AD 89-26-07 ACTIVE

89-26-07 BOEING OF CANADA, LTD., DE HAVILLAND DIVISION: Amendment 39-6422. Docket No. 89-NM-161-AD.

Applicability: All Model DHC-7 series airplanes, certificated in any category.

Compliance: Required as indicated, unless previously accomplished.

To prevent reduced structural capability of the fuselage and subsequent decompression of the airplane, accomplish the following:

A. Within 60 days after the effective date of this AD, perform the following inspections and repair, in accordance with de Havilland Service Bulletin 7-53-33, Revision A, dated June 9, 1989:

1. Perform a low frequency ultrasonic inspection for disbonding of the fuselage belly skin doublers, between fuselage stations X248.00 and X535.25 below stringer 20 left and right, in accordance with Inspection Part A of the service bulletin.

2. Visually inspect for looseness or working of the rivets in the vertical skin joints, at fuselage stations X535.25 and X576.25 below stringer 20, leftand right.

3. Visually inspect for looseness or working of the rivets in the fuselage skin joints at station X630.00 around the complete periphery of the fuselage, above and below the passenger and emergency exit doors.

4. Visually inspect for looseness or working of the rivets in the skin longitudinal joint between fuselage stations X424.00 to X484.00 along stringer 20, left and right. Pay particular attention to the lower line of rivets.

5. Repair all loose rivets prior to further flight, in a manner approved by the Manager, New York Aircraft Certification Office, ANE-170, FAA, New England Region.

6. Repair all disbonding prior to further flight, in accordance with the service bulletin.

B. Within 90 days after the effective date of this AD:

1. Perform a low frequency ultrasonic inspection for disbonding of the fuselage left and right sidewall skin doublers, between fuselage stations X248.00 and X596.75, between stringer 20 and 10, in accordance withde Havilland Service Bulletin 7-53-33, Revision A, dated June 9, 1989.

2. Repair any disbonding prior to further flight, in accordance with the service bulletin.

C. Within 150 days after the effective date of this AD:

1. Perform a low frequency ultrasonic inspection for disbonding of the fuselage roof skin doublers between fuselage stations X248.00 and X630.00, between stringer 10, left and right, in accordance with de Havilland Service Bulletin 7-53-33, Revision A, dated June 9, 1989.

2. Repair any disbonding prior to further flight, in accordance with the service bulletin.

D. Within 3 days after accomplishing each of the inspections required by paragraphs A., B., and C., above, report all findings, positive or negative, to the Director, Airworthiness Branch, Transport Canada, Ottawa, Canada; to the manufacturer, Boeing of Canada, Ltd., de Havilland Division, in accordance with de Havilland Service Bulletin 7-53-33, Revision A, dated June 9, 1989; and to the FAA, Manager, New York Aircraft Certification Office, ANE-170, New England Region.

E. 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, ANE-170, FAA, New England 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, New York Aircraft Certification Office, ANE-170.

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 of Canada, Ltd., de Havilland Division, Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. These documents may beexamined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 17900 Pacific Highway South, Seattle, Washington, or New York Aircraft Certification Office, FAA, New England Region, 181 South Franklin Avenue, Valley Stream, New York.

This amendment (39-6422, AD 89-26-07) becomes effective on January 14, 1990.