Airworthiness Directive · Amendment 39-11590 · Boeing Model 737-200C Series Airplanes
Boeing Model 737-200C Series Airplanes
Model 737-200C series airplanes having line numbers 292 and subsequent, certificated in any category.
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 (e) 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) that is applicable to certain Boeing Model 737-200C series airplanes. This action requires repetitive inspections to detect cracking in the lower skin at the stringer 4R lap joint, and certain fuselage frames; and corrective actions, if necessary. This amendment also provides for optional terminating action for the repetitive inspections. This amendment is prompted by a report of a fractured frame located at body station (BS) 480. The actions specified in this AD are intended to detect and correct cracking in certain frames, which, in conjunction with multiple site cracking in the lower skin of the lap joint, could result in failure of certain lap joints, and consequent rapid decompression of the airplane fuselage.
To detect and correct cracking in certain fuselage frames, which, in conjunction with multiple site cracking in the lower skin of the lap joint, could result in failure of certain lap joints, and consequent rapid decompression of the airplane fuselage, accomplish the following:
(a) Prior to the accumulation of 50,000 total flight cycles, or within 600 flight cycles after the effective date of this AD, whichever occurs later: Perform a low frequency eddy current (sliding probe) inspection to detect cracking in accordance with Part 3.A. of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1220, dated October 4, 1999. Repeat the inspections at intervals not to exceed 600 flight cycles until accomplishment of the requirements of paragraph (b) of this AD.
(b) Within 2,500 flight cycles following accomplishment of the initial inspection required by paragraph (a) of this AD: Perform an internal detailed visual inspection to detect cracking in accordance with the Part 3.B. of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1220, dated October 4, 1999. Repeat the inspection thereafter at intervals not to exceed 2,500 flight cycles until the modification required by paragraph (d) of this AD is accomplished.
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.”
(c) Prior to further flight, repair any cracking detected by any inspection required by paragraph (a) or (b) of this AD in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate; or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative (DER) who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD.
(d) Installation of the preventative modification of the BS 480 frame in accordance with Part 3.C. of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-53A1220, dated October 4, 1999, constitutes terminating action for the requirements of this AD.
