DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-1074; Project Identifier MCAI-2021-00447-R]
RIN 2120-AA64

Airworthiness Directives; Bell Textron Canada Limited Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Supplemental notice of proposed rulemaking (SNPRM).

-----------------------------------------------------------------------

SUMMARY: The FAA is revising a notice of proposed rulemaking (NPRM)
that applied to certain Bell Textron Canada Limited Model 429
helicopters. This action revises the NPRM by revising the Required
Actions paragraphs to include calendar compliance times. The FAA is
proposing this airworthiness directive (AD) to address the unsafe
condition on these products. Since these actions would impose an
additional burden over those in the NPRM, the agency is requesting
comments on this SNPRM.

DATES: The FAA must receive comments on this SNPRM by June 6, 2022.

ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:
Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow the 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 SNPRM, 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 productsupport@bellflight.com; 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)
222-5110.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-1074; or in person at
Docket Operations between 9 a.m. and 5 p.m., Monday through Friday,
except Federal holidays. The AD docket contains the NPRM, this SNPRM,
the Transport Canada AD, any comments received, and other information.
The street address for Docket Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Andrea Jimenez, Aerospace Engineer,
COS Program Management Section, Operational Safety Branch, Compliance &
Airworthiness Division, FAA, 1600 Stewart Ave., Suite 410, Westbury, NY
11590; telephone (516) 228-7330; email andrea.jimenez@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

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-2021-1074; Project Identifier
MCAI-2021-00447-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 again
revise 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 proposed AD.

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 SNPRM 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 SNPRM, 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 SNPRM.
Submissions containing CBI should be sent to Andrea Jimenez, Aerospace
Engineer, COS Program Management Section, Operational Safety Branch,
Compliance & Airworthiness Division, FAA, 1600 Stewart Ave., Suite 410,
Westbury, NY 11590; telephone (516) 228-7330; email
andrea.jimenez@faa.gov. Any commentary that the FAA receives which is
not specifically designated as CBI will be placed in the public docket
for this rulemaking.

Background

The FAA issued an NPRM to amend 14 CFR part 39 by adding an AD that
would apply to Bell Textron Canada Limited Model 429 helicopters,
serial numbers (S/N) 57001 and subsequent. The NPRM published in the
Federal Register on December 23, 2021 (86 FR 72891). In the NPRM, the
FAA proposed to require visually inspecting the external surface of the
tail rotor (TR) gearbox support assembly, borescope inspecting or
visually inspecting the inside of the tailboom for certain conditions,
and performing a tactile inspection. Depending on the results of the
inspections, the NPRM proposed to require removing certain rivets from
service or repairing gaps in accordance with FAA-approved methods. The
NPRM also proposed to require repeating these inspections within
certain intervals.
The NPRM was prompted by Transport Canada AD CF-2021-15, dated
April 14, 2021 (Transport Canada AD CF-2021-15), issued by Transport
Canada, which is the aviation authority for Canada, to correct an
unsafe condition for Bell Textron Canada Limited Model 429 helicopters,
S/N 57001 and subsequent. Transport Canada advises of multiple in-
service reports of failed rivets at the joint between the tailboom skin
and the TR gearbox support assembly part number (P/N) 429-034-701-101
or P/N 429-035-705-101. Transport Canada states that in-service reports
also revealed a quality escape resulted in a gapping condition between
the tailboom skin and the TR gearbox support fitting at some locations
around the joint, and that rivets of inadequate grip length have been
installed at the affected joint. This condition, if not addressed,
could result in progressive deterioration of the joint structural
integrity, detachment of the TR gearbox support assembly and loss of
control of the helicopter.
Accordingly, Transport Canada AD CF-2021-15 requires, for certain
serial-numbered helicopters, an initial visual inspection of the rivets
at the TR gearbox support assembly for signs of failed rivets or
inadequate grip length. Transport Canada AD CF-2021-15 also requires,
for all serial-numbered helicopters defined in the applicability,
repeating the initial visual inspection at intervals not to exceed 400
hours air time or 12 months, whichever occurs first. Transport Canada
AD CF-2021-15 also requires repair or replacement of affected parts if
discrepancies are found. Transport Canada considers its AD an interim
action and stated that further AD action may follow.

Actions Since the NPRM Was Issued

Since the NPRM was issued, the FAA determined that due to thermal
cycling the compliance times in the NPRM should be revised to include
calendar compliance times. According to Bell, thermal cycling is
independent of flight hours (FH) and can occur when an aircraft is
stationary and is also a significant contributor to the unsafe
condition. Accordingly, the FAA has determined the proposed paragraph
(g) of the proposed AD must be revised by including calendar compliance
times.
Also, since the NPRM was issued, the FAA determined the proposed
paragraph (g)(1)(iii) of the proposed AD must be revised by deleting
the word ``not'' when referring to whether or not a rivet comes out
when pulled with pliers or when pulled by hand. This wording was a
minor editorial error and the correct wording should only state
``does.''

Comments

The following discussion presents the comments received on the NPRM
and the FAA's response.

Request To Revise the Required Actions Paragraphs of the Proposed AD

Bell requested that the FAA revise the Required Actions paragraphs
of the proposed NPRM dealing with the compliance time intervals by
including the calendar compliance time. The commenter explained the
reasoning for calendar intervals is based on thermal cycling, which
could be a contributing factor to the rivets failing. The commenter
further stated thermal cycling can occur when the aircraft is
stationary.
The FAA agrees and has revised the Required Actions paragraphs in
this proposed AD to include calendar compliance times, which correspond
to the compliance times specified in Transport Canada AD CF-2021-15.
Since the calendar time is a component of the unsafe condition, the FAA
has determined there should be no differences between this proposed AD
and the Transport Canada AD in regards to the calendar compliance time.
The FAA also revised the Differences Between this SNPRM and Transport
Canada AD CF-2021-15 paragraph in this proposed AD by deleting the
paragraphs associated with the calendar interval differences.
Bell requested that the FAA revise the Required Actions paragraphs
of the proposed AD by including instructions to replace any rivet that
is removed from service. The commenter stated missing or defective
rivets without a gapping condition should be replaced in accordance
with a Bell structural repair manual; and missing or defective rivets
with excessive gapping should be repaired by contacting Bell for an
approved repair method for the gapping condition and replacement of the
rivets.
The FAA disagrees. For the excessive gapping condition, paragraph
(g)(1)(i)(B) of this proposed AD requires operators to repair the gaps
in accordance with an FAA-approved method. The FAA does not require
operators to contact Bell for approved repair methods. Where the
commenter refers to replacing rivets for certain conditions, paragraphs
(g)(1)(i)(A), (g)(1)(i)(B), (g)(1)(ii)(B), and (g)(1)(iii) of this
proposed AD only require that operators remove the rivets from service.
This proposed AD does mandate the method that operators must use to
replace removed rivets. To replace rivets, operators are expected to
use FAA-accepted methods, such as a Bell structural repair manual.
Bell requested that the FAA revise the Required Actions paragraph
of the proposed NPRM by deleting ``not'' in paragraph (g)(1)(iii) of
the proposed AD and only keeping ``does.'' The commenter stated that
this inspection is to ensure that the rivets heads are not fractured,
and if the rivet does come out when pulled with pliers or when pulled
by hand, then the rivet should be removed from service.
The FAA agrees and has revised paragraph (g)(1)(iii) of this
proposed AD by deleting ``does not'' and replacing it with ``does.''
The FAA intended to correspond with the actions specified Bell Alert
Service Bulletin (ASB) 429-19-47, Revision B, dated January 27, 2021
(ASB 429-19-47 Rev B), and misinterpreted the discrepant condition for
the tactile inspection.

FAA's Determination

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 its AD. The FAA is proposing this AD after determining the
unsafe condition described previously is likely to exist or develop in
other helicopters of the same type design. Certain changes described
above expand the scope of the NPRM. As a result, it is necessary to
reopen the comment period to provide additional opportunity for the
public to comment on this SNPRM.

Related Service Information Under 1 CFR Part 51

The FAA reviewed ASB 429-19-47 Rev B. This service information
specifies procedures for an initial and repetitive general visual
inspections and detailed inspections of the affected rivets at the
joint between the tailboom skin and the TR gearbox support assembly.
This service information also specifies procedures for replacing the
affected rivets and repairing the gaps in accordance with an approved
Bell structural repair scheme.
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 also reviewed Bell ASB 429-19-47, dated August 28, 2019
(ASB 429-19-47), and Bell ASB 429-19-47, Revision A, dated November 2,
2020 (ASB 429-19-47 Rev A). ASB 429-19-47 specifies the same general
visual inspection as ASB 429-19-47 Rev A however, ASB 429-19-47 Rev A
introduces a repetitive inspection and specifies corrective actions if
any discrepant rivets are found. ASB 429-19-47 Rev A specifies the same
procedures for the initial and repetitive general visual inspections
and detailed inspections as ASB 429-19-47 Rev B however, ASB 429-19-47
Rev B revises the compliance section, description section, and
materials section, and also the accomplishment instructions.

Proposed AD Requirements in This SNPRM

For Model 429 helicopters with S/N 57002 through 57210 inclusive
and S/N 57212 and subsequent that, as of the effective date of this
proposed AD, have accumulated less than 300 total hours time-in-service
(TIS), within 100 hours TIS or 6 months after accumulating 300 total
hours TIS, whichever occurs first; or for Model 429 helicopters with S/
N 57002 through 57210 inclusive and S/N 57212 and subsequent that, as
of the effective date of this proposed AD, have replaced certain part-
numbered TR gearbox support assemblies and the helicopter has
accumulated less than 300 total hours TIS since the replacement of the
TR gearbox support assembly, within 100 hours TIS or 6 months after
accumulating 300 total hours TIS since the replacement, whichever
occurs first, this proposed AD would require visually inspecting the
external surface of the TR gearbox support assembly for any rivet heads
that have separated from their tail, measuring any gaps, and before
further flight, removing affected rivets from service or repairing gaps
in accordance with FAA-approved methods.
This proposed AD would also require either borescope inspecting or
using a light source and mirror to visually inspect each rivet inside
the tailboom for missing rivet tails, rivet tails not resting against
the tailboom skin, and any rivet tails resting at the bottom of the
tailboom. Depending on the inspection results, this proposed AD would
require, before further flight, additional inspections or removing
certain parts from service. This proposed AD would require performing a
tactile inspection of certain rivets identified in the applicable
service information and depending on the inspection results, removing
rivets from service before further flight.
For Model 429 helicopters with S/N 57002 through 57210 inclusive
and S/N 57212 and subsequent that are not identified in paragraph
(g)(1) of this proposed AD, this proposed AD would require, within 100
hours TIS or 6 months after the effective date of this proposed AD,
whichever occurs first, performing the visual inspection of the TR
gearbox support assembly, visually inspecting or borescope inspecting
each rivet inside the tailboom, performing the tactile inspection, and
accomplishing the applicable corrective actions described previously.
For Model 429 helicopters S/N 57002 through 57210 inclusive and S/N
57212 and subsequent, this proposed AD would require, within 400 hours
TIS or 12 months, whichever occurs first after the initial inspections
required by this proposed AD, as applicable to your helicopter, and
thereafter at intervals not to exceed 400 hours TIS or 12 months,
whichever occurs first, performing the visual inspection of the TR
gearbox support assembly, visually inspecting or borescope inspecting
each rivet inside the tailboom, performing the tactile inspection, and
accomplishing the applicable corrective actions described previously.
For Model 429 helicopters S/N 57001 and 57211, this proposed AD
would require, within 400 hours TIS or 12 months after the effective
date of this proposed AD, whichever occurs first, and thereafter at
intervals not to exceed 400 hours TIS or 12 months, whichever occurs
first, performing the visual inspection of the TR gearbox support
assembly, visually inspecting or borescope inspecting each rivet inside
the tailboom, performing the tactile inspection, and accomplishing the
applicable corrective actions described previously.

Differences Between This SNPRM and Transport Canada AD CF-2021-15

Transport Canada AD CF-2021-15 requires replacing any rivets, and
repairing any gaps that exceed 0.005 in (0.127 mm), in accordance with
an approved Bell structural repair scheme, and submitting certain
information to the manufacturer, whereas this proposed AD would require
removing the rivets from service and repairing the gaps using an FAA-
approved method instead. Transport Canada AD CF-2021-15 requires
replacing any rivets if any gaps are 0.005 in (0.127mm) or less,
whereas this proposed AD would require removing the rivets from
service.

Interim Action

The FAA considers this proposed AD would be an interim action. Once
final action has been identified, the FAA might consider further
rulemaking.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 120 helicopters of U.S. Registry. Labor rates are estimated at
$85 per work-hour. Based on these numbers, the FAA estimates the
following costs to comply with this proposed AD.
Visually inspecting the surface of the TR gearbox support assembly
would take about 0.5 work-hour for an estimated cost of $43 per
inspection and $5,160 for the U.S. fleet per inspection.
If required, replacing any affected rivets would take about 1 work-
hour and parts would cost about $110 per rivet for an estimated cost of
$195 per rivet replacement.
If required, measuring gaps would take about 0.5 work-hour for an
estimated cost of $43 per helicopter.
If required, repairing any gaps would take up to about 1 work-hour
for an estimated cost of up to $85 per repair.

Visually inspecting or borescope inspecting the inside of the
tailboom would take about 0.5 work-hour for an estimated cost of $43
per inspection and $5,160 for the U.S. fleet per inspection.
Performing a tactile inspection would take about 0.5 work-hour for
an estimated cost of $43 per inspection and $5,160 for the U.S. fleet
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.

Regulatory Findings

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
Order 12866,
(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
reference, Safety.

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
directive: