AD 2021-19-04 Prompted By A Report Of Cracks Discovered On The M/R Scissor Link

The FAA is adopting a new airworthiness directive (AD) for Hélicoptères Guimbal Model Cabri G2 helicopters with any metal bushing installed on the main rotor (M/R) swashplate guide bellcrank.

This AD was prompted by a report of cracks discovered on the M/R scissor link during scheduled maintenance on several helicopters. This AD requires removing all metal bushings from service, visually inspecting the lug bore area and depending on the inspection results, removing certain parts from service and installing certain part-numbered plastic bushings. This AD also prohibits installing any metal bushing on any helicopter. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective October 12, 2021.

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 Hélicoptères Guimbal (HG) Model Cabri G2 helicopters, certificated in any category, with any metal bushings installed on the main rotor (M/R) swashplate guide bellcrank and without plastic bushing part number HG22-1001 or HG modification 16-009. The NPRM published in the Federal Register on July 9, 2021 (86 FR 36241). In the NPRM, the FAA proposed to require within 50 hours time-in-service or 2 months, whichever occurs first after the effective date of this AD, disconnecting the bellcrank from the swashplate guide, removing each bolt and using a certain tool, removing certain parts from service.

The NPRM also proposed to require visually inspecting the lug bore area for corrosion and cracks and depending on the inspection results, removing certain parts from service, or repairing the area using an FAA-approved method, installing certain part-numbered plastic bushings, coating the area with a compound, reinstalling certain parts, applying a specified torque, and installing cotter pins. The NPRM was prompted by EASA AD 2019-0185, dated July 30, 2019 (EASA AD 2019-0185), issued by EASA, which is the Technical Agent for the Member States of the European Union, to correct an unsafe condition for Hélicoptères Guimbal Model Cabri G2 helicopters. EASA advises that during scheduled maintenance on several helicopters, cracks were found on the M/R scissor link due to corrosion. EASA states this corrosion was caused by stress induced by the mounting of the metal bushing  inside the lug hole. EASA further states metal bushings are also installed on the M/R swashplate guide bellcrank, where similar cracking may occur. This condition, if not addressed, could result in failure of the M/R swashplate guide bellcrank and reduced control of the helicopter.

Accordingly, EASA AD 2019-0185 requires replacing any part-numbered metal bushing with plastic bushing part number (P/N) HG22-1001. EASA AD 2019-0185 also prohibits installing any part-numbered metal bushing on the M/R swashplate guide bellcrank other than P/N HG22-1001 on any helicopter.

FMI: www.regulations.gov