# AD 76-20-03: Seal Clearances - Type: Airworthiness directive - Status: Current - Products: Pratt & Whitney Division JT9D-20, JT9D-3A, JT9D-7, JT9D-7A, JT9D-7AH, JT9D-7F and JT9D-7H - Effective: November 16, 1977 - Superseded by: Nothing supersedes this AD - Product type: Engine - Amendment: 39-3070 - Registered aircraft: 18 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/9C80323CF2EB8F9486256E0D00478D83.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/76-20-03 ## The airworthiness directive 76-20-03 PRATT & WHITNEY AIRCRAFT: Amendment 39-2731 as amended by Amendment 39-3070. Applies to all Pratt & Whitney Models JT9D-3A, -7, -7H, -7A, -7AH, -7F and -20 turbofan engines incorporating labyrinth solid land seals P/N's 589733, 589741, 647189 or 729774. I. To prevent possible engine fires due to excessive No. 3 bearing compartment labyrinth seal clearances, accomplish the following: A. Measure the breather air temperature in accordance with Pratt & Whitney Alert Service Bulletin No. 4391, dated February 19, 1975, or later FAA approved revision, or Service Bulletin No. 4703, dated July 1, 1977, or later FAA approved revision, whenever any of the following major engine sections have been or are removed or replaced: 1. Intermediate case. 2. Rear compressor rotor and stator assembly. 3. Rear compressor drive turbine rotor assembly due to: a. Turbine blade root fracture. b. Multiple turbine blade airfoil fracture. c. Failure that causes release of any other rotating part. 4. Front compressor drive turbine rotor assembly due to loss of complete blade. 5. Turbine exhaust case due to loose or missing tailcone. 6. Diffuser case. B. Compare the measured breather air temperature with the limit defined by Pratt & Whitney Curve 4391, for on-ground temperature checks, or Curve 4703, for in-flight temperature checks, and accomplish the following: 1. If the measured breather air temperature is above the limit, remove the engine from service prior to further flight. 2. If the measured breather air temperature is below the limit, accomplish a repetitive temperature check in accordance with the following schedule, or 200 hours after the effective date of this revision, whichever is later: TEMPERATURE MARGIN INSPECTION INTERVAL Less than 5 degrees C 200 hours 5 degrees C but less than 10 degrees C 500 hours 10 degrees C or greater 1000 hours II. To improve the capability of promptly detecting compartment fires, replace main bearing breather tube steel elbow P/N 708237 with magnesium elbow P/N 613265 in accordance with Pratt & Whitney Service Bulletin 4560, dated March 9, 1976, or later FAA approved revision, no later than March 31, 1977. Upon request of the operator, an equivalent method of compliance with the requirements of this AD may be approved by the Chief, Engineering and Manufacturing Branch, Federal Aviation Administration, New England Region. Upon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Engineering and Manufacturing Branch, New England Region, may adjust the 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. The manufacturer's specifications and procedures identified and described in this directive areincorporated 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 these documents from the manufacturer may obtain copies upon request to Pratt & Whitney Aircraft, Division of United Technologies Corporation, 400 Main Street, East Hartford, Connecticut 06108. These documents may also be examined at Federal Aviation Administration, New England Region, 12 New England Executive Park, Burlington, Massachusetts, and at FAA Headquarters, 800 Independence Avenue, S.W., Washington, D.C. A historical file on this AD which includes the incorporated material in full is maintained by the FAA at its headquarters in Washington, D.C., and at New England Region. Amendment 39-2731 supersedes Amendment 39-2109 (40 FR 8544), AD 75-05-16, as amended by Amendment 39-2137 (40 FR 12773). Amendment 39-2731 became effective 30 days after publication in the Federal Register. This amendment 39-3070 becomes effective November 16, 1977. ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS E20EA](https://openairdocs.org/tcds/E20EA): Pratt & Whitney; names 7 of 9 models: JT9D-7, JT9D-7AH, JT9D-3A, JT9D-7F, JT9D-7A, JT9D-20, JT9D-7H ## 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: 18 (0 by airframe model, 18 by engine model) - Makers: Boeing 14, Airbus Industrie 2, Douglas 1, Mcdonnell Douglas 1 Models with the most aircraft: - [Pratt & Whitney JT9D series](https://openairdocs.org/engine/pratt-whitney-jt9d-series): 13 aircraft (engine model) - [Pratt & Whitney JT9D-3A](https://openairdocs.org/engine/pratt-whitney-jt9d-3a): 4 aircraft (engine model) - [Pratt & Whitney JT9D-7](https://openairdocs.org/engine/pratt-whitney-jt9d-7): 1 aircraft (engine model) All 3 models: https://openairdocs.org/ad/76-20-03/models.md Every aircraft: https://openairdocs.org/ad/76-20-03/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.