AD 2022-20-14 Prompted By Reports Of Cracks Found On The Main Transmission Support Case

The FAA is adopting a new airworthiness directive (AD) for Bell Textron Inc., Model 204B, 205A, 205A-1, 205B, 210, 212, 412, 412CF, and 412EP helicopters and various restricted category helicopters.

This AD was prompted by reports of cracks found on the main transmission support case. This AD requires repetitive inspections of the main transmission housing assembly for cracks, pitting, and corrosion and depending on the results, corrective action. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective December 27, 2022.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to Bell Textron Inc., Model 204B, 205A, 205A-1, 205B, 210, 212, 412, 412CF, and 412EP helicopters and restricted category Model HH-1K, SW205A-1, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, and UH-1P helicopters.

The NPRM published in the Federal Register on April 14, 2022 (87 FR 22146). The NPRM was prompted by reports of main transmission support cases found cracked at one of the lateral mounts. In the NPRM, the FAA proposed to require, within 3,000 hours time-in-service (TIS) accumulated by the main transmission after the effective date of the AD, and thereafter at intervals not to exceed 3,000 hours TIS accumulated by the main transmission, removing certain screws and washers and visually inspecting the upper and lower transmission support case lateral mount screws for corrosion and thread damage, washers for corrosion and pitting, bushings for corrosion and pitting, and lateral mount surfaces for corrosion and mechanical damage such as any crack or pitting. If there is any corrosion, thread damage, or mechanical damage, the NPRM proposed to require removing the affected parts from service before further flight.

The NPRM also proposed to require repetitive fluorescent penetrant inspections (FPIs) of all surfaces of the main transmission support case lateral mounts for a crack. For helicopters with a main transmission that has accumulated 6,000 or more total hours TIS, the initial FPI would be required before further flight after the effective date of the AD. For helicopters with a main transmission that has accumulated less than 6,000 total hours TIS, the initial FPI would be required before the main transmission accumulates 6,000 total hours TIS. For all helicopters, following the initial FPI, the NPRM proposed to require performing an FPI at intervals not to exceed 6,000 hours TIS accumulated by the main transmission. If there is any crack, the NPRM proposed to require removing the main transmission support case from service before further flight. The FAA is issuing this AD to address the unsafe condition on these products.

FMI: www.regulations.gov