AD 86-08-03

86-08-03 BOEING: Amendment 39-5289. Applies to Model 747 series airplanes equipped with General Electric CF6-50 and Pratt and Whitney JT9D-70A engines, listed in Boeing Service Bulletin 747-54A2117, Revision 1, dated November 8, 1985, certificated in any category. To prevent failure of the outboard engine strut aft diagonal brace, accomplish the following, unless already accomplished:

A. Within the next 200 landings after the effective date of this AD, perform a close visual (detailed) inspection for cracking in the brace, and install sealant backup plates and heat resistant sealant over the firewall openings in the strut lower aft bulkhead, in accordance with Boeing Service Bulletin 747-54A2117, Revision 1, or later FAA-approved revisions. Repeat the close visual (detailed) inspection at intervals not to exceed 200 landings until the inspection required by paragraph B., below, is accomplished.

NOTE: Definition of close visual (detailed) inspection method: Close intensive visual inspections of highly defined structural details or locations searching for evidence of structural irregularity. Using adequate lighting and, where necessary, inspection aids such as mirrors, etc., surface cleaning and access procedures may be required to gain proximity.

B. Within the next 400 landings after the effective date of this AD, perform an eddy current conductivity test of the strut diagonal brace to determine its heat treat temper condition in accordance with Boeing Service Bulletin 747-54A2117, Revision 1, or later FAA-approved revisions. Repeat the close visual (detailed) inspection of the strut diagonal brace for cracking specified in paragraph A., above.

C. If the strut diagonal brace conductivity readings indicate an acceptable brace, as defined by Boeing Service Bulletin 747-54A2117, Revision 1, or later FAA-approved revisions, and no cracks are found, no further action is required relative to the diagonal brace.

D. If the strut diagonal brace conductivity readings indicate a possible unacceptable brace, and no cracks are found, visually reinspect the brace lugs for cracks at intervals not to exceed 200 landings until the actions required by paragraph E. of this AD are accomplished.

E. If the strut diagonal brace conductivity readings indicate a possible unacceptable brace, and no cracks are found, accomplish the strut diagonal brace strength verification (Rockwell Hardness Testing) and any necessary corrective action, in accordance with Boeing Service Bulletin 747-54A2117, Revision 1, or later FAA-approved revisions, as follows:

1. within 2,000 landings for airplanes that have accumulated less than 3,000 landings;

2. within 1,500 landings for airplanes that have accumulated 3,000 to 6,000 landings; and

3. within 1,000 landings for airplanes that have accumulated over 6,000 landings.

F. Cracked parts must be replaced prior to further flight.

G. Upon request of an operator, an FAA PrincipalMaintenance Inspector, subject to prior approval of the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, may adjust the inspection times specified in this AD to permit compliance at an established inspection period of that operator, if the request contains substantiating data to justify the change for that operator.

H. Alternate means of compliance which provide an acceptable level of safety may be used when approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region.

I. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base for the accomplishment of inspections and/or modifications required by this AD.

All persons affected by this proposal who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to the Boeing Commercial Airplane Company, P.O. Box 3707, Seattle, Washington 98124-2207. These documents may be examined at the FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or the Seattle Aircraft Certification Office, 9010 East Marginal Way South, Seattle, Washington.

This amendment becomes effective May 27, 1986.