AD 86-23-01

86-23-01 BOEING: Amendment 39-5450. Applies to all Model 747 series airplanes, certificated in any category, line numbers 1 through 644.

To prevent separation of an engine due to failed H-11 bolts, accomplish the following, unless already accomplished:

A. Prior to accumulation of 10,000 flight hours, or within 100 landings after the effective date of this AD, whichever occurs later, perform a visual inspection of the outboard attach fitting H-11 bolts of all nacelle struts for structural integrity to determine if any H-11 bolts have failed, in accordance with Boeing Service Bulletin 747-57A2235, dated June 27, 1986, or later FAA-approved revisions. Repeat the inspections thereafter at intervals not to exceed 7-1/2 months.

B. Prior to accumulation of 10,000 flight hours, or within 600 landings after the effective date of this AD, whichever occurs later, perform a visual inspection of the inboard attach fitting joints of all nacelle struts for structural integrity to determine if any H-11 bolts have failed, in accordance with Boeing Service Bulletin 747-57A2235, dated June 27, 1986, or later FAA-approved revisions. Repeat the inspections thereafter at intervals not to exceed 15 months.

C. Failed bolts must be replaced prior to further flight.

D. Installation of the Inconel replacement bolts in accordance with Boeing Service Bulletin 747-57A2235, dated June 27, 1986, or later FAA-approved revisions constitutes terminating action for the repetitive inspections required by paragraph A. and B., above.

E. Within 24 months after the effective date of this AD, replace all remaining H-11 bolts on the outboard attach fitting of all nacelle struts with Inconel bolts in accordance with Boeing Service Bulletin 747-57A2235, dated June 27, 1986, or later FAA-approved revisions.

F. Within 48 months after the effective date of this AD, replace all remaining H-11 bolts on the inboard attach fitting of all nacelle struts with Inconel bolts inaccordance with Boeing Service Bulletin 747-57A2235, dated June 27, 1986, or later FAA-approved revisions.

G. An alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office, FAA, Northwest Mountain Region.

H. 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.

I. For the H-11 bolts that utilized the BACN10HR162 nuts, the accomplishment of the inspection requirements of AD 86-05-11 (Amendment 39-5255) is considered an acceptable alternate means of compliance for the initial inspection requirements of paragraph A. and B. of this AD.

NOTE: Inspections performed in accordance with Boeing Service Letter Number 747- SL-57-47, dated April 24, 1986, are considered equivalent to those performed in accordancewith Boeing Service Bulletin 747-57A2235, dated June 27, 1986.

All persons affected by this directive who have not already received the appropriate service document from the manufacturer may obtain copies upon request to the Boeing Commercial Airplane Company, P.O. Box 3707, Seattle, Washington 98124-2207. This document 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 December 1, 1986.