AD 73-25-05

73-25-05 de HAVILLAND: Amendment 39-1750. Applies to DHC-2, MK I (L-20A (U- 6A)) airplanes certificated in all categories.

To prevent hazards in flight associated with fin rear spar attachment bolts and fitting, accomplish the following:

1. This paragraph applies to aircraft that are using AN 7-13 bolts and are or have been operating as floatplanes or amphibians. Within the next 10 hours in service or prior to the next flight carrying loads (e.g. canoes, lumber, etc.) mounted on the float support structure, whichever occurs first, after receipt of this AD, unless accomplished within the last 290 hours in service, perform the following replacements or inspections and at intervals thereafter not to exceed 300 hours.

a. Replace each of the fin rear spar bolts AN 7-13 or remove the bolts and inspect for cracks using a dye penetrant inspection in conjunction with a 10-power glass, or an FAA-approved equivalent inspection. Replace cracked bolts prior to further flight.The repetitive inspection of the bolts may be discontinued upon installation of NAS 147-A26 bolts.

b. Visually inspect the fin rear spar fitting P/N C2TF13, for distortion, cracking, fretting or loose rivets. Replace cracked, distorted or fretted fittings and repair fittings which have loose rivets prior to further flight.

2. Inspect aircraft that are or have been operating as floatplanes or amphibians and are using NAS 147-A26 bolts within the next 10 hours in service or prior to the next flight carrying loads (canoes, lumber, etc.) mounted on the float support structure, whichever occurs first, after receipt of this AD.

a. In accordance with the accomplishment instructions of de Havilland Service Bulletin 2/11 of 6/23/72, or an approved equivalent inspection, unless already accomplished, and

b. Inspect only the fitting in accordance with paragraph 1 above, including the repetitive inspections.

3. Inspect aircraft that have only been operated as landplanes or skiplanes, within the next 100 hours in service after receipt of this AD, unless already accomplished, in accordance with the accomplishment instructions of the service bulletin or an approved equivalent inspection.

4. Where the AD requires replacement or repairs before further flight, the airplane may be flown in accordance with FAR 21.197 to a base where the repair can be performed.

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

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

This amendment is effective December 14, 1973, and was effective upon receipt by all recipients of the airmail dispatch dated September 27, 1973.