Mr. George S. Moore (2)
1. Fuel lines through the fuselage should be rerouted that they pass through the floor beams near the centerline of the aircraft.
2. The fuel lines and their shrouds should be made of stainless steel and should have a wall thickness of sufficient dimension to withstand rather severe impacts. We suggest that the wall thicknesses be not less than 0.040 inch.
3. The generator leads should be routed so that there is maximum separation between these leads and the fuel lines. Each lead should be in a separate plastic conduit with suitable strength and flexibility to withstand bending and reasonably high tensile load.
In regard to recommendation No. 1 above, it should be pointed out that his aircraft struck the ground with a recorded impact of 8.9 g's after the landing gear failure but despite this heavy impact the aft fuselage belly structure did not collapse; In other words, had the fuel lines been running through the center area of the floor beam, they would have been adequately protected. In support of recommendation No. 2, it was noted during the investigation that although the aluminum tubing and shroud of fuel line No. l did not melt, those of lines No. 2 and No. 3 did melt in areas other than the break points. Thus, fire from one broken line could melt through the present aluminum tubing and shroud of another line and thereby increase the intensity of an existing fire.
It is our understanding that both FAA and Boeing personnel who participated in the investigation of the Salt Lake City accident have made similar recommendations through their own organizational channels.
We also recommend that all other similarly configured aircraft (e.g., DC-9, Lear Jet, Caravelle, BAC 111, Jet Commander) be the subjects of a study to determine whether or not analogous dangers exist in their fuel and electrical system geometries.
Should your staff desire further information or wish to discuss the problem further, we can make appropriate members of the investigating team available at any time.
Sincerely yours,
/s/ B. R. Allen
B. R. Allen
Director, Bureau of Safety
