AD 54-22-01

54-22-01 LOCKHEED: Applies to Models 49, 649, 749, and 1049 Airplanes as Noted in Referenced Service Bulletins.

Compliance required by April 1, 1955.

A recent engine fire resulted in a premature failure of a flexible hose in the feathering line and in penetration of fire from zone 1 into zone 2.

1. To increase the fire resistance integrity of the propeller feathering line between the pump and the governor, replace the existing flexible hose assemblies meeting current fire resistance requirements. The following Lockheed Service Bulletins cover this subject: No. 49/SB-786 for Model 049 through 749 airplanes and No. 1049/SB-2195 for Model 1049 airplanes. The following hose assemblies may also be considered acceptable for this application:

(a) Aeroquip 680-10S hose assemblies with Aeroquip 304 protective sleeves over end fittings.

(b) Resistoflex - SSFR-3800-10 hose assemblies.

2. To increase the fireproof integrity of the zone 1 fire seal diaphragm against burn-through into zone 2 in the event of a power section fire install steel plates over the lower engine cowling longerons adjacent to the diaphragm. The following Lockheed Service Bulletins cover this subject: No. 49/SB-760 for Model 649/749 airplanes and No. 1049/SB-2115 for Model 1049 airplanes.