Emergency AD Was Prompted By A Bell Model 212 Helicopter Fatal Accident

Emergency Airworthiness Directive (AD) 2021-15-51 is sent to owners and operators of Bell Textron Inc. (type certificate previously held by Bell Helicopter Textron Inc.) (Bell) Model 204B, 205A, 205A-1, 205B, and 212 helicopters.

This emergency AD was prompted by a Bell Model 212 helicopter fatal accident in which an outboard main rotor hub strap pin (pin), part number (P/N) 204-012-104-005 with a serial number (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 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.

Transport Canada, which is the aviation authority for Canada, has issued Canadian Emergency AD CF-2021-23, dated July 5, 2021 (Emergency AD CF-2021-23), to correct an unsafe condition for the following Bell 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 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 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 Model 212 helicopters, pins of the same P/N can also be installed on Bell 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, 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