AD 83-11-02

83-11-02 BOEING: Amendment 39-4659. Applies to those Model 747 series airplanes certificated in all categories listed in Service Bulletin 747-53-2224, Revision 3, or later FAA approved revisions. To prevent failure of the floor beams and webs, accomplish the following:

A. Visually inspect, or as an alternate, inspect using eddy current inspection techniques, the longitudinal floor beams in the areas noted in the appropriate table of Section III of Boeing Service Bulletin 747-53-2224, Revision 3, or later FAA approved revisions, unless previously accomplished. The inspections are to commence prior to the accumulation of one-half the number of cycles specified in the "Repeat Inspection Interval Cycles" column in the appropriate table in Section III of the service bulletin after the effective date of this AD for airplanes which have accumulated more than the number of cycles listed in the "Inspection Threshold Cycles" column of the table, or prior to accumulating the inspectionthreshold number of cycles, whichever is later. Inspections are to be repeated at intervals not to exceed those specified in the table.

B. Webs or chords found cracked are to be repaired or replaced prior to further flight in accordance with the instructions of Section III of Boeing Service Bulletin 747-53-2224, Revision 3, or later FAA approved revisions, or repair of damaged structure may be deferred as noted therein.

C. Complete modification of the floor beam webs and chords in accordance with the terminating action procedures described in Boeing Service Bulletins 747-53-2224, Revision 3; 747-53-2176, Revision 4; and 747-53-2183, Revision 2; or later FAA approved revisions, constitutes terminating action for this AD.

D. After accomplishing each inspection, repairs, or the terminating modification, apply organic corrosion inhibitor (BMS 3-23) or equal to all exposed floor beams and pressure web structures as required.

E. For purposes of complying with this AD, subject to acceptance by the assigned FAA Principal Maintenance Inspector, the number of landings may be determined by dividing each airplane's hours time in service by the operator's fleet average from takeoff to landing for the airplane type. Only pressurized flights need be considered when establishing number of landings on the airplane.

F. Upon request of the operator, a FAA Principal Maintenance Inspector, subject to prior approval by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, may adjust the inspection interval, if the request contains substantiating data to justify the increase for that operator.

G. Special flight permits may be issued in accordance with Section 21.197 and 21.199 of the Federal Aviation Regulations to operate airplanes to a base for the accomplishment of the inspections and/or modifications required by the AD.

H. Alternate means of compliance or other actions which provide an equivalent level of safety may beused when approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region.

I. This amendment supersedes Airworthiness Directive (AD) 81-13-03, Amendment 39-4138 (46 FR 31873), as amended by Amendment 39-4485 (47 FR 49957).

All persons affected by this directive who have not already received the appropriate service bulletins from the manufacturer may obtain copies upon request to The Boeing Company, P.O. Box 3707, Seattle, Washington 98124. These documents also may be examined at FAA, Northwest Mountain Region, 9010 East Marginal Way South, Seattle, Washington.

This amendment becomes effective June 20, 1983.