Airworthiness Directive · Amendment 39-11717 · Boeing Model 747-100, -200, 747SP, and 747SR Series Airplanes Equipped With Pratt & Whitney JT9D-7, -7A, -7F, and -7J Series Engines
Boeing Model 747-100, -200, 747SP, and 747SR Series Airplanes Equipped With Pratt & Whitney JT9D-7, -7A, -7F, and -7J Series Engines
Model 747-100, -200, 747SP, and 747SR series airplanes; certificated in any category; equipped with Pratt & Whitney JT9D-7, -7A, -7F, and -7J series 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 747-100, -200, 747SP, and 747SR series airplanes, that requires one-time detailed visual and eddy current inspections to detect cracking of the nose cowl mounting flange; rework of the nose cowl mounting flange; eddy current inspection to detect cracking of the reworked nose cowl mounting flange; and corrective action, if necessary. This amendment is prompted by reports of the nose cowl separating from the engine and departing the airplane following severe engine vibration. The actions specified by this AD are intended to prevent separation of the nose cowl from the engine, which could cause collateral damage to the airplane, and, possibly, reduced controllability of the airplane.
To prevent separation of the nose cowl from the engine, which could cause collateral damage to the airplane, and, possibly, reduced controllability of the airplane, accomplish the following:
(a) Within 24 months after the effective date of this AD, perform one-time detailed visual and eddy current inspections to detect cracking of the existing nose cowl mounting flange, rework the nose cowl mounting flange to increase the number of attachment fastener holes from 37 to 67, and perform a one-time eddy current inspection to detect cracking of the new fastener holes in the reworked nose cowl mounting flange, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-71-2290, dated March 18, 1999.
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 aides such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”
(b) If any crack is found during any inspection required by paragraph (a) of this AD: Prior to further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate.
