# AD 71-05-02: Crankcase Main Bearings - Type: Airworthiness directive - Status: Current - Products: Lycoming Engines IO-360-A1A, IO-360-A1B, IO-360-A1B6, IO-360-A1C, IO-360-A1D6, IO-360-A2A, IO-360-A2B, IO-360-A2C, IO-360-C1A, IO-360-C1B, IO-360-C1C and IO-360-C1D6 - Effective: February 13, 1973 - Superseded by: Nothing supersedes this AD - Product type: Engine - Amendment: 39-1589 - Registered aircraft: 7,047 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/629B43B6E240426D86256E01005ACFF6.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/71-05-02 ## The airworthiness directive 71-05-02 AVCO LYCOMING: Amdt. 39-1158 as amended by Amendment 39-1402, 39-1537 and 39-1550 is further amended by Amendment 39-1589. Applies to all IO-360-A and -C series engines except S/N 7100-51A and subsequent and except all engines overhauled (also known as remanufactured) by Lycoming after 26 January 1970 except S/N 354-51, 1049-51A, 3003-51A, 3281-51A, 6526-51A. To prevent shifting and possible failures of the crankcase main bearings, perform the following: (a) Engines that have accumulated less than 500 hours in service since new or overhaul must have the lubrication system inspected for metal contaminants within the next 10 hours in service after the effective date of this AD and every 25 hours in service until 525 hours in service are accumulated, at which time compliance with (d) or (f) is required. Inspection of the lubrication system consists of visual examination for minute particles of metal suspended in the oil, examination of the engine oil suction screen for presence of metal particles and the inspection of the external full flow oil filter for metal particles by cutting it open so that the pleated element can be unfolded and examined. (b) Engines that have accumulated 500 hours or more in service since new or overhaul must have the lubrication system inspected for metal contaminants within the next 10 hours in service after the effective date of this AD. Further, compliance with (d) or (f) is required within 25 hours in service after the effective date of this AD. (c) Compliance with (d) or (f) is required if metal contaminants are detected during the above inspections. (d) Remove number two position cylinder and examine visually the position of the center main bearing for shifting in accordance with the inspection procedure of Avco Lycoming Service Bulletin No. 327B or equivalent inspection approved by Chief, Engineering and Manufacturing Branch FAA, Eastern Region. Should shifting be detected, comply with paragraph (f). If thebearing has not shifted and no metal contaminants are detected after compliance with paragraph (a) or (b) the engine can be returned to service and the lubrication system must be inspected for contaminants every 50 hours in service thereafter. (e) Unless already accomplished, compliance with paragraph (f) is required within 50 hours in service after the effective date of this AD on engines that have accumulated 1150 hours or more in service since new or last overhaul. (f) Modify the crankcase as described in Lycoming Service Instructions No. 1123A or repair the crankcase as described in Lycoming Service Instructions No. 1112C, whichever is applicable, and install straight crankcase bearing dowels per Lycoming Service Bulletin No. 326 or equivalent repair or alteration approved by Chief, Engineering and Manufacturing Branch, FAA, Eastern Region. Compliance with the provisions of this paragraph eliminates the inspection requirements of this AD. (NOTE: The inspection of the lubrication system required by this AD constitutes preventive maintenance.) Amendment 39-1158 was effective February 23, 1971. Amendment 39-1402 was effective March 14, 1972. Amendment 39-1537 was effective October 17, 1972. Amendment 39-1550 was effective upon publication in the Federal Register. This amendment 39-1589 is effective February 13, 1973. ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS 1E10](https://openairdocs.org/tcds/1E10): Lycoming Engines; names 12 of 89 models: IO-360-C1D6, IO-360-A2A, IO-360-A1C, IO-360-A2B, IO-360-C1B, IO-360-A1A, IO-360-A2C, IO-360-A1B… ## Registered aircraft it may apply to (OpenAirDocs) Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment. - Aircraft: 7,047 (0 by airframe model, 7,047 by engine model) - Makers: Piper 2,098, Mooney 1,888, Cessna 720, Beech 446, Aviat 188, Diamond Aircraft Ind 175, Rockwell International 129, Aero Commander 74, Lake 57, Aerotek 46 Models with the most aircraft: - [Lycoming I0360 series](https://openairdocs.org/engine/lycoming-i0360-series): 6,174 aircraft (engine model) - [Lycoming IO-360 series](https://openairdocs.org/engine/lycoming-io-360-series): 217 aircraft (engine model) - [Lycoming IO-360-A1A](https://openairdocs.org/engine/lycoming-io-360-a1a): 196 aircraft (engine model) - [Lycoming IO-360-A1D6](https://openairdocs.org/engine/lycoming-io-360-a1d6): 192 aircraft (engine model) - [Lycoming IO-360-A1B6](https://openairdocs.org/engine/lycoming-io-360-a1b6): 141 aircraft (engine model) - [Lycoming IO-360-A1B](https://openairdocs.org/engine/lycoming-io-360-a1b): 52 aircraft (engine model) - [Lycoming IO-360-C1C](https://openairdocs.org/engine/lycoming-io-360-c1c): 45 aircraft (engine model) - [Lycoming IO-360-C1D6](https://openairdocs.org/engine/lycoming-io-360-c1d6): 14 aircraft (engine model) - [Lycoming I0-360 series](https://openairdocs.org/engine/lycoming-i0-360-series): 7 aircraft (engine model) - [Lycoming IO-360-C1A](https://openairdocs.org/engine/lycoming-io-360-c1a): 7 aircraft (engine model) - [Lycoming IO-360-A2B](https://openairdocs.org/engine/lycoming-io-360-a2b): 2 aircraft (engine model) All 11 models: https://openairdocs.org/ad/71-05-02/models.md Every aircraft: https://openairdocs.org/ad/71-05-02/aircraft.md Its text cites no advisory circulars or STCs. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.