73-07-05 McKINNON: Amdt. 39-1614. Applies to Model G-21 Series 73-07-05 McKinn Airplanes.
Compliance required as indicated.
Applicable to torque tube assemblies, Gruman Part Numbers 12755-1, 12756-1, 12757-1, and 12758-1, and the support tubes, Part Numbers 12725-1 and -2.
A. Applicable to those torque tube and support tube assemblies having less than 6000 hours' time in service, or less than 7 years' life since re-manufacture:
To prevent hazards in flight associated with the failure of the elevator or rudder torque tubes, unless already accomplished within the last eleven (11) months, visually inspect the external condition of the tubes within one (1) month after the effective date of this AD, and at intervals thereafter not to exceed twelve (12) months from last inspection. Tubes which are cracked or show evidence of corrosion must either be repaired or replaced in accordance with FAR Part 43 and Advisory Circular 43.13-1 prior to further flight.
B. Applicable to those torque tube and support tube assemblies having more than 6000 hours' time in service, or more than 7 years since re-manufacture. Within the next year, unless already accomplished:
(1) Visually inspect the support tubes, Part Numbers 12725-1 and -2 for corrosion. If corrosion is found, repair or replace in accordance with FAR Part 43 and Advisory Circular 43.13-1 before further flight.
(2) Remove all bolted bellcranks, arms, and pedals from the torque tubes. Using visual and dye penetrant methods, or an FAA-approved equivalent inspection, inspect the parts removed from the torque tubes for corrosion and cracking. Repair and replace in accordance with FAR Part 43 and AC 43.13-1.
(3) Discard elevator torque tube, Part Number 12755-1; rudder torque tube, Part Number 12756-1 and the L.H. and R.H. rudder pedal torque tubes, Part Numbers 12757-1 and 12758-1. Install new manufactured parts or fabricate replacement tubes in accordance with FAR 43 and AC 43.13-1 from new manufacture stock 2024-T3 (material specifications WW-T-700/3 or equivalent) in conformance with the above drawings taking special care to corrosion-proof the interior as well as the exterior surfaces of the tubes.
(4) Re-assemble and re-initiate the visual inspection program per (A) until reaching the rebuild threshold per (B).
C. Aircraft with badly corroded but uncracked torque tubes may be flown in accordance with FAR 21.197 to a base where a repair or replacement can be performed.
D. Upon submission of substantiating data by an owner or operator through an FAA Maintenance Inspector, the Chief, Engineering and Manufacturing Branch, FAA Northwest Region, may adjust the repetitive inspection intervals specified in this AD.
This supersedes Amendment 39-1525 (31 F.R. 13697), AD 72-20-04.
This Amendment becomes effective on publication.