Airworthiness Directive · Amendment 39-11938 · Boeing Model 747 Series Airplanes Equipped with Pratt & Whitney (PW) JT9D-7Q and JT9D-7Q3 Turbofan Engines
Boeing Model 747 Series Airplanes Equipped with Pratt & Whitney (PW) JT9D-7Q and JT9D-7Q3 Turbofan Engines
Model 747 series airplanes, certificated in any category; equipped with Pratt & Whitney JT9D-7Q and JT9D-7Q3 turbofan engines.
Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (c) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that requires a detailed visual inspection to detect evidence of wear or contact between the precooler support fitting and link assembly; and rework and reidentification of the fitting. This amendment is prompted by a report of rupturing of a diffuser case on a PW JT9D-7Q engine due to cracking in the outer pressure wall in the rear skirt area. The actions specified by this AD are intended to prevent contact between the precooler support link and the precooler support fitting, which could contribute to an uncontained failure of the diffuser case and damage to the airplane.
To prevent contact between the precooler support link and the precooler support fitting, which could contribute to an uncontained failure of the diffuser case and damage to the airplane, accomplish the following:
(a) For any precooler support fitting having P/N 65B90924-1 or P/N 65B90924-600 that has not been reworked to the dimensions specified in Boeing Service Letter 747-SL-36-089, dated August 10, 1998: Within 6,000 hours time-in-service after the effective date of this AD, or within 18 months after the effective date of this AD, whichever occurs first, perform a detailed visual inspection to detect evidence of contact wear or contact between the precooler support fitting and link assembly, P/N 69B93162-1 or 69B93162-3, in accordance with the service letter.
(1) If no evidence of contact wear or contact between the precooler support fitting and link assembly is found: At the next engine removal, rework the precooler support fitting to the dimensions specified in the service letter, in accordance with the service letter; and permanently and legibly reidentify the support fitting as P/N 65B90924-601.
(2) If any evidence of contact wear or contact between the precooler support fitting and link assembly is found: Prior to further flight, rework the precooler support fitting to the dimensions specified in the service letter, in accordance with the service letter; and permanently and legibly reidentify the support fitting as P/N 65B90924-601.
Note 2: For the purposes of this AD, a detailed visual inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”
(b) For any precooler support fitting having P/N 65B90924-1 or P/N 65B90924-600 that has been reworked to the dimensions specified in Boeing Service Letter 747-SL-36-089, dated August 10, 1998, but has not been permanently and legibly reidentified: Within 6,000 hours time-in-service or 18 months after the effective date of this AD, whichever occurs first, permanently and legibly reidentify the reworked fitting as P/N 65B90924-601.
