AD 90-20-21

90-20-21 BOEING OF CANADA, LTD., DE HAVILLAND DIVISION: Amendment No. 39-6745. Docket No. 90-NM-69-AD.

Applicability: De Havilland Model DHC-8-100 series airplanes, Serial Numbers 1 through 156 and 158 through 193, certificated in any category.

Compliance: Required within 300 days after the effective date of this AD, unless previously accomplished.

To prevent deformation or loss of the engine forward side cowl doors due to compartment overpressurization, and subsequent loss of fire extinguishing capability, accomplish the following:

A. Modify the cowl door retention latch arrangement and install pressure relief features on both engine cowlings, in accordance with the Accomplishment Instructions in de Havilland Service Bulletin No. 8-71-13, Revision C, dated January 12, 1990.

B. 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, New York Aircraft Certification Office (ACO), ANE-170, FAA, New England Region.

NOTE: The request should be submitted directly to the Manager, New York ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Manager, New York 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 of Canada, Ltd., de Havilland Division, Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplne Directorate, 1601 Lind Avenue S.W., Renton, Washington; or at the FAA, New England Region, New York Aircraft Certification Office, 181 South Franklin Avenue, Room 202, Valley Stream, New York.

This amendment (39-6745, AD 90-20-21) becomes effective on October 26, 1990.