SAIB ACE-96-14 —

No. ACE-96-14 December 20, 1996

Published by: FAA, AFS-610, P.O. Box 26460, Oklahoma City, OK 73125 This is issued for informational purposes only and any recommendation for corrective action is not mandatory.

INTRODUCTION: The purpose of this Special Airworthiness Information Bulletin is to inform registered owners of certain de Havilland airplanes of the need to inspect for corrosion at certain wing lower skin rivets. This Bulletin is being sent to registered owners of de Havilland models DHC-6 airplanes, serial numbers 1 through 230 inclusive.

BACKGROUND: The Federal Aviation Administration (FAA) has received service difficulty reports concerning corrosion on rivets attaching the wing lower skin to the front wing spar flange between the landing light and the engine nacelle. The corrosion results from deterioration of the original surface finish, engine exhaust deposits, environmental effects, and infrequent cleaning of the affected area. If undetected, the corrosion could result in loss of the rivets, and consequent loss of integrity of the joint and reduction in wing fatigue life.

RECOMMENDATION: The FAA is recommending, but not requiring, that: (A) Owners/operators of de Havilland models DHC-6 airplanes, serial numbers 1 through 230, inspect for corrosion at the rivets which attach the wing lower skins to the front spar between the landing lights and the engine nacelles in accordance with the compliance section of de Havilland service bulletin no. 6/351. (B) For airplanes with less than 10,000 flight hours, inspect in accordance with Accomplishment Instructions, Part A, and replace any defective or missing rivets and restore protective finish. (C) For airplanes with more than 10,000 flight hours, inspect in accordance with Accomplishment Instructions, Part B, which requires additional disassembly to complete the necessary inspections.

NOTE: Approximately 3 workhours will be required to accomplish the basic inspection.

FOR FURTHER INFORMATION CONTACT: Federal Aviation Administration, New York Aircraft Certification Office, 10 Fifth St., Third Floor, Valley Stream, NY 11581, Attention: Jon Hjelm, telephone (516) 256-7523, facsimile (516) 568-2716.