AD 54-20-02

54-20-02 SIKORSKY: Applies to All Model S-55 Helicopters.

Compliance required as indicated.

In order that cracks in the fore and aft transmission support assemblies (S14-20-2503) may be detected, these assemblies should be inspected daily, without removing the support assemblies from the helicopter, in accordance with the following procedure:

1. Remove the paint, grease and foreign matter from all welds and from the areas of the tubes within 3 inches of a weld on both upper and lower ends.

2. Inspect for cracks all areas of the tubes within 2 inches of a weld and all welds visually, and, where possible, with the assistance of a 5- to 7-power glass.

3. Assemblies found with a crack should be replaced immediately.

4. Protect the exposed areas of metal with any suitable corrosion preventive.

The manufacturer is presently investigating the reasons for the occurrence of such cracks and a permanent repair is expected in the near future which, when incorporated, will make these daily inspections unnecessary. These inspections are in addition to those required by AD 54-16- 01.

(Revision C to Sikorsky Information Circular No. 1435-383 covers this same subject.)

When transmission support, S14-20-4603, is installed in place of support S14-20-2503, the above inspection may be performed at every intermediate inspection rather than on a daily basis.

(Sikorsky Service Information Circular No. 1420-548, dated December 3, 1954, covers the installation instructions.)