AD 2021-15-51 Prompted By A Fatal Accident In Which An Outboard Main Rotor Hub Strap Pin Sheared Off

The FAA is adopting a new airworthiness directive (AD) for certain Bell Textron Inc. (type certificate previously held by Bell Helicopter Textron Inc.) Model 204B, 205A, 205A-1, 205B, and 212 helicopters.

This AD was prompted by a fatal accident in which an outboard main rotor hub strap pin (pin) sheared off during flight, resulting in the main rotor blade and the main rotor head detaching from the helicopter. This AD requires removing the pins from service before further flight and prohibits installing them on any helicopter. The FAA previously sent an emergency AD to all known U.S. owners and operators of these helicopters and is now issuing this AD to address the unsafe condition on these products. This AD is effective August 24, 2021. Emergency AD 2021-15-51, issued on July 6, 2021, which contained the requirements of this amendment, was effective with actual notice. The FAA must receive comments on this AD by September 23, 2021.

Supplementary Information: On July 6, 2021, the FAA issued Emergency AD 2021-15-51 (Emergency AD 2021-15-51), which requires, before further flight, removing from service all part number (P/N) 204-012-104-005 pins with a serial number (S/N) prefix “FNFS”. Emergency AD 2021-15-51 also prohibits installing the pin on any helicopter as of the emergency AD's effective date. The FAA sent Emergency AD 2021-15-51 to all known U.S. owners and operators of these helicopters.

Emergency AD 2021-15-51 was prompted by a fatal accident on a Bell Textron Inc. Model 212 helicopter in which a pin P/N 204-012-104-005 with an S/N prefix “FNFS” sheared off during flight, which resulted in the main rotor blade and the main rotor head detaching from the helicopter. The pin had accumulated only 20 total hours time-in-service (TIS). An inspection of a different Model 212 helicopter revealed that another pin installed, and made by the same manufacturer and with the same S/N prefix, was deformed; this pin had accumulated only 29 total hours TIS. Failure of the pin could result in the main rotor blade detaching from the helicopter and subsequent loss of control of the helicopter.

Prior to the FAA issuing Emergency AD 2021-15-51, Transport Canada, which is the aviation authority for Canada, issued Canadian Emergency AD CF-2021-23, dated July 5, 2021 (Transport Canada Emergency AD CF-2021-23), to correct an unsafe condition for the following Bell Helicopter Textron Inc., helicopters:

• Model 204B helicopters, S/Ns 2001 through 2070 and 2196 through 2199;
• Model 205A-1 helicopters, S/Ns 30001 through 30065, 30067 through 30165, 30167 through 30187, 30189 through 30296, and 30298 through 30332;
• Model 205B helicopters, S/Ns 30066, 30166, 30188, and 30297; and
• Model 212 helicopters, S/Ns 30501 through 30999, 31101 through 31311, 32101 through 32142, and 35001 through 35103.

Transport Canada advises that during an investigation of a Bell Textron Inc., Model 212 fatal accident in Canada, it was discovered that a pin P/N 204-012-104-005 with an S/N prefix “FNFS”, sheared off during flight, leading to detachment of the main rotor blade and the main rotor head. The pin had accumulated only 20 hours of service, and inspection of another Canadian Bell Textron Inc., Model 212 helicopter found a pin of the same P/N, made by the same manufacturer, with the same S/N prefix “FNFS”, to be deformed after only approximately 29 hours in service. According to Transport Canada, failure of a main rotor hub strap pin will result in detachment of the main rotor blade and loss of control of the helicopter.

Transport Canada also advises that, although the defective pins were only reported on Bell Textron Inc., Model 212 helicopters, pins of the same P/N can also be installed on Bell Textron Inc., Model 204B, 205A-1, and 205B helicopters. While the cause of failure has not been determined, as a precautionary measure and to address the risk of detachment of main rotor hub strap pins in flight, Bell has issued Alert Service Bulletins to require replacing all pins with P/N 204-012-104-005 that have S/N prefix “FNFS”. Accordingly, Transport Canada Emergency AD CF-2021-23 mandates replacement of affected pins. Transport Canada considers its emergency AD an interim action and states that further AD action may follow.

FMI: www.regulations.gov