46-38-01 GRUMMAN: (Was Mandatory Note 4 of AD-654-1.) Applies to G-21 and G- 21A Aircraft.
Compliance required prior to November 1, 1946.
Reroute to vacuum system tubing in the engine compartments to prevent raw fuel from lodging in the check valve, thus deteriorating the valve and possible seeping through. The flap system storage tank should be inspected and if fuel is found it should be thoroughly flushed. The check valves in the vacuum system are to be removed and inspected for wear and deterioration. Presence of fuel in the flap system storage tank is sufficient cause for the replacement of the check valves.
(Grumman Service Bulletin No. 19 dated July 18, 1946, covers this same subject.)