AD 86-12-04

86-12-04 BOEING: Amendment 39-5320. Applies to Model 737 series airplanes, certificated in any category, as listed in Boeing Service Bulletin 737-55-1034, dated April 12, 1985.

To detect cracking in the horizontal stabilizer center section rear spar upper chord, accomplish the following prior to the accumulation of 50,000 landings; or prior to the accumulation of 50,000 landings after chord replacement; or prior to the accumulation of 35,000 landings after modification in accordance with Boeing Service Bulletin 737-55-1034, Part II, dated April 12, 1985; or within 500 landings after the effective date of this AD; whichever occurs latest, unless accomplished within the last 4,000 landings:

A. Eddy current inspect the horizontal stabilizer center section rear spar upper chord for cracks in the areas of each beam gusset plate in accordance with the Flight Safety Inspection Program in Boeing Service Bulletin 737-55-1034, dated April 12, 1985, or later FAA-approved revisions.Repeat the inspections at intervals not to exceed 4,500 landings.

B. If cracks are found in the horizontal stabilizer center section rear spar upper chord, repair in accordance with Part II, or replace in accordance with Part III, of the Accomplishment Instructions in Boeing Service Bulletin 737-55-1034, dated April 12, 1985, or later FAA-approved revisions. Resume the inspections required by paragraph A., above, no later than 9,000 landings after repair, or 50,000 landings after replacement, as appropriate.

C. For purposes of complying with this AD, subject to acceptance by the assigned FAA Maintenance Inspector, the number of landings may be determined by dividing each airplane's hours time in service by the operator's fleet average time from takeoff to landing for the airplane type.

D. 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.

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

All persons affected by this directive who have not already received the appropriate service bulletin from the manufacturer may obtain copies upon request to the Boeing Commercial Airplane Company, P.O. Box 3707, Seattle, Washington 98124. 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 June 30, 1986.