AD 84-03-51

84-03-51 BOEING VERTOL COMPANY: Amendment 39-4823. Applies to Boeing Vertol Model 234 series helicopters certificated in all categories.

Compliance is required as indicated.

To prevent possible hazards in flight associated with cracking of the main rotor head tie bars, accomplish the following:

(a) Unless already accomplished, within the next 25 hours time in service from the effective date of this AD or before the accumulation of 450 hours time in service, whichever comes later, and thereafter as specified in paragraphs (c) and (d) of this AD, visually inspect for cracks in the forward main rotor tie bars P/N 114R21551 with serial numbers A13207 and below. If the letter "B" is shown after the serial number, this AD does not apply.

(b) Unless already accomplished, within the next 25 hours time in service from the effective date of this AD or before the accumulation of 550 hours time in service, whichever comes later, and thereafter as specified in paragraphs (c) and (d) of this AD, visually inspect for cracks in the aft main rotor tie bars P/N 114R21551 with serial numbers A13207 and below. If the letter "B" is shown after the serial number, this AD does not apply.

(c) After the initial inspections in paragraphs (a) and (b) or the inspections in paragraph (d), repeat visual inspections of tie bars at intervals not to exceed 450 hours time in service for tie bars in paragraph (a) and 550 hours time in service for paragraph (b).

(d) Whenever a main rotor head is disassembled to inspect or replace the hub, horizontal hinge pin, or pitch shaft, conduct the inspection of tie bars specified in paragraph (a) or (b).

(e) Remove from service tie bars having a crack and replace with a serviceable part prior to further flight.

(f) An equivalent method of compliance with this AD may be used when approved by the Manager, New York Aircraft Certification Office, 181 South Franklin Avenue, Valley Stream, New York 11581.

(g) In accordance with FAR 21.197, flight is permitted to a base where the requirements of this AD may be accomplished.

This amendment becomes effective March 14, 1984, as to all persons except those persons to whom it was made immediately effective by telegraphic AD No. T84-03-51 issued January 27, 1984, which contained the amendment.