AD 86-19-04

86-19-04 DEHAVILLAND: Amendment 39-5398. Applies to all Model DHC-7 series airplanes, certificated in any category. Compliance is required as indicated, unless already accomplished. To ensure detection of heat-damaged wing upper surface structure behind the engine, and protection against wet starts of the engine resulting in external combustion of fuel, accomplish the following:

A. Within three months after the effective date of this AD, perform an external conductivity survey and, as necessary, an internal conductivity survey, and make repairs as necessary, of the upper wing skin behind each engine nacelle, in accordance with the Accomplishment Instructions of DeHavilland Service Bulletin No. 7-57-25, Revision B, dated November 22, 1985. Details of any damage discovered and data obtained from conductivity surveys must be transmitted immediately to DeHavilland Aircraft Company of Canada for processing.

B. For airplanes on which the mid fuel tank access cover located aftof an outboard nacelle has been replaced, within three months after the effective date of this AD, perform an internal conductivity survey of the wing structure in this area and make repairs, as necessary, in accordance with the Accomplishment Instructions of DeHavilland Service Bulletin No. 7-57-25, Revision B, dated November 22, 1985. Following an internal conductivity survey, the removed fuel tank access covers must be inspected before replacement to ensure serviceability, and repaired, if necessary. Details of any damage discovered and data obtained from conductivity surveys must be transmitted immediately to DeHavilland Aircraft Company of Canada for processing.

C. Within 1 year after the effective date of this AD, accomplish DeHavilland Modification No. 7/2414 - "Wing-Upper Skin Structure - Special Inspection and Installation of Heat Shields," described in DeHavilland Service Bulletin No. 7-57-25. The external conductivity survey and, as necessary, the internal conductivity survey detailed in paragraph A., above, must be accomplished immediately prior to installation of Modification 7/2414. For airplanes, serial numbers 1 through 27, Modification Nos. 7/2377 and 7/2378 - "Fuel Tank Access Panel Replacement," described in DeHavilland Service Bulletin No. 7-57-17, must be accomplished prior to the incorporation of Modification No. 7/2414.

D. An alternate means of compliance, which provides an acceptable level of safety, may be used when approved by the Manager, New York Aircraft Certification Office, FAA, New England Region.

E. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base for the accomplishment of inspections and/or modifications required by 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 DeHavilland Aircraft Company of Canada, Downsview, Ontario M3K 1Y5, Canada. These documents may be examined at the FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or FAA, New England Region, New York Aircraft Certification Office, 181 South Franklin Avenue, Room 202, Valley Stream, New York.

This Amendment becomes effective September 26, 1986.