AD 70-04-04

70-04-04 AIRESEARCH: Amendment 39-944. Applies to Model TPE331-1 and -2 S/N engines: 90005, 90009, 90010, 90011, 90014, 90016, 90017, 90018, 90019, 90022, 90023, 90024, 90027, 90028, 90029, 90030, 91003, 91004, 91005, 91006, 91009, 91011, 91013 thru 91021, 91023, 91024, 91025, 91027, 92001, 92002, 92003, 92004, 92005, 92007, 92010, 92012, 92013, 92014, 92016, thru 92027, 93007, 93008, 93009, 93010; installed in but not limited to Mooney MU-2, Merlin 2B, Volpar Turboliner and Short Skyvan aircraft is effective upon receipt of this telegram. This directive necessary because of a serious engine failure caused by backing off of the high speed pinion retaining nut. To detect and prevent engine failure from this cause, the following is required:

(A) Within 10 hours time in service unless previously accomplished within the last 15 hours time in service, and at intervals not to exceed 25 hours time in service thereafter, remove the engine oil filter and inspect the filter for metal particles. If an abnormal quantity of metal particles is found, accomplish Item (C) before further operation of the engine. At each inspection a replacement filter must be installed and the filter which was removed shall be returned for laboratory examination to AiResearch or to a facility approved by the Chief, Aircraft Engineering Division, Western Region. Any finding of unacceptable metal contamination by AiResearch or other approved facility will be communicated to the owner or operator and the FAA. Upon receipt of such notice the engine shall then not be operated until Item (C) is accomplished. 25 hours oil filter special inspections may be discontinued upon completion of Item (C).

(B) Within 10 hours time in service, install a placard in full view of the pilot to read: 'If abrupt and complete loss of torque indication occurs, shut down the engine and determine the cause.' This placard may be removed when Item (C) is accomplished.

(C) Within 150 hours time in service unless previously accomplished, rework or replace the high speed pinion gear shaft assembly, P/N 869337-2, -3, or -4, in accordance with AiResearch Service Bulletin No. 587, dated 5 February 1970, or later FAA approved revisions.

This amendment is effective upon publication in the Federal Register for all person except those to whom it was made effective immediately by telegram dated February 5, 1970.