54-21-01 AC DIAPHRAGM TYPE FUEL PUMPS: Applies to All Aircraft Powered by Continental, Aircooled or Lycoming Engines Which Are Equipped With AC Diaphragm Type Fuel Pumps.
Compliance required as soon as possible but not later than November 30, 1954.
The occurrence of severe fuel leakage in flight, caused by loosening of AC fuel pump surge chambers, has revealed the existence of AC fuel pumps not adequately safetied to prevent loosening of the sediment bowl and the surge chamber.
The following should be accomplished:
1. Inspect sediment bowl cap screw and surge chamber (if there is one) for adequate safetying.
2. If not safetied, lockwiring or equivalent must be accomplished in accordance with good aircraft practice. One acceptable method of safetying is described by Lycoming Service Bulletin No. 174.