AD 55-15-04

55-15-04 DOUGLAS: Applies to all DC-6 Series Airplanes Below fuselage No. 487 Equipped With Hamilton Standard Propellers.

Compliance required by first scheduled engine change after November 1, 1955, but not later than November 1, 1956.

To increase the integrity of the propeller feathering system in the event of a powerplant fire, all existing propeller feathering lines located forward of the firewall must be replaced with lines and flexible hose assemblies which will meet current fireproof and fire resistant requirements.

(a) Replace the existing flexible hose portion of the feathering line between the union on the forward pipe assembly and the elbow on the inner ring with a new hose assembly Aeroquip P/N 304004-10-17 1/2. Douglas General Service Letter DC-6 No. 206 dated August 26, 1954, covers this subject. Resistoflex SSFR-3800-10 hose assembly and Aeroquip 309009-10S hose assembly are also considered acceptable for this application.

(b) The existing flexible hose assembly connecting to the governor is not affected by this directive.

(c) Remove the existing short 304 sleeves or flexible metal sleeve from the feathering pump supply line, Aeroquip P/N 304002-16D-12 3/8, and install a fireproof cover, Douglas P/N 3500614-1. Douglas General Service Letter DC-6 No. 206 dated August 26, 1954, covers this subject. Aeroquip 601000 hose assembly equipped with Aeroquip 304 full length protective sleeve or Aeroquip 680-16S hose assembly equipped with Aeroquip 304 short sleeves covering the end fittings are also considered acceptable for this application.