54-16-01 SIKORSKY: Applies to All Model S-55 Helicopters.
Compliance required as indicated.
1. (a) The rear accessory covers of main transmission S14-35-4000 and S14- 35-4300 should be inspected for cracks in the areas surrounding the points of attachment of the generator to the cover. Prior to the inspection, the paint in these areas should be removed. The inspections should be accomplished by the dye penetrant method. Covers found with cracks should be replaced immediately. These inspections are to be accomplished at every intermediate inspection.
(b) Vibration isolators S14-35-4442 and S14-35-4443 have been designed by the manufacturer to prevent further failures. When these parts are installed in accordance with Sikorsky Information Circular No. 1435-443, the inspection outlined in item 1. (a) will be required at every major inspection for the first two inspections and then at every second major inspection if the cover has been operated without the isolator.If the cover has never been operated without the isolator, the inspection should be accomplished at the regular transmission overhaul period.
(c) The retirement time for vibration isolators is specified in Sikorsky Information Circular S14-00-354, Rev. Z.
2. (a) The upper and lower ends of the main transmission support assembly, S14-20-2503, both fore and aft, must be inspected visually for cracks at every intermediate inspection. Particular attention should be directed at the underside of the attachment points, the welded joints and the small drive screws. Assemblies found with cracks are to be replaced immediately.
(b) Prior to or at the next intermediate inspection and at every transmission overhaul thereafter, the S14-20-2503 support assemblies must be subjected to a Magnaflux inspection. Any cracks detected are cause for replacement.
3. The forward and aft lugs, to which the S14-20-2503 supports are attached, on the upper housing of the main transmissionmust be inspected at every major inspection. This inspection should be directed at each face of each lug in the area surrounding the bushing. Any crack detected is cause for replacement.
4. (a) The main rotor control servo brackets, S14-40-2113, S14-40-2143 and S14-40-2411 should be inspected for cracks in the area of the bracket ears. Prior to the inspection, all paint should be removed. The inspections should be accomplished by the dye penetrant method. Parts found with cracks should be replaced immediately. The exposed surfaces of brackets found satisfactory for return to service should be protected with several coats of zinc chromate primer. Extreme care should be taken in the installation procedure of either new or old brackets. These inspections are to be accomplished every 30 hours.
(b) The inspections of 4. (a) will no longer be necessary when steel servo brackets S14-40-2415 are installed in accordance with Sikorsky Service Information Circular No. 1440-457 dated March 24, 1954.
5. The main rotor scissors bracket assembly S10-14-1447, should be inspected for sufficient edge distance at the bolt hole through which the scissors assembly S10-10-4350, is secured. A minimum edge diameter of 5/32 inch is allowable. Any S10-10-1447 brackets with less than 5/32-inch edge distance should be replaced. These inspections are to be performed on those helicopters with the S10-10-1400 Timken rotor head and are to be accomplished every 30 hours.
(Sikorsky Service Information Circular No. 1435-383 dated September 3, 1953, as amended by revision A dated April 28, 1954, and revision B dated June 18, 1954, covers the same subject, except that section II of the Circular is amended by paragraph 1. (c).)
This supersedes AD 53-25-02.