71-16-01 de HAVILLAND AIRCRAFT of CANADA LTD: Amdt. 39-1250. Applies to de Havilland Type DHC-6 Aircraft, Serial Numbers 1 through 299, inclusive.
Compliance required, unless already accomplished, within 30 days after the effective date of this AD for aircraft which have been in service for 12 months or more from the date of first flight. For aircraft which have been in service less than 12 months, compliance required within 30 days after the accumulation of 12 months' service.
To preclude the possibility of engine flameout due to fuel starvation in the event of separation of the flapper valve seal in fuel cells No. 4 and No. 5, replace No. 4 and No. 5 flapper valve assemblies, P/N C6PF1026-3, with new like parts and repeat replacement thereafter at 12- month intervals until such time as DHC modifications 6/1406 is incorporated in accordance with instructions contained in DHC Service Bulletin No. 6/269, dated February 19, 1971, or an equivalent modification approved bythe Chief, Engineering & Manufacturing Branch, Federal Aviation Administration, Eastern Region.
This amendment is effective August 3, 1971.