AD 50-25-01

50-25-01 STINSON: Applies to All Model 108 Series Aircraft. Compliance required not later than September 1, 1950. Reports have been received of fuel seepage into the space between the inner cabin trim and the outer fabric covering of the fuselage. This results in soaking of insulating material in the cabin wall. The source of the fuel can be spillage during filling of tanks, thermal expansion of fuel in full tanks, or tank leakage. This fuel runs to the under surface of the wing, adhering to the lower curved surface of the trailing edge of the wing at the flap well, thence inboard to the fuselage and across the rear window. Since the window seal is often not perfectly tight the fuel may then enter the cabin wall. To preclude the fire hazard of fuel soaked insulation within the cabin wall due to these causes, a drip strip similar to that shown in Figure 1 should be installed on the underside of each wing. This drip strip will prevent fuel from flowing from the wing to the fuselage. (Piper Service Bulletin No. 115, dated March 31, 1950, covers this same subject.)