DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2021-0728; Project Identifier MCAI-2020-00656-R]
Airworthiness Directives; Bell Textron Canada Limited
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed rulemaking (NPRM).
SUMMARY: The FAA proposes to adopt a new airworthiness directive
for certain Bell Textron Canada Limited Model 206, 206A, 206A-1, 206B,
206B-1, 206L, 206L-1, 206L-3, and 206L-4 helicopters. This proposed AD
was prompted by reports of cracked or missing nuts on the tail rotor drive
shaft (TRDS) disc pack (Thomas) couplings. This proposed AD would
require removing certain nuts from service, installing newly designed
nuts, and applying a specific torque and a torque stripe to each newly
installed nut. This proposed AD would then require, after the
installation of each newly designed nut, inspecting the torque and,
depending on the inspection results, either applying a torque stripe or
performing further inspections and removing certain parts from service.
Finally, this proposed AD would prohibit installing any affected nut on
any TRDS Thomas coupling.
The FAA is proposing this AD to address the unsafe condition on
DATES: The FAA must receive comments on this proposed AD by October
ADDRESSES: You may send comments, using the procedures found in
11.43 and 11.45, by any of the following methods:
Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow
instructions for submitting comments.
Fax: (202) 493-2251.
Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.
Hand Delivery: Deliver to Mail address between 9 a.m. and
5 p.m., Monday through Friday, except Federal holidays.
For service information identified in this NPRM, contact Bell
Textron Canada Limited, 12,800 Rue de l'Avenir, Mirabel, Quebec J7J
1R4, Canada; telephone 1-450-437-2862 or 1-800-363-8023; fax 1-450-433-
0272; email firstname.lastname@example.org; or at https://www.bellflight.
com/support/contact-support. You may view this service
information at the FAA, Office of the Regional Counsel, Southwest
Region, 10101 Hillwood Pkwy., Room 6N-321, Fort Worth, TX 76177. For
information on the availability of this material at the FAA, call (817)
Examining the AD Docket
You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0728; or in person at
Docket Operations between 9 a.m. and 5 p.m., Monday through Friday,
except Federal holidays. The AD docket contains this NPRM, the
Transport Canada AD, any comments received, and other information. The
street address for Docket Operations is listed above.
FOR FURTHER INFORMATION CONTACT: Matt Fuller, AD Program Manager,
General Aviation & Rotorcraft Unit, Airworthiness Products Section,
Operational Safety Branch, FAA, 10101 Hillwood Pkwy., Fort Worth, TX
76177; telephone (817) 222-5110; email email@example.com.
The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under ADDRESSES. Include "Docket No. FAA-2021-0728; Project Identifier
MCAI-2020-00656-R" at the beginning of your comments. The most helpful
comments reference a specific portion of the proposal, explain the
reason for any recommended change, and include supporting data. The FAA
will consider all comments received by the closing date and may amend
this proposal because of those comments.
Except for Confidential Business Information (CBI) as described in
the following paragraph, and other information as described in 14 CFR
11.35, the FAA will post all comments received, without change, to
https://www.regulations.gov, including any personal information you
provide. The agency will also post a report summarizing each
substantive verbal contact received about this NPRM.
Confidential Business Information
CBI is commercial or financial information that is both customarily
and actually treated as private by its owner. Under the Freedom of
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public
disclosure. If your comments responsive to this NPRM contain commercial
or financial information that is customarily treated as private, that
you actually treat as private, and that is relevant or responsive to
this NPRM, it is important that you clearly designate the submitted
comments as CBI. Please mark each page of your submission containing
CBI as "PROPIN." The FAA will treat such marked submissions as
confidential under the FOIA, and they will not be placed in the public
docket of this NPRM. Submissions containing CBI should be sent to Matt
Fuller, AD Program Manager, General Aviation & Rotorcraft Unit,
Airworthiness Products Section, Operational Safety Branch, FAA, 10101
Hillwood Pkwy., Fort Worth, TX 76177; telephone (817) 222-5110; email
firstname.lastname@example.org. Any commentary that the FAA receives which is
not specifically designated as CBI will be placed in the public docket
for this rulemaking.
Transport Canada, which is the aviation authority for Canada, has
issued Canadian AD CF-2019-34, dated September 25, 2019 (Transport
Canada AD CF-2019-34), to correct an unsafe condition for Bell
Helicopter Textron Canada Limited (now Bell Textron Canada Limited)
Model 206, 206A, 206A-1, 206B, 206B-1, 206L, 206L-1, 206L-3, and 206L-4
helicopters, all serial numbers. Transport Canada AD CF-2019-34 advised
of reports of cracked or missing nuts at the TRDS Thomas couplings,
which could have been caused by improper torque or hydrogen
embrittlement. This condition, if not addressed, could result in loss
of the tail rotor and subsequent loss of control of the helicopter.
After Transport Canada issued Transport Canada AD CF-2019-34, it
was determined that helicopters modified in accordance with
Supplemental Type Certificate (STC) SH2750NM or Transport Canada STC
SH99-202, were not able to comply with AD CF-2019-34. Accordingly,
Transport Canada issued AD CF-2020-15, dated May 13, 2020 (Transport
Canada AD CF-2020-15) which supersedes Transport Canada AD CF-2019-34,
and contains a new requirement for helicopters with STC SH2750NM or
Transport Canada STC SH99-202 installed or models that have been
modified per Bell Service Instruction BHT-206-SI-2052, Revision 1,
dated October 14, 2010 (BHT-206-SI-2052). Transport Canada advises for
certain model helicopters, the newly designed nuts cannot be installed
because STC SH2750NM and Transport Canada STC SH99-202 install a pulley
at the Thomas coupling location causing insufficient clearance.
Transport Canada further advises for certain model helicopters with STC
SH2750NM or Transport Canada STC SH99-202 installed, different part-
numbered nuts may be installed which were not identified in the
applicable service information and are now required to be replaced with
a new part-numbered nut that is not vulnerable to the unsafe condition.
Accordingly, Air Comm Corporation, the STC holder for STC SH2750NM,
issued new service information to address these additional issues and
provide newly developed instructions which apply to certain model
helicopters with STC SH2750NM or Transport Canada STC SH99-202
Additionally, Transport Canada advises that BHT-206-SI-2052 which
is optional, specifies procedures for Model 206L-1 and 206L-3
helicopters to upgrade the airframe and systems and also includes
installation of the Model 206L-4 TRDS Thomas coupling. According to
Transport Canada, models that have incorporated BHT-206-SI-2052, with
STC SH2750NM or Transport Canada STC SH99-202 installed, will have the
Model 206L-4 helicopter pulley configuration and are subject to the Air
Comm Corporation service information.
Accordingly, Transport Canada AD CF-2020-15 requires the
replacement of the affected nuts with the newly designed nuts at each
TRDS Thomas coupling.
These helicopters have been approved by the aviation authority of
Canada and are approved for operation in the United States. Pursuant to
the FAA's bilateral agreement with Canada, Transport Canada, its
technical representative, has notified the FAA of the unsafe condition
described in the Transport Canada AD. The FAA is proposing this AD
after evaluating all known relevant information and determining that an
unsafe condition is likely to exist or develop on other helicopters of
the same type design.
Related Service Information Under 1 CFR Part 51
The FAA reviewed Bell Alert Service Bulletin 206-19-136, dated
August 27, 2019, and Bell Alert Service Bulletin 206L-19-181, Revision
A, dated August 29, 2019. This service information specifies procedures
for replacing the affected nuts with the newly designed corrosion-
This service information is reasonably available because the
interested parties have access to it through their normal course of
business or by the means identified in the ADDRESSES section.
Other Related Service Information
The FAA reviewed Air Comm Corporation Service Bulletin SB 206EC-
092619, Revision NC, dated September 26, 2019, which also specifies
procedures for replacing the affected nuts with the newly designed
corrosion-resistant nuts, but explains that affected helicopters
equipped with Air Comm Corporation air conditioning systems installed
under STC SH2750NM use the affected nut to attach a pulley onto the
TRDS, which causes clearance issues for the nuts to be installed at the
coupling. Therefore, this service bulletin specifies replacing the nut
with a lower profile nut.
The FAA also reviewed BHT-206-SI-2052. This service information
specifies procedures to upgrade Model 206L-1 and 206L-3 helicopters to
allow operations at an increased internal gross weight.
Proposed AD Requirements in This NPRM
This proposed AD would require within 600 hours time-in-service
(TIS) after the effective date of this AD, removing from service each
affected nut, and installing a newly designed nut. This proposed AD
would also require applying a specific torque and a torque stripe to
each newly installed nut. This proposed AD would also require, within
25 hours TIS after installation of each newly designed nut, inspecting
the torque of each nut, and depending on the results of the inspection,
this proposed AD would require further inspections and removing certain
parts from service. Finally, this proposed AD would prohibit installing
any affected nut on any on any TRDS Thomas coupling.
Differences Between This Proposed AD and the Transport Canada AD
The Transport Canada AD requires compliance within 600 hours air
time or within the next 24-months, whichever occurs first, whereas this
proposed AD would require compliance within 600 hours TIS and an
additional inspection at 25 hours TIS after installation of certain
Costs of Compliance
The FAA estimates that this proposed AD would affect 1439
helicopters of U.S. Registry. The FAA estimates that operators may
incur the following costs in order to comply with this proposed AD.
Labor costs are estimated at $85 per work-hour.
Replacing each affected nut with the newly designed nut and
applying torque and a torque stripe would take about 4 work-hours, and
parts would cost about $75 for an estimated cost of $415 per nut
replacement and $597,185 per nut replacement for the U.S. fleet.
Replacing each TRDS Thomas coupling would take about 4 work-hours,
and parts would cost about $4,000 for an estimated cost of $4,340 per
TRDS Thomas coupling replacement.
If required, inspecting the torque of each newly installed nut, and
inspecting each TRDS Thomas coupling, each bolt, nut and washer for
elongated holes and fretting on the fasteners would take about 0.5
work-hours for an estimated cost of $43 per inspection.
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.
The FAA determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would not
have a substantial direct effect on the States, on the relationship
between the national Government and the States, or on the distribution
of power and responsibilities among the various levels of government.
For the reasons discussed, I certify this proposed regulation:
(1) Is not a "significant regulatory action" under Executive
(2) Would not affect intrastate aviation in Alaska, and
(3) Would not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by
The Proposed Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 14 CFR part 39 as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. The FAA amends Sec. 39.13 by adding the following new airworthiness