# AD 71-24-05: Compressor Rotor Discs - Type: Airworthiness directive - Status: Current - Products: Pratt & Whitney Division JFTD12A-4A (T73P-1), JFTD12A-5A (T73-P-700), JT12A-6, JT12A-6A and JT12A-8 - Effective: May 31, 1974 - Superseded by: Nothing supersedes this AD - Product type: Engine - Amendment: 39-1847 - Registered aircraft: 52 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/97CBE833497C373886256E01005AD841.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/71-24-05 ## The airworthiness directive 71-24-05 PRATT & WHITNEY: Amendment 39-1137 as amended by Amendment 39-1847. Applies to all Pratt & Whitney Aircraft JT12A series turbojet and JFTD12A series turboshaft engines which incorporate any of the compressor rotor discs with serial numbers listed in Pratt & Whitney Aircraft Turbojet Engine Service Bulletin No. 3421 dated 4 August 1971 as amended by Revision No. 3, dated December 10, 1973. Compliance required as indicated. (a) To preclude compressor rotor disc failure as the result of reduced life from traces of lead - (1) For those discs listed in Pratt & Whitney Aircraft turbojet Engine Service Bulletin No. 3421, dated August 4, 1971, remove from service the listed discs prior to reaching the revised life limit or within the next 30 cycles in service after November 26, 1971, whichever comes later. (2) For those discs not listed in the above Service Bulletin but listed in Revision No. 3, dated December 10, 1973, remove from service the listed discs prior to reaching the revised life limit or within the next 30 cycles in service after the effective date of this amendment, whichever comes later. The manufacturer's Service Bulletin identified and described in this directive is incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive who have not already received this document from the manufacturer may obtain copies upon request from Pratt & Whitney Aircraft Division of United Aircraft Corporation, East Hartford, Connecticut 06108. This document may also be examined at the FAA, New England Region, 12 New England Executive Park, Burlington, Massachusetts or at the FAA Headquarters, 800 Independence Avenue, S.W., Washington, D.C. A historical file on the AD which includes the incorporated material in full is maintained by the FAA in its headquarters in Washington, D.C., and in the New England Region. Upon submission of substantiating data through an FAA Maintenance Inspector by an owner or operator to the Chief, Engineering and Manufacturing Branch, FAA New England Region, compliance time may be adjusted. The incorporation by reference provision in this document was approved by the Director of the Federal Register on June 19, 1967. Amendment 39-1337 was effective November 26, 1971. This Amendment 39-1847 becomes effective May 31, 1974. ## Affected data sheets (2) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS 1E9](https://openairdocs.org/tcds/1E9): Erickson Incorporated DBA Erickson Air-Crane; names 3 of 4 models: JT12A-6A, JT12A-6, JT12A-8 - [TCDS E15EA](https://openairdocs.org/tcds/E15EA): Erickson Incorporated DBA Erickson Air-Crane; names 2 of 2 models: JFTD12A-4A (T73P-1), JFTD12A-5A (T73-P-700) ## 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: 52 (0 by airframe model, 52 by engine model) - Makers: Sikorsky 18, North American 8, Erickson 5, Helicopter Transport Services 5, Rockwell International 5, Aerovodochody 3, Siller Helicopters 3, Aero Vodochody 1, Aviation International Rotors 1, Erickson Air Crane 1 Models with the most aircraft: - [Pratt & Whitney JFTD12A series](https://openairdocs.org/engine/pratt-whitney-jftd12a-series): 15 aircraft (engine model) - [Pratt & Whitney JFTD12A-4A](https://openairdocs.org/engine/pratt-whitney-jftd12a-4a): 12 aircraft (engine model) - [Pratt & Whitney JT12A-8](https://openairdocs.org/engine/pratt-whitney-jt12a-8): 12 aircraft (engine model) - [Pratt & Whitney JFTD12A-5A](https://openairdocs.org/engine/pratt-whitney-jftd12a-5a): 8 aircraft (engine model) - [Pratt & Whitney JT12A series](https://openairdocs.org/engine/pratt-whitney-jt12a-series): 3 aircraft (engine model) - [Pratt & Whitney JT12A-6](https://openairdocs.org/engine/pratt-whitney-jt12a-6): 2 aircraft (engine model) All 6 models: https://openairdocs.org/ad/71-24-05/models.md Every aircraft: https://openairdocs.org/ad/71-24-05/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.