AD 87-04-23 ACTIVE

87-04-23 DeHAVILLAND: Amendment 39-5548. Applies to Model DHC-6-1, DHC-6- 100, DHC-6-200, and DHC-6-300 (all serial numbers) airplanes certificated in any category.

Compliance: Required as indicated, after the effective date of this AD, unless already accomplished.

To prevent failure of the wing support struts due to corrosion, accomplish the following:

(a) Visually inspect each wing support strut for corrosion in accordance with the "ACCOMPLISHMENT INSTRUCTIONS" in DeHavilland Service Bulletin (S/B) No. 6/474, dated June 14, 1985, Revision A, dated March 28, 1986, as follows:

(1) For aircraft that have accumulated 5,000 or more hours time-in-service (TIS) or are four and one half or more years old on the effective date of this AD, accomplish the inspection within the next 1,000 hours TIS or six months, whichever occurs first, after the effective date of this AD.

(2) For aircraft that have accumulated less than 5,000 hours TIS and are less than four andone half years old on the effective date of this AD, accomplish the inspection before the accumulation of 6,000 hours TIS or five years, whichever occurs first.

(3) For all airplanes, reinspect at intervals not to exceed 6,000 hours TIS or five years, whichever occurs first, following the previous inspection accomplished in accordance with this AD.

(b) If the inspections specified in paragraph (a) of this AD show moderate or severe corrosion anywhere on the wing support struts, or any corrosion within 20 inches from either end of the wing support struts, replace the affected support strut prior to further flight.

(c) If the inspections specified in paragraph (a) of this AD show light corrosion in areas other than 20 inches from either end of the struts, remove the corrosion within 30 days.

NOTE: Advisory Circular (AC) 43-4, discusses corrosion evaluation, degree of damage, and rework procedures.

(d) An alternate method of compliance, which provides an equivalent level of safety, may be used if approved by the Manager, New York Aircraft Certification Office, FAA, New England Region, 181 South Franklin Avenue, Valley Stream, New York 11581.

(e) Airplanes may be flown in accordance with FAR 21.197 to a location where this AD may be accomplished.

(f) Upon submission of substantiating data by an owner or operator, through an FAA Maintenance Inspector, the Manager, New York Aircraft Certification Office, FAA, New England Region, may adjust the compliance times in this AD.

All persons affected by this directive may obtain copies of the document referred to herein upon request to The DeHavilland Aircraft Company of Canada, A Division of Boeing of Canada, Ltd., Garratt Boulevard, Downsview, Ontario, Canada M3K 1Y5; or FAA, Office of the Regional Counsel, Room 1558, 601 East 12th Street, Kansas City, Missouri 64106.

This amendment becomes effective on March 16, 1987.