75-07-01 BELL: Amendment 39-2131. Applies to Bell Model 212 helicopters, S/N 30501 through S/N 30658 and 30671, certificated in all categories.
Compliance required as indicated, unless already accomplished.
Within the next 25 hours' time in service after the effective date of this AD, or before next flight if an unusual high frequency vibration is detected.
a. Gain access to and remove the main drive shaft assembly in accordance with Section 65-30-01 of the Model 212 helicopter maintenance manual.
b. Inspect the exposed nut, P/N 212-040-631-1, for serial number. Nuts with the following serial numbers are improperly manufactured and must be removed from service:
A20-00427, A20-00469, A20-00472, A20-00475, A20-00476, A20-00477, A20-00478
Nuts which have no serial number and nuts with serial numbers other than those listed are acceptable.
c. Reinstall the drive shaft with an acceptable nut in accordance with instructions in Section 65-30-01 of the Model212 maintenance manual. Notify Bell Helicopter Company or the Chief, Engineering and Manufacturing Branch, Flight Standards Division, Southwest Region, Federal Aviation Administration, if nuts identified in paragraph b. are found following inspection.
(Reporting approved by the Office of Management and Budget under OMB No. 04- R0174).
d. Bell Service Bulletin No. 212-75-1 dated February 19, 1975, pertains to this inspection and replacement procedure.
e. Equivalent methods of compliance with this airworthiness directive must be approved by the Chief, Engineering and Manufacturing Branch, Flight Standards Division, Southwest Region, Federal Aviation Administration, 4400 Blue Mound Road, Fort Worth, Texas 76101.
This amendment becomes effective April 21, 1975.