AD 86-25-05

86-25-05 SIKORSKY AIRCRAFT: Amendment 39-5471. Applies to Model S-58A, B, C, D, E, F, G, H, J, BT, DT, ET, FT, HT, and JT, CH-34 series, HH-34 series, SH-34 series, UH- 34 series, and VH-34 series helicopters certificated in any category and fitted with tail rotor intermediate gearbox input bevel pinions Part Number (P/N) S1635-64114-0 and output bevel gears P/N S1635-64115-0. (See Note 1 for exempt pinion and gear configurations.)

Compliance is required as indicated, unless already accomplished.

(a) To preclude failure of pinions or gears identified above, accomplish the following:

(1) For applicable pinions or gears that have attained 750 or less hours' time in service on the effective date of this AD, replace with a serviceable pinion or gear as required, prior to their accumulation of 1,000 hours' time in service.

(2) For pinions or gears that have attained more than 750 hours' time in service on the effective date of this AD, replace with a serviceablepinion or gear as required, within the next 250 hours' time in service.

(3) Operators who have not kept records of hours' time in service on individual intermediate gearbox bevel gears and bevel pinions shall substitute rotorcraft hours' time in service in lieu thereof.

NOTE 1. This AD is not applicable to helicopters fitted with tail rotor intermediate gears which utilize the following pinion and gear combinations:

(a) P/N 1635-64114-101 pinion and P/N S1635-64115-101 gear. (b) P/N 1635-64114-102 pinion and P/N S1635-64115-102 gear. (c) P/N 1635-64114-0 pinion and P/N S1635-64115-0 gear reworked in accordance with Sikorsky Service Bulletin 58B35-26. This rework includes remarking P/N S1635-64114-0 pinion and P/N S1635-64115-0 gear with TS-200-1 and TS-200-2, respectively.

NOTE 2. Refer to the Equalized Inspection and Maintenance Program Manual SA 4047-20, Revision 10, dated December 14, 1984, or later FAA-approved revision for retirement times assigned tonew or modified bevel pinions and bevel gears for the Model S-58BT, DT, ET, FT, HT, and JT helicopters, and to the Maintenance Manual SA 4045-15 Section IV, revised December 14, 1984, or later FAA-approved revision for retirement times assigned to new or modified bevel pinions and gears for the Model S-58A, B, C, D, E, F, G, H, and J helicopters.

Upon request, an alternate method of compliance which provides an equivalent level of safety may be approved by the Manager, Boston Aircraft Certification Office, ANE-150, FAA, 12 New England Executive Park, Burlington, Massachusetts 01803.

Upon submission of substantiating data by an owner or operator through an FAA maintenance inspector, the Manager, Boston Aircraft Certification Office, ANE-150, FAA, 12 New England Executive Park, Burlington, Massachusetts 01803 may adjust the compliance time specified in this AD.

This amendment becomes effective on January 5, 1987.