AD 91-09-11

91-09-11 BOEING: Amendment 39-6980. Docket No. 90-NM-240-AD.

Applicability: Model 747 series airplanes, as listed in Boeing Alert Service Bulletin 747- 38A2077, dated August 30, 1990, certificated in any category.

Compliance: Required within 12 months after the effective date of this AD, unless previously accomplished.

To prevent a fire caused by ignition of foreign material in the drain mast internal space, accomplish the following:

A. Install shields to protect the drain mast heater elements in accordance with Boeing Alert Service Bulletin 747-38A2077, dated August 30, 1990.

B. An alternative method 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 forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it tothe Manager, Seattle ACO.

C. 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 Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington.

This amendment (39-6980, AD 91-09-11) becomes effective on May 28, 1991.