AD 74-22-01

74-22-01 MCDONNELL DOUGLAS: Amendment 39-1995, as amended by amendment 39-3487. Applies to all Model DC-9 -10, -20, -30, -40 and military C-9A and C-9B Series airplanes equipped with welded aft engine isolator mount(s), P/N K2219-6SA3, certificated in all categories.

To detect cracks in the welded aft engine mounts, accomplish the following:

For airplanes equipped with welded aft engine isolator mount(s) with more than 4,000 hours time-in-service on the effective date of this AD, within the next 300 hours time-in-service, unless previously accomplished within the last 450 hours time-in-service, and thereafter at intervals not to exceed 850 hours time-in-service, inspect the aft engine mount per McDonnell Douglas All Operators' Letter AOL 9-786, dated December 13, 1973, AOL 9-786A dated March 27, 1974, AOL 9-786B dated April 8, 1974, or an equivalent approved by the Chief, Aircraft Engineering Division, FAA Western Region. If any cracks are detected replace the part before further flight with a forged part, P/N's K2219-6SA5 and K2219-7SA3, or an uncracked welded part K2219-6SA3. Upon installation of a forged part the requirements of this A.D. are terminated.

NOTE: (A) For the purposes of this A.D. if the time-in-service hours of the aft engine isolator mount cannot be established the part will be considered to have the same number of time-in-service hours as the airplane on which it is installed.

(B) The airplane may be flown in accordance with FAR's 21.197 21.199 to a base where the inspection can be performed.

Amendment 39-1995 became effective November 25, 1974.

This amendment 39-3487 becomes effective June 12, 1979.