fuel line 
connections, tank-to-tank intercon-
nects, and at other points in the fuel 
system where local structural deforma-
tion could lead to the release of fuel. 

(1) The design and construction of 

self-sealing breakaway couplings must 
incorporate the following design fea-
tures: 

(i) The load necessary to separate a 

breakaway coupling must be between 
25 to 50 percent of the minimum ulti-
mate failure load (ultimate strength) 
of the weakest component in the fluid- 
carrying line. The separation load 
must in no case be less than 300 pounds, 
regardless of the size of the fluid line. 

(ii) A breakaway coupling must sepa-

rate whenever its ultimate load (as de-
fined in paragraph (c)(1)(i) of this sec-
tion) is applied in the failure modes 
most likely to occur. 

(iii) All breakaway couplings must 

incorporate design provisions to vis-
ually ascertain that the coupling is 
locked together (leak-free) and is open 
during normal installation and service. 

(iv) All breakaway couplings must in-

corporate design provisions to prevent 
uncoupling or unintended closing due 
to operational shocks, vibrations, or 
accelerations. 

(v) No breakaway coupling design 

may allow the release of fuel once the 

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