Korean War Era Helicopters Still Flying, Now With Cracking Parts
Published Date: 1/14/2025
Proposed Rule
Summary
If you own or work with Siam Hiller UH-12E helicopters, listen up! The FAA wants you to check the main rotor drive shafts for cracks and stop using certain paint removers to keep your choppers safe. You’ve got until February 28, 2025, to share your thoughts, and these changes could save you from costly repairs down the road.
Analyzed Economic Effects
3 provisions identified: 0 benefits, 3 costs, 0 mixed.
Mandatory drive-shaft inspections and bake
If you own or operate a Siam Hiller UH-12E or UH-12E-L with a main rotor drive shaft P/N 23600, you must inspect that drive shaft when it has 1,200 or more hours time-in-service (TIS), or is 4 or more years since new, or at the next overhaul after the AD's effective date. With the shaft removed you must strip coatings using TT-R-248B or TT-R-2918A Type I, hydrogen-embrittlement relief bake it for a minimum of 24 hours at 375°F ±25°F, and perform a magnetic particle inspection; the FAA estimates the inspection sequence costs $925 per helicopter (5 work-hours at $85/hour plus $500 parts) and affects 110 U.S. helicopters.
Installation and paint-stripper limits
As of the effective date of this AD, you may not install a main rotor drive shaft P/N 23600 on any helicopter unless the required removal, bake, and magnetic particle inspection have been completed. Also, you may not use any paint stripper other than TT-R-248B or TT-R-2918A Type I to remove coatings from the M/R drive shaft.
Certified NDT inspector required
The magnetic particle inspection of the M/R drive shaft must be done by a Level II or Level III inspector certified to FAA-acceptable nondestructive inspection standards (examples in Advisory Circular 65-31B). That means you must use qualified NDT personnel to perform the inspection required by this AD.
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