AD 90-03-18

90-03-18 BOEING: Amendment 39-6498. Docket No. 88-NM-158-AD.

Applicability: Model 727 and 737 series airplanes, not equipped with a system incorporating Engine Pressure Ratio (EPR) logic for activation of the takeoff warning system, certificated in any category.

Compliance: Required within the next 30 months following the effective date of this AD, unless previously accomplished.

To prevent the occurrence of takeoff configuration nuisance warnings when taxi operations are conducted with the flaps intentionally retracted, accomplish the following:

A. For Boeing Model 727 series airplanes with Auto-Speedbrakes operative: Modify the logic which enables the Takeoff Configuration Warning Systems (TOCWS) in accordance with Boeing Service Bulletin 727- 31-29, January 26, 1979; 727-31-33, dated November 26, 1980; 727-31-35, dated January 26, 1979; or 727-31- 36, dated January 26, 1979, as appropriate.

B. For Boeing Model 727 series airplanes not equipped with Auto-Speedbrakes or with the Auto-Speedbrakes deactivated:

1. Modify the logic which enables the Takeoff Configuration Warning Systems (TOCWS) in accordance with Boeing Service Bulletin 727-31-29, January 26, 1979; 727-31-33, dated November 26, 1980; 727- 31-35, dated January 26, 1979; or 727-31-36, dated January 26, 1979, as appropriate; or

2. Adjust the takeoff warning thrust lever actuated switches to operate at 19.5 degrees from the idle stop for takeoff configuration warning system arming in accordance with Boeing Service Bulletin 727-31-30, dated November 11, 1977. Install a circuit breaker guard (cover) on the TOCWS circuit breaker, and safety wire the guard. Operation of the airplane must be in accordance with the Limitations of the Takeoff Configuration Warning System specified in Appendix 39 or 51 (as appropriate) of the Airplane Flight Manual (AFM).

C. For Boeing Model 737 series airplanes: Modify the logic which enables the TOCWS in accordance with Boeing Service Bulletin 737-31-1033, Revision 1, dated January 14, 1983.

D. 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. NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector (PMI), who will either concur or comment and then send it to the Manager, Seattle Aircraft Certification Office.

E. 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, 17900 Pacific Highway South, Seattle, Washington, or the Seattle Aircraft Certification Office, FAA, Northwest Mountain Region, 9010 East Marginal Way South, Seattle, Washington.

This amendment (39-6498, AD 90-03-18) becomes effective on March 7, 1990.