During the first full week of July, Transport Canada and the FAA issued emergency airworthiness directives (ADs) requiring operators of Bell Model 212 and other helicopters to immediately inspect their main-rotor hubs for potentially faulty hub strap pins.

The aviation regulatory authorities issued the directives following the June 28 crash of a Yellowhead Helicopters Bell 212 during firefighting operations near the town of Evansburg, in Alberta, Canada, west of Edmonton. The crash killed the pilot, the helicopter’s only occupant.

Investigators discovered that an outboard main-rotor hub strap pin with part number (P/N) 204-012-104-005 and the serial number prefix FNFS had sheared off during flight, which resulted in the main rotor blade and main rotor head detaching from the helicopter. The pin had accumulated just 20 total hours of time in service.

Although defective strap pins were found only on the accident helicopter and another Bell 212 examined by Canadian investigators, strap pins of the same P/N can also be installed on Bell 204B, 205A-1 and 205B models—civilian variants of the UH-1 Iroquois (Huey) military helicopter.

The FAA estimates the emergency directives affect 140 standard-category helicopters in the U.S. and 400 worldwide. They affect an estimated 359 restricted-category helicopters registered in the U.S. and 529 worldwide. Restricted category helicopters are primarily used by the military, law enforcement agencies, and forest and wildlife services as well as for mineral exploration and other purposes

Emergency Airworthiness Directives
The aviation authorities issued the following emergency ADs:

• Transport Canada CF-2021-23, issued July 5
• FAA AD 2021-15-51, issued July 6
• FAA AD 2021-15-52, issued July 8

Manufacturer’s Service Bulletins
Bell Textron issued Alert Service Bulletins (ASB) dated July 5, specifying main rotor hub inspections and removing strap pins if necessary on certain Model 212 (ASB 212-21-165); 204B (ASB 204B-21-74); and 205A/A-1 (ASB 205-21-117) helicopters before further flight.

Bell posted three ASBs on July 7 covering derivative models, listed below. The manufacturer estimates that about 20 hours would be needed to replace affected pins, and that four pins may be needed.

• ASB 210-21-14: Affects all Model 210 helicopters (refurbished UH-1H Huey fuselage with Bell 212 components)
• ASB UH-1H-21-21: Affects all UH-1H Hueys
• ASB UH-1H-II-21-31: Affects all Model UH-1H-IIs (upgraded UH-1Hs)

Additional Helicopter Variants
After issuing its July 6 directive, the FAA determined that hub strap P/N 204-012-104-005 with the serial number prefix FNFS could also be installed on restricted-category helicopters originally manufactured by Bell Textron. FAA AD 2021-15-52 expands the inspection and replacement requirement to the following models:

• Rotorcraft Development Corp. Model HH-1K 

• Robinson Air Crane; Rotorcraft Development Corp.; and Tamarack 
Helicopters Model TH-1F

• Bell Textron Overseas Aircraft Support, Inc. (a type certificate previously held by JTBAM); and Rotorcraft Development Corporation Model TH-1L 
• Richards Heavylift Helo, Model UH-1A 
International Helicopters; Overseas Aircraft Support; Red Tail Flying Services; Richards Heavylift Helo; Rotorcraft Development Corp.; Southwest Florida Aviation International; and WSH, LLC (a type certificate previously held by San Joaquin Helicopters), Model UH-1B 

• Bell Textron; Overseas Aircraft Support; Rotorcraft Development Corp.; Smith Helicopters; and West Coast Fabrications Model UH-1E 
• AST; California Department of Forestry; Robinson Air Crane; Rotorcraft Development Corp.; and Tamarack Helicopters Model UH-1F 
• Arrow Falcon Exporters; Global Helicopter Technology; Hagglund Helicopters; JJASPP Engineering Services; Northwest Rotorcraft; Overseas Aircraft Support; Richards Heavylift Helo; Rotorcraft Development Corp.; Southwest Florida Aviation International; and Tamarack Helicopters Model UH-1H 
• Bell Textron; Overseas Aircraft Support; and Rotorcraft Development Corp. Model UH-1L; and 
• Robinson Air Crane and Rotorcraft Development Corp. Model UH-1P