AD 82-20-06 R1

82-20-06 R1 BOEING AIRPLANE COMPANY, VERTOL DIVISION: Amendment 39- 4467 as revised by Telegram issued December 9, 1983, and Amendment 39-4825. Applies to Boeing Vertol Model 234 series helicopters certificated in all categories equipped with main rotor hubs, P/N's 114R2050-17, -18, -23, and -24. Compliance is required as indicated unless already accomplished.

To inspect the aft main rotor hub for cracks, within the next 60 hours time in service from the effective date of this AD or before the accumulation of 700 hours time in service, whichever comes later, and to inspect the forward main rotor hub for cracks, within the next 25 hours time in service from the effective date of this AD revision or before the accumulation of 450 hours time in service, whichever comes later, accomplish the following.

(a) Remove the hub retaining nut and washer and inspect for a height difference between the top of the shaft spline up to the rotor hub upper surface. The hub upper surfacemust be a minimum of 0.015 inches above the rotorshaft spline.

(b) Remove the rotor hubs from the aircraft and conduct an eddy current inspection for cracks on the bottom surface of the hub from the splines to a distance one inch out from the splines. Inspect the lower hub surface described above and the splined area from the lower surface upward for 1.75 inches using dye penetrant.

(c) Ensure that the washer between the main rotor shaft nut and main rotor hub is installed and torque the main rotor hub nut to the manufacturer's specifications as shown in the Boeing Vertol 234 Maintenance Manual.

(d) After the initial inspections of paragraphs (a), (b) and (c), repeat the main rotor hub inspections of paragraphs (b) and (c) in intervals not to exceed 125 hours additional time in service from the last inspection.

(e) Remove from service hubs having cracks and replace with a serviceable part prior to further flight.

(f) Boeing Vertol Service Bulletin Number 234-65-1026 applies to these inspections.

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

Amendment 39-4467 became effective October 15, 1982.

The telegraphic airworthiness revision issued on December 9, 1983, became effective upon receipt.

This Amendment 39-4825 becomes effective March 16, 1984, as to all persons except those persons to whom it was made immediately effective by telegraphic AD No. T82-20-06 R1 issued December 9, 1983, which contained the amendment.