AD 90-17-20

90-17-20 BOEING: Amendment 39-6707. Docket No. 90-NM-150-AD.

Applicability: Model 737 series airplanes, listed in Boeing Alert Service Bulletin 737- 57A1079, Revision 4, dated May 10, 1990, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent the loss of the outboard flap, accomplish the following:

A. Within the next 250 hours time-in-service after the effective date of this AD, unless already accomplished within the last 750 hours time-in-service, and thereafter at intervals not to exceed 1,000 hours time-in-service from the last inspection, accomplish a torque check of the 5/16-inch bolts that attach the forward support fitting of the inboard and outboard flap tracks of the outboard flap, in accordance with Boeing Alert Service Bulletin 737-57A1079, Revision 4, dated May 10, 1990.

B. Bolts which either fail or do not sustain the torque check must be replaced prior to further flight, in accordance with Boeing Service Bulletin 737-57A1079, Revision 4, dated May 10, 1990.

1. If the replacement bolt is a 5/16-inch bolt, accomplish the torque check required by paragraph A. of this AD prior to the accumulation of 5,000 hours time-in-service, and thereafter at intervals not to exceed 1,000 hours time-in-service from the last inspection.

2. If the replacement bolt is a 3/8-inch stainless steel bolt, no further torque checks, in accordance with this AD, are necessary.

D. Replacement of 5/16-inch diameter bolts with 3/8-inch diameter stainless steel bolts, in accordance with Boeing Alert Service Bulletin 737-57A1079, Revision 4, dated May 10, 1990, or earlier revisions, constitutes terminating action for the requirements of this AD.

E. 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 (ACO), FAA, Transport Airplane Directorate.

NOTE: The request should be submitted directly to the Manager, Seattle ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will than forward comments or concurrence to the Seattle ACO.

F. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD.

All persons affected by this directive who have not already received the appropriate service information from the manufacturer may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue, S.W., Renton, Washington.

Airworthiness Directive 90-17-20 supersedes AD 74-19-05, Amendment 39-1958. This amendment (39-6707, AD 90-17-20) becomes effective on September 4, 1990.