AD 90-15-17

90-15-17 BOEING: Amendment 39-6673. Docket No. 89-NM-210-AD.

Applicability: Model 737 series airplanes, as listed in Boeing Alert Service Bulletin 737- 28A1072, dated August 27, 1987, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent engine fuel starvation resulting from main wing tank suction feed system stress fractures or fuel boost pump bypass valve freezing, accomplish the following:

A. Prior to the accumulation of 150 flight hours after January 27, 1988 (the effective date of Amendment 39-5823, AD 88-01-06), and thereafter at intervals not to exceed 300 flight hours, perform an operational test of the bypass valves in accordance with Boeing Alert Service Bulletin 737-28A1072, dated August 27, 1987.

B. The operational tests required by paragraph A., above, may be terminated when the fuel system modifications, detailed in Boeing Service Bulletin 737-28A1072, Revision 2, dated February 18, 1988, or Revision 3, dated October 6, 1988, are installed.

C. For airplanes modified in accordance with paragraph B., above: Within one year after the effective date of this amendment, conduct an inspection of the suction feed bypass system for preloading in accordance with Boeing Alert Service Bulletin 737-28A1072, Revision 4, dated August 7, 1989. If preloading is discovered in the suction feed bypass system, prior to further flight, modify in accordance with that service bulletin.

D. For all other airplanes: Within one year after the effective date of this amendment, modify the fuel boost pump bypass valves system in accordance with Boeing Alert Service Bulletin 737-28A1072, Revision 4, dated August 7, 1989. This modification constitutes terminating action for the repetitive operational tests required by paragraph A., above.

E. An alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approvedby 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 then 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 documents from the manufacturer may obtain copies upon request to Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or Seattle Aircraft Certification Office, 9010 East Marginal Way South, Seattle, Washington.

This AD supersedes AD 88-01-06 R1, Amendment 39-5990. This amendment (39-6673, AD 90-15-17) becomes effective on August 27, 1990.