AD 74-22-06

74-22-06 DEHAVILLAND: Amendment 39-1993. Applies to DHC-6 airplanes Serial Numbers 1 to 393 inclusive, excluding Serial Numbers 107, 168, 182, 184, 209, 383, 385, 386, 390 and 391, certificated in all categories.

To detect cracks in the horizontal stabilizer rear spars, within the next 50 hours in service or 1 week, whichever occurs first, after the effective date of this AD, unless already accomplished, inspect visually using a magnification glass of at least 10 power or an approved equivalent for spanwise cracks along the radii at the junctions of the rear spar webs with the top and bottom flanges between Station 10.00 and Station 53.00 on the left and right hand horizontal stabilizers.

If cracks are found, accomplish the following:

1. Alter the spar in accordance with paragraph 2 of Accomplishment Instructions of de Havilland Service Bulletin No. 6/310, dated June 28, 1974, or an approved equivalent before further flight, except that the airplane may be flown inaccordance with FAR 21.197 to a base where the alteration can be performed.

2. Equivalent inspections or alterations must be approved by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region.

3. The compliance times may be increased by the Chief, Engineering and Manufacturing Branch, FAA, Eastern Region, upon receipt of substantiating data submitted through an FAA maintenance inspector.

This amendment is effective October 23, 1974.