55-22-01 BEECH: Applies to All Model 35 Airplanes, Serial Numbers D-1 Through D- 550, Equipped With Unmodified Oil Tank Check Valves.
Compliance required as soon as possible but not later than January 1, 1956.
To prevent complete loss of the engine oil supply resulting from failure of oil supply line hose connects caused by engine counter rotation, the check valve located at oil tank outlet requires valve modification or removal of the valve internal parts. Modified valves supplied by Beech Aircraft (Beech P/N 35-939082) include 1/16-inch holes drilled in the face of the valve poppet to prevent pressure buildup in the oil supply line in case of engine counter rotation. Modified valves are not available from Beech Aircraft. Unmodified valves should have the internal parts (poppet pivot pin, spring and poppet) removed.
(Beech Service Bulletin Model 35, No. 30, issued July 15, 1955; Service Letter Model 35, No. 44, issued March 28, 1950, and Service Letter Model 35, No. 18, issued July 18, 1947, cover this same subject.)