AD 79-12-04

79-12-04 AIRESEARCH MANUFACTURING COMPANY OF ARIZONA: Amendment 39-3486. Applies to all AiResearch Model TPE 331-10-501G engines incorporating the forged third stage turbine wheel, Part Number 3101516-1, installed in the Swearingen Merlin IIIB airplane. NOTE: The engine and airplane manufacturer's records indicate that the subject forged third stage turbine wheels, Part Number 3101516-1, are contained in the following serial numbered TPE 331-10-501G turboprop engines and are installed on the following Swearingen Merlin IIIB airplanes:

Engine Airplane Serial Number Serial Number Airplane Registration

P35003 T292 LVBHP P35004 T292 (Argentina) P35008 T294 N800TA P35010 T294 (Teterbury Aviation, NJ) P35009 T295 N4442F P35012 T295 (Fairchild) P35011 T296 VHSWK P35013 T296 (Stillwell; in Australia) P35017 T298 N5495M P35019 T298 (Stillwell; in Australia) P35014 T297 N5465M P35015 T297 (Planes, Inc.; Atlanta, GA)P35016 T299 N81CH P35020 T299 (Duncan Aviation, NB) P35022 T300 N29TA P35023 T300 (Teterbury Aviation, NJ) P35021 T301 N5652M P35024 T301 (Western Airmotive, Hillsboro, OR) P35025 T302 N5497M P35026 T302 (Houston, TX) P35007 T293 DIBB (Cologne, Germany) P35018 T276 N5111B (Philadelphia)

Compliance required as indicated. To reduce the possible hazard from the total loss of power of one or more engines during a single flight resulting from the failure of the forged third stage turbine wheel blade, accomplish the following. (a) Within the next 10 operating hours time in service after May 10, 1979, on at least one of the affected TPE 331-10-501G engines on each affected airplane, unless already accomplished, remove the forged third stage turbine wheel, Part Number 3101516-1, and replace it with a cast third stage turbine wheel, Part Number 3102655-1, in accordance with existing maintenance instructions. NOTE: Suitable instructions may be found in TPE 331-10 Engine Maintenance Manual, AiResearch Part Number 72-00-23. (b) Within the next 50 operating hours time in service after May 10, 1979, on all TPE 331-10-501G engines installed on the Merlin IIIB airplane, unless already accomplished, remove the forged third stage turbine wheel, Part Number 3101516-1, and replace it with a cast third stage turbine wheel, Part Number 3102655-1, in accordance with instructions referenced in Paragraph (a) of this airworthiness directive. (c) Alternative actions which provide an equivalent level of safety may be used when approved by the Chief, Aircraft Engineering Division, FAA Western Region. (d) 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 the actions required by this AD. (e) Upon request of operator, an FAA maintenance inspector, subject to prior approval of the Chief, Aircraft Engineering Division, FAA Western Region may adjust the initial and repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for that operator. This amendment becomes effective upon publication in the Federal Register as to all person except those persons to whom it was made immediately effective by telegram dated May 10, 1979, which contains this amendment.