SAIB ACE-96-15

SPECIAL

AIRWORTHINESS

INFORMATION

BULLETIN

AIRCRAFT CERTIFICATION SERVICE 800 INDEPENDENCE AVENUE, S.W.

WASHINGTON, DC 20591

U.S. Department of Transportation Federal Aviation Administration

No. ACE-96-15 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 Informati on Bulletin is to advise registered owners of certain de Havilland airplanes of the need to insp ect horizontal and vertical stabilizer attachment fittings.

This Bulletin is being sent to registered owne rs of de Havilland models DHC-6-1, -100, -200, and -300 Twin Otter airplanes.

BACKGROUND:

The Federal Aviation Administration (FAA) has received service difficulty reports concerning corrosion and cracking of the fuselage horizontal stabilizer rear attachment adapter on airplanes which have been operated in severe environmen ts. Corrosion was found during routine inspection, but the extent of the corrosion was not readily vi sible. The manufacturer has created a service bulletin to introduce additional inspection proce dures to detect corrosion and cracking due to long-term environmental exposure. The FAA po licy on aging commuter class airplanes is to eliminate or, in certain instances, to reduce th e number of repetitive inspections when improved parts or modifications are available. In this in stance, additional inspections have been determined to be most effective in correcting the discrepant condition.

RECOMMENDATION:

The FAA is recommending, but not requiring, that:

(A) Owners/operators of de Havilland models DHC -6-1, -100, -200, and -300 Twin Otter airplanes perform additional structural inspections in accordance with de Havilland service bulletin no. 6/454, Inspection Part A, to detect corrosion or cracking, and (B) If any corrosion is found as a result of the above Part A inspection, perform additional inspections in accordance with Inspection Part B of bulletin 6/454 within 200 flight hours.

(C) If any cracking is found as a result of the above Part A inspection, perform additional inspections in accordance with Inspection Part B of bulletin 6/454 before further flight.

NOTE: Inspection Part A will require approxima tely 4 workhours to accomplish, and Inspection Part B will require approximately 40 workhours to complete.

FOR FURTHER INFORMATION CONTACT:

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