DATE: July 6, 2021
AD #: 2021-15-51
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
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
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.
Related Service Information
The FAA reviewed the following Bell Alert Service Bulletins (ASBs), each
dated July 5, 2021:
- ASB 204B-21-74 for Bell Model 204B helicopters, S/Ns 2001 through 2070
and 2196 through 2199;
- ASB 205-21-117 for Bell Model 205A and 205A-1 helicopters, S/Ns 30001
through 30065, 30067 through 30165, 30167 through 30187, 30189 through
30296, and 30298 through 30332;
- ASB 205B-21-71 for Bell Model 205B helicopters, S/Ns30066, 30166, 30188
and 30297; and
- ASB 212-21-165 for Bell Model 212 helicopters, S/Ns 30501 through 30999,
31101 through 31311, 32101 through 32142, and 35001 through 35103.
The ASBs specify removing all P/N 204-012-104-005 pins with an S/N prefix
"FNFS" before further flight. The ASBs also specify that, although the
investigation is still in progress, removing these pins from service is
required. The ASBs state that these pins may not have been manufactured
in accordance with the engineering design requirements and may therefore
shear as a result of this nonconformance.
The FAA is issuing this emergency AD after evaluating all the relevant
information and determining that the unsafe condition described previously
is likely to exist or develop in other products of these same type designs.
This emergency AD requires removing all P/N 204-012-104-005 pins with
an S/N prefix "FNFS" before further flight. This emergency AD also prohibits
installing this pin on any helicopter as of the effective date of this
The FAA considers this emergency AD to be an interim action. If final
action is later identified, the FAA might consider further rulemaking.
Authority for this Rulemaking
Title 49 of the United States Code specifies the FAA’s authority to issue
rules on aviation safety. Subtitle I, Section 106, describes the authority
of the FAA Administrator. Subtitle VII, Aviation Programs, describes in
more detail the scope of the Agency’s authority.
The FAA is issuing this rulemaking under the authority described in Subtitle
VII, Part A, Subpart III, Section 44701, General requirements. Under that
section, Congress charges the FAA with promoting safe flight of civil
aircraft in air commerce by prescribing regulations for practices, methods,
and procedures the Administrator finds necessary for safety in air commerce.
This regulation is within the scope of that authority because it addresses
an unsafe condition that is likely to exist or develop on products identified
in this rulemaking action.
Presentation of the Actual Emergency AD
The FAA is issuing this AD under 49 U.S.C. Section 44701 according to
the authority delegated to me by the Administrator.