CS 27.952 (c) as of Initial Issue onwards requires self-sealing breakaway couplings to seal off lines and prevent fuel spillage if fuel system components are displaced in a crash.
Further, and more specifically, for fuel lines with breakaway couplings, subparagraph CS 27.952(c)(1)(i) states “The load necessary to separate a breakaway coupling must be between 25 to 50 percent of the minimum ultimate 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.” FAA Advisory Circular 27-1B §27.952 d(5) states that the minimum 300-pound load is necessary to prevent ground maintenance failures.
EASA received an application involving a tank and fuel system design where the separation loads of the couplings for specific load cases do not directly comply with the specific minimum value of 1334 N (300 lb)).
Considering all the above, the following Equivalent Safety Finding is proposed.
Official comments to the proposed consultation paper are to be filed through the EASA Comment-Response Tool (CRT)
Details
Identification of issue
CS 27.952 (c) as of Initial Issue onwards requires self-sealing breakaway couplings to seal off lines and prevent fuel spillage if fuel system components are displaced in a crash.
Further, and more specifically, for fuel lines with breakaway couplings, subparagraph CS 27.952(c)(1)(i) states “The load necessary to separate a breakaway coupling must be between 25 to 50 percent of the minimum ultimate 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.” FAA Advisory Circular 27-1B §27.952 d(5) states that the minimum 300-pound load is necessary to prevent ground maintenance failures.
EASA received a helicopter manufacturer’s application involving a tank and fuel system design where the seperation loads of the couplings for specific load cases do not directly comply with the specific minimum value of 1334 N (300 lb)).
Considering all the above, the following Equivalent Safety Finding is proposed