Airworthiness Directive · Amendment 39-16483 · Nacelles/pylons
McDonnell Douglas Corporation Model MD-90-30 Airplanes
This AD applies to McDonnell Douglas Corporation Model MD-90-30 airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin MD90-54A003, Revision 2, dated February 12, 2010.
We are superseding an existing airworthiness directive (AD) for the products listed above. That AD currently requires a detailed inspection for certain defects of the upper fasteners of the aft mount support fittings of the left and right engines, and corrective actions if necessary. This new AD requires repetitive replacement of the upper row of fasteners of the support fittings of the engine aft mount with new fasteners; and repetitive general visual inspections for defects of the lower row fasteners (Row B) of the support fittings of the left and right engine aft mounts, and replacement of all clearance fit fasteners in the lower row if necessary. This AD was prompted by reports of loose, cracked, or missing fasteners in the aft mount support fitting of the left and right engines. We are issuing this AD to prevent loose, cracked, or missing fasteners in the engine aft mount support fittings, which could lead to separation of the support fittings from the pylon, and could result in separation of the engine from the airplane.
You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.
Except as required by paragraph (i) of this AD, at the applicable time specified in paragraph 1.E., “Compliance,” of Boeing Alert Service Bulletin MD90-54A003, Revision 2, dated February 12, 2010: Replace the upper row of fasteners (Row A) of the support fittings of the left and right engine aft mounts with new fasteners, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-54A003, Revision 2, dated February 12, 2010. Repeat the replacement thereafter at intervals not to exceed 10,000 flight cycles.
(h) Concurrently with any replacement required by paragraph (g) of this AD: Perform a general visual inspection for defects of the lower row fasteners (Row B) of the support fittings of the left and right engine aft mounts, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-54A003, Revision 2, dated February 12, 2010. Defects include missing, loose, and damaged fasteners.
(1) If no defect is found during any general visual inspection required by paragraph (h) of this AD, before further flight, insert a 0.0015-inch feeler gauge between the washer and the structure, or between the fastener head and structure, as applicable, to detect a gap condition, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-54A003, Revision 2, dated February 12, 2010. A gap condition is a defect identified in any location where the feeler gauge can slip completely between a washer or a fastener head and the structure.
(i) If no defect is found during any gap check required by paragraph (h)(1) of this AD, before further flight, apply torque to the fasteners of the lower row (Row B) to determine if there is a defect, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-54A003, Revision 2, dated February 12, 2010. A defect is any fastener that turns with the application of the specified torque. If any defect is found, before further flight, replace all clearance fit fasteners in the lower row (Row B), in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-54A003, Revision 2, dated February 12, 2010.
(ii) If any defect is found during any gap check required by paragraph (h)(1) of this AD, before further flight, replace all clearance fit fasteners in the lower row (Row B), in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-54A003, Revision 2, dated February 12, 2010.
(2) If any defect is found during any general visual inspection required by paragraph (h) of this AD, before further flight, replace all clearance fit fasteners in the lower row (Row B), in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin MD90-54A003, Revision 2, dated February 12, 2010.
(i) Where Boeing Alert Service Bulletin MD90-54A003, Revision 2, dated February 12, 2010, specifies a compliance time after the original issue date on the service bulletin, this AD requires compliance within the specified compliance time after the effective date of this AD.
Replacements and inspections accomplished before the effective date of this AD in accordance with Boeing Alert Service Bulletin MD90-54A003, Revision 1, dated November 17, 2009, are considered acceptable for compliance with the corresponding actions required by this AD.
