§29.965 Fuel tank tests

(a) Each fu el tan k m ust b e ab le to withstand the ap plicable p ressure tests in this paragraph without fai lure or l eakage. If pract icable, test pressures m ay be appl ied i n a m anner simulating the pressure distribution in service. (b) Each conventional m etal tank, each non-metallic tank with walls that are not supported by the rotorcraft structure, and each integral tank must be subjected to a pressure of 24 kPa (3.5 psi) unless t he pressure devel oped duri ng m aximum limit acceleration or em ergency deceleration with a full tank exceeds this value, in which case a hydrostatic head, or equi valent test, must be applied to duplicate the acceleration loads as far as possible. However, the pressure need not exceed 24 kPa (3.5 psi) on surfaces not exposed to the acceleration loading. (c) Each non-m etallic tank with walls supported by t he rot orcraft st ructure m ust be subjected to the following tests: (1) A pressure test of at least 14 kPa (2.0 psi). This test may be conducted on the tank alone in conjunction with th e test sp ecified in subparagraph (c)(2). (2) A pressure test, with the tank mounted in the rotorcraft structure, equal to the load developed by the reaction of t he contents, with th e tan k fu ll, d uring m aximum limit acceleration or em ergency deceleration. However, the pressure need not exceed 14 kPa (2.0 psi) on surfaces not exposed to the acceleration loading. (d) Each t ank wi th l arge unsupported or unstiffened flat areas, or with other features whose failure or deform ation coul d cause leakage, must be subjected to the following test or its equivalent: (1) Each co mplete tan k assembly and its supports m ust be vi bration t ested whi le mounted to simulate the actual installation. (2) The tank assembly must be vi brated for 25 hours whi le t wo-thirds ful l of any suitable fl uid. The am plitude of vi bration m ay not be l ess t han 0.8 m m (one t hirty-second of an inch), unless otherwise substantiated. (3) The test frequency of vibration must be as follows: (i) If no frequency of vibration resulting from any rpm within the normal operating range of engine or rot or system speeds is critical, the test frequency of vibration, in number of cycles per minute, must, unless a frequency based on a more rational anal ysis i s used, be t he number obtained by averagi ng t he maximum and minimum power-on engi ne speeds (rpm ) for reciprocating engi ne powered rotorcraft or 2000 cpm for turbine engine powered rotorcraft. (ii) If onl y one frequency of vibration resul ting from any rpm within the norm al operat ing range of engi ne or rotor system speeds is critical, that frequency of vi bration m ust be the test frequency. (iii) If more th an o ne freq uency o f vibration resul ting from any rpm within the norm al operat ing range of engi ne or rotor system speeds is critical, the m ost critical of these frequencies m ust be the test frequency. (4) Under sub-paragraph (d)(3)(i i) and (iii), t he t ime o f t est m ust b e a djusted to accomplish the sam e num ber of vibration cycles as would be accom plished in 25 hours at the frequency speci fied i n sub-paragraph (d)(3)(i). (5) During th e test th e tan k assem bly must be rocked at the rate of 16 t o 20 complete cycles per m inute t hrough an angl e of 15° on both si des of t he hori zontal (30° total), about the m ost cri tical axi s, for 25 hours. If motion about more than one axis is likely to be critical, the tank must be rocked about each critical axis for 12½ hours.