AD 91-09-08 ACTIVE

91-09-08 BOEING OF CANADA, LTD., DE HAVILLAND DIVISION: Amendment 39- 6975. Docket No. 90-NM-275-AD. Supersedes AD 80-22-14.

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

Compliance: Required as indicated, unless previously accomplished.

To prevent structural fatigue failure of the fuselage longeron at the rear spar frame and the lower wing/outboard nacelle joint, accomplish the following:

A. For airplanes Serial Numbers 1 through 14, with 2,975 hours or more time-in- service: Within the next 25 hours time-in-service, after October 31, 1980 (the effective date of Amendment 39-3961, AD 80-22-14), unless previously accomplished within the last 975 hours time-in-service, perform a radiographic inspection for cracks at the rear spar wing attachment to the fuselage frame in accordance with the instructions given in Figures 1 and 2 of de Havilland Service Bulletin 7-53-9, dated May 23, 1980.

NOTE: Inspections performed in accordance with de Havilland Service Bulletin 7-53-9, Revision A, dated June 9, 1980, or Revision B, dated September 10, 1982, are considered in compliance with the requirements of this paragraph.

1. If cracks are found, prior to further flight, repair in a manner approved by the Manager, New York Aircraft Certification Office (ACO), ANE-170, FAA, New England Region, and incorporate de Havilland Modification No. 7/1622 (reinforcement of the rear spar frame) in accordance with the Accomplishment Instructions of the service bulletin.

2. If no cracks are found, repeat the radiographic inspection at intervals not to exceed 1,000 hours time-in-service.

B. For airplanes Serial Numbers 1 through 14 and 17, with 4,975 hours or more time-in-service: Within the next 25 hours time-in-service, after October 31, 1980 (the effective date of Amendment 39-3961, AD 80-22-14), unless previously accomplished within the last 975 hours time-in-service, perform a radiographic inspection for cracks at the wing/outboard nacelle joint in accordance with the instructions given in Figure 1 of DeHavilland Service Bulletin 7-57- 4, dated May 23, 1980.

NOTE: Inspections performed in accordance with de Havilland Service Bulletin 7-57-4, Revision A, dated September 10, 1982, are considered in compliance with the requirements of this paragraph.

1. If cracks are found, prior to further flight, repair in a manner approved by the Manager, New York Aircraft Certification Office (ACO), ANE-170, FAA, New England Region, and incorporate DeHavilland Modification No. 7/1645 (reinforcement of the lower wing structure and outboard nacelle) in accordance with the Accomplishment Instructions of the service bulletin.

2. If no cracks are found, repeat the radiographic inspection at intervals not to exceed 1,000 hours time-in-service.

C. Within 2 years after the effective date of this AD, reinforce the longeron at the rear spar frame (Modification No. 7/1622) and reinforce the wing/nacelle joint (Modification No. 7/1645), in accordance with the Accomplishment Instructions in de Havilland Service Bulletins 7-53-9, Revision B, and 7-57-4, Revision A, both dated September 10, 1982. Accomplishment of Modifications 7/1622 and 7/1645 constitutes terminating action for the repetitive radiographic inspections required by paragraphs A. and B. of this AD.

D. 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, Standardization Branch, ANM-113, 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 to the Manager, Standardization Branch, ANM-113.

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 of Canada, Ltd., de Havilland Division, Garratt Boulevard, Downsview, Ontario, Canada M3K 1Y5. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington, or at the FAA, New England Region, New York Aircraft Certification Office, 181 South Franklin Avenue, Valley Stream, New York.

Airworthiness Directive 91-09-08 supersedes AD 80-22-14, Amendment 39-3961.

This amendment (39-6975, AD 91-09-08) becomes effective on May 28, 1991.