AD 90-05-03

90-05-03 BOEING OF CANADA, LTD., DE HAVILLAND DIVISION: Amendment 39- 6520. Docket No. 89-NM-236-AD. Applicability: de Havilland Model DHC-8-300 series airplanes, Serial Numbers 100 through 231, inclusive, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent possible rupture of the engine bleed air ducts, accomplish the following:

A. Within the next 50 hours time-in-service after the effective date of this AD, and thereafter at intervals not to exceed 50 hours time-in-service, perform a visual inspection to detect cracks or complete separation of the bleed air precooler mounting lugs, in accordance with de Havilland Alert Service Bulletin A8-21-32, Revision A, dated November 22, 1989.

B. If cracks are found in more than one lug, or if any lug has completely separated, repair prior to further flight, in accordance with de Havilland Alert Service Bulletin A8-21-32, Revision A, dated November 22, 1989.C. 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, Standardization Branch, ANM-113, 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, Standardization Branch, ANM-113.

D. 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 of Canada, Ltd., de Havilland Division, Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. This information may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South,Seattle, Washington, or at the FAA, New England Region, New York Aircraft Certification Office, 181 South Franklin Avenue, Room 202, Valley Stream, New York 11581.

This amendment (39-6520, AD 90-05-03) becomes effective on April 6, 1990.