AD 79-25-01

79-25-01 MCDONNELL DOUGLAS: Amendment 39-3627 as amended by Amendment 39-3702. Applies to McDonnell Douglas Model DC-10-10, -10F, -30, -30F, and -40 series airplanes certificated in all categories.

Compliance required as indicated, unless already accomplished.

To preclude contamination from preventing proper operation of the AiResearch Positive Pressure Relief Valves, accomplish the following:

(1) Within the next 300 hours time in service after the effective date of this AD,

(a) Modify and reidentify the AiResearch P/N 103506-2 cabin pressure relief valves by the addition of an improved filter in accordance with Douglas Service Bulletin 21-87 dated December 3, 1975 (AiResearch Service Bulletin 103506-21-2271, Revision #1, dated May 15, 1979) or AiResearch Service Bulletin 103506-21-2307, dated June 15, 1978 immediately following cleaning of the valve metering system in accordance with Douglas Service Bulletin A21-103, Revision 1, dated August 7, 1978; or(b) Unless already accomplished within the preceding 3,000 flight-hours prior to the effective date of this AD,

(i) Disassemble, clean and reassemble the AiResearch P/N 103506-2 cabin pressure relief valves metering systems and adjust/test valves in accordance with Douglas Service Bulletin A21-103, Revision 1, dated August 7, 1978; or

(ii) Replace the AiResearch P/N 103506-2 cabin positive pressure relief valves with P/N 103506-2 valves having clean metering systems and test valves in accordance with Douglas Service Bulletin A21-103, Revision 1, dated August 7, 1978.

(2) If paragraph (1)(a) above is accomplished, at intervals not to exceed 8,000 hours' time in service thereafter, change the relief valve filter elements and functionally check per the maintenance manual. For airplanes with relief valve filters installed per paragraph (1)(a) of this AD, with total filter time in service of 8,000 or more hours on January 7, 1980; within the next 1,000 hours' time in service after January 7, 1980, and thereafter, at intervals not to exceed 8,000 hours' time in service change the relief valve filter elements and functionally check the valve per the maintenance manual.

(3) Unless paragraph (1)(a) is accomplished, paragraph (1)(b)(i) or (1)(b)(ii) must be accomplished within 3,000 hour intervals since previous accomplishment, and the original delivery design positive pressure relief valve filter elements must be changed per the Maintenance Manual within 1,500 hour intervals since previous accomplishment.

(4) If AiResearch P/N 103624-1 or -2 cabin positive pressure relief valves are installed, prior to the accumulation of 8,000 hours' time in service on the relief valve filter elements, and at intervals not to exceed 8,000 hours' time in service thereafter, change the relief valve filter elements and functionally check valve per the maintenance manual.

Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base for the accomplishment of inspections required by this AD.

Alternative inspections, modifications or other actions which provide an equivalent level of safety may be used when approved by the Chief, Aircraft Engineering Division, FAA Western Region.

Amendment 39-3627 became effective January 7, 1980.

This Amendment 39-3702 becomes effective March 3, 1980, and was effective earlier to all recipients of telegraphic AD T80WE-1 dated January 4, 1980.