AD 86-23-51

86-23-51 BOEING VERTOL: Amendment 39-5659. Applies to Boeing Vertol Model 234 series helicopters certificated in any category, equipped with forward rotor transmission P/N's 234D1200-2, -3, -4, -5, and -6 and/or aft rotor transmission P/N's 234D2200-3, -4, and -5.

Compliance is required as indicated, unless already accomplished.

To prevent failure of the spiral bevel ring gear/sun gear bolted joint, accomplish the following before further flight.

(a) For both forward and aft transmissions, remove all spiral bevel ring gears, P/N's 114D1244-5 and -6 and 114D2254-5 and -6; first stage sun gears, P/N's 234D1243-1 and -2 and 234D2250-1 and -2; and spacer shim, P/N's 114D2257-1 and -2, with more than zero hours time in service. Spiral bevel ring gears, P/N's 114D1244-6 and 114D2254-6; first stage sun gears, P/N's 234D1243-2 and 234D2250-2; and spacer shim, P/N 114D2257-2, are not eligible for further service.

(b) Install the following parts, which must be new, except for the first stage sun gear, (item (b)(2) below), which must be serviceable:

(1) Spiral bevel ring gear, P/N 114D1244-5 or 114D2254-5;

(2) First stage sun gear, P/N 234D1243-1 or 234D2250-1;

(3) Spacer shim, P/N 114D2257-1; and

(4) Associated hardware as follows:

(i) Bolt, P/N BACB30MT6T12;

(ii) Washer, P/N BACW10BP6P; and

(iii) Nut, P/N BACN10TW6.

(c) An alternate method of compliance which provides an equivalent level of safety with this AD may be used when approved by the Manager, New York Aircraft Certification Office, 181 South Franklin Avenue, Rm. 202, Valley Stream, NY 11581.

This amendment, 39-5659, becomes effective July 20, 1987, as to all persons except those persons to whom it was made immediately effective by individual telegrams issued November 14, 1986, which contained this amendment.