# AD 74-06-01: AiResearch Turbochargers - Type: Airworthiness directive - Status: Historical - Products: PA-23-235, PA-23-250 (Navy UO-1) and PA-E23-250 with STC SA852WE or 2 others - Effective: October 2, 1974 - Superseded by: [AD 2005-01-10](https://openairdocs.org/ad/2005-01-10) - Product type: Aircraft, Small airplane - Amendment: 39-1977 - Registered aircraft: 924 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/F477099E8F378A5D86256E1200498D9A.0001 - DRS record last changed: August 7, 2025 - Page: https://openairdocs.org/ad/74-06-01 ## The airworthiness directive 74-06-01 PIPER: Amendment 39-1799 is amended by Amendment 39-1977. Applies to Piper Models PA-23-235, PA-23-250 and PA-E23-250 airplanes certificated in all categories with AiResearch turbosuperchargers installed in accordance with STC SA852WE, SA909WE or SA978WE,. or installed in accordance with Piper Aircraft Corporation Drawing 32016. Compliance required as indicated, unless previously accomplished. To minimize fire hazards related to engine compartment fires, accomplish the following in accordance with AiResearch Aviation Company Service Bulletin No. 14.1.10, dated February 6, 1974 or later FAA-approved revision, for serial numbers 27-2505 and subsequent (Aztec C, Aztec D, Aztec E), and, in accordance with AiResearch Service Bulletin No. 14.1.11, dated February 6, 1974 or later FAA-approved revision for serial numbers 27-1 through 27-2504 (Aztec, Aztec B, Apache 235): (a) Within the next 25 hours' time in service after the effective date of this airworthinessdirective, add drainage provisions in the airscoops, AiResearch Part No. 286-P23-066-5, of airplanes serial numbers 27-2505 and subsequent. (b) Within the next 600 hours' time in service or 365 days after March 18, 1974, whichever occurs first: (1) For airplanes serial numbers 27-1 through 27-2504: (i) Replace the existing turbosupercharger oil tanks with AiResearch Part No. 286-P23-028-81F oil tanks. (ii) Install AiResearch Part No. 286-P23-028-231 fire shrouds and seal all openings in the fire shrouds. (iii) Add drainage provisions in the oil tank fairings, AiResearch Part No. 286-P23-057. (2) For airplanes serial number 27-2505 and subsequent: (i) Replace the existing turbosupercharger oil tanks with AiResearch Part No. 286-P23-028-111F oil tanks. (ii) Seal all openings in the fire shrouds, AiResearch Part No. 286- P23-064-153. (c) Equivalent modification may be approved by the Chief, Aircraft Engineering Division, FAA WesternRegion. (d) Aircraft may be flown to a base where the maintenance required by this airworthiness directive may be performed per FARs 21.197 and 21.199. NOTE: For the requirements regarding the listing of compliance of and method of compliance with this airworthiness directive in the permanent maintenance record of the airplane, see FAR 91.173. NOTE: The extended compliance time authorized by this amendment to AD 74-06-01, as set forth in (b) above, shall be retroactive to September 14, 1974, to permit aircraft operations beyond 180 days after March 18, 1974. Amendment 39-1799 became effective March 18, 1974. This Amendment 39-1977 becomes effective October 2, 1974. ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS 1A10](https://openairdocs.org/tcds/1A10): Piper Aircraft Inc.; names 3 of 6 models: PA-23-235, PA-E23-250, PA-23-250 (Navy UO-1) ## 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: 924 (924 by airframe model, 0 by engine model) - Makers: Piper 924 Models with the most aircraft: - [Piper PA-23-250](https://openairdocs.org/model/piper-pa-23-250): 894 aircraft (airframe model) - [Piper PA-23-235](https://openairdocs.org/model/piper-pa-23-235): 25 aircraft (airframe model) - [Piper PA-23-250 (6PCLM)](https://openairdocs.org/model/piper-pa-23-250-6pclm): 5 aircraft (airframe model) All 3 models: https://openairdocs.org/ad/74-06-01/models.md Every aircraft: https://openairdocs.org/ad/74-06-01/aircraft.md ## Related documents - [AD 2005-01-10](https://openairdocs.org/ad/2005-01-10): Turbocharger Oil Reservoir ยท Piper PA-23-235, PA-23-250, PA-23-250 (Navy UO-1) and 1 more. Effective Feb 22, 2005. Supersedes this AD - [STC SA852WE](https://openairdocs.org/stc/SA852WE): Turbosupercharged Lycoming O-540-A1B5, -A1D5, or -A3D5 engines (S/N's 27-1 thru 27-2504).. GE Engine Services-Corporate Aviation Inc. DBA Garrett Aviation Services, Named in the applicability - [STC SA909WE](https://openairdocs.org/stc/SA909WE): Installation of turbosupercharged Lycoming IO-540-J4A5 engines. (PA-E23-250 SN 27-2505 and up). GE Engine Services-Corporate Aviation Inc. DBA Garrett Aviation Services, Named in the applicability - [STC SA978WE](https://openairdocs.org/stc/SA978WE): Installation of turbosupercharged Lycoming O-540-C4B5 engines. Approved for serial numbers 27-2505 and subsequent.. GE Engine Services-Corporate Aviation Inc. DBA Garrett Aviation Services, Named in the applicability --- 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.