(a) EFFECTIVE DATE
This airworthiness directive (AD) is effective November 8, 2024.
(b) AFFECTED ADS
None.
(c) APPLICABILITY
This AD applies to the Bell Textron Inc. helicopters, certificated in
any category, that are identified in paragraphs (c)(1) through (5) of
this AD.
(1) Model 212 helicopters, serial numbers (S/N) 30501 through 30603 inclu-
sive, 30611 through 30753 inclusive, 30755 through 30889 inclusive,
30891 through 30999 inclusive, 31101 through 31162 inclusive, 31164
through 31311 inclusive, 32101 through 32142 inclusive, and 35001
through 35103 inclusive;
(2) Model 412CF helicopters, S/N 46400 through 46499 inclusive;
(3) Model 412 and 412EP helicopters, S/N 33001 to 33078 inclusive, 33080
through 33129 inclusive, 33131 through 33138 inclusive, 33150 through
33213 inclusive, 36001 through 36687 inclusive, 36689 through 36999
inclusive, 37002 through 37018 inclusive, 37021 through 37051
inclusive, 38001, and 39101 through 39103 inclusive;
(4) Model 412EP helicopter, S/N 37052; and
(5) Model 412 and 412EP helicopters, S/N 36688, 37019, 37020, 37053
through 37999 inclusive, 38002 through 38999 inclusive, and 39104
through 39999 inclusive.
(d) SUBJECT
Joint Aircraft System Component (JASC) Code: 5302, Rotorcraft Tail
Boom.
(e) UNSAFE CONDITION
This AD was prompted by reports of cracked tail boom attachment barrel
nuts (barrel nuts). The FAA is issuing this AD to address fatigue
cracking of barrel nuts, damage to the tail boom attachment bolts
(bolts), and certain bolts remaining in service beyond fatigue limits.
The unsafe condition, if not addressed, could result in increased
fatigue loading and subsequent failure of the bolts, which could lead
to separation of the tail boom from the helicopter and subsequent loss
of control of the helicopter.
(f) COMPLIANCE
Comply with this AD within the compliance times specified, unless
already done.
(g) REQUIRED ACTIONS
(1) Within 300 hours time-in-service (TIS) or 90 days after the effective
date of this AD, whichever occurs first, accomplish the actions
required by paragraphs (g)(1)(i) through (iv) of this AD, as
applicable. For purposes of this AD, the word "new" is defined as
having zero total hours TIS.
(i) For all helicopters identified in paragraphs (c)(1) and (2) of this
AD; and for helicopters identified in paragraph (c)(3) of this AD that
have accumulated 5,000 or more total hours TIS or 5 or more years
since new, or if the total hours TIS or age of the helicopter is
unknown, remove the upper left-hand (LH) steel alloy barrel nut part
number (P/N) NAS577B9A and upper LH bolt from service and replace them
with a new nickel alloy barrel nut P/N NAS577C9A, new retainer P/N
NAS578C9A, and a new bolt in accordance with the Accomplishment
Instructions, part I, paragraphs 4 through 7, of Bell Alert Service
Bulletin 212-21-166, Revision A, dated February 23, 2022 (ASB 212-21
-166 Rev A), Bell Alert Service Bulletin 412CF-21-72, Revision A,
dated February 23, 2022 (ASB 412CF-21-72 Rev A), or Bell Alert Service
Bulletin 412-21-187, Revision A, dated February 23, 2022 (ASB 412-21
-187 Rev A), as applicable to your helicopter model, except you are
not required to discard parts.
(ii) For helicopters identified in paragraph (c)(3) of this AD that have
accumulated less than 5,000 total hours TIS and less than 5 years
since new, remove the upper LH steel alloy barrel nut P/N NAS577B9A,
the upper LH bolt, countersunk washer, and plain washers, and
visually inspect the removed upper LH steel alloy barrel nut for
cracking. If there is any cracking in the upper LH steel alloy barrel
nut, before further flight, remove the upper LH bolt from service. If
the upper LH bolt was not removed from service as a result of the
upper LH steel alloy barrel nut inspection, visually inspect the
upper LH bolt for any corrosion, damaged threads, wear, and fatigue
cracking. If the upper LH bolt has any corrosion, a damaged thread,
wear, or fatigue cracking, before further flight, remove the upper LH
bolt from service. Regardless of the result of the upper LH steel
alloy barrel nut inspection, remove the upper LH steel alloy barrel
nut from service and replace it with a new nickel alloy barrel nut
P/N NAS577C9A and new retainer P/N NAS578C9A. Install a new upper LH
bolt or reinstall the existing upper LH bolt, as applicable, by
following the Accomplishment Instructions, part I, paragraphs 6 and
7, of ASB 412-21-187 Rev A.
(iii) For helicopters identified in paragraphs (c)(1) through (3) of this
AD, remove the upper right-hand (RH) steel alloy barrel nut P/N
NAS577B8A, the upper RH bolt, countersunk washer, and plain washers,
and visually inspect the removed upper RH steel alloy barrel nut for
cracking. If there is any cracking in the upper RH steel alloy
barrel nut, before further flight, remove the upper RH bolt from
service. If the upper RH bolt was not removed from service as a
result of the upper RH steel alloy barrel nut inspection, visually
inspect the upper RH bolt for any corrosion, damaged threads, wear,
and fatigue cracking. If the upper RH bolt has any corrosion, a
damaged thread, wear, or fatigue cracking, before further flight,
remove the upper RH bolt from service. Regardless of the result of
the upper RH steel alloy barrel nut inspection, remove the upper RH
steel alloy barrel nut from service and replace it with a new nickel
alloy barrel nut P/N NAS577C8A and new retainer P/N NAS578C8A.
Install a new upper RH bolt or reinstall the existing upper RH bolt,
as applicable, by following the Accomplishment Instructions, part I,
paragraphs 11 and 12, of ASB 212-21-166 Rev A, ASB 412-21-187 Rev A,
or ASB 412CF-21-72 Rev A, as applicable to your helicopter model.
(iv) For helicopters identified in paragraphs (c)(1) through (3) of this
AD, remove one of the lower steel alloy barrel nuts P/N NAS577B6A,
its lower bolt, countersunk washer, and plain washers, and visually
inspect the removed lower steel alloy barrel nut for cracking. If
there is any cracking in the lower steel alloy barrel nut, before
further flight, remove the lower bolt from service. If the lower bolt
was not removed from service as a result of the lower steel alloy
barrel nut inspection, visually inspect the lower bolt for any
corrosion, damaged threads, wear, and fatigue cracking. If the lower
bolt has any corrosion, a damaged thread, wear, or fatigue cracking,
before further flight, remove the lower bolt from service. Regardless
of the result of the lower steel alloy barrel nut inspection, remove
the lower steel alloy barrel nut from service and replace it with a
new nickel alloy barrel nut P/N NAS577C6A and new retainer P/N
NAS578C6A. Install a new lower bolt or reinstall the existing lower
bolt, as applicable, by following the Accomplishment Instructions,
part I, paragraphs 16 and 17, of ASB 212-21-166 Rev A, ASB 412-21-187
Rev A, or ASB 412CF-21-72 Rev A, as applicable to your helicopter
model. Repeat the actions required by this paragraph for the other
lower tail boom attachment point.
(2) For helicopters identified in paragraphs (c)(1) through (3) of this
AD, after accumulating 1 hour TIS, but not to exceed 5 hours TIS after
accomplishing the actions required by paragraph (g)(1) of this AD,
using the torque value information in the Accomplishment Instructions,
part II, paragraph 1, of ASB 212-21-166 Rev A, ASB 412-21-187 Rev A,
or ASB 412CF-21-72 Rev A, as applicable to your helicopter model,
inspect the torque applied on each bolt. Thereafter, repeat the torque
inspection of each bolt after accumulating 1 hour TIS, but not to
exceed 5 hours TIS, to determine if the torque has stabilized. Do not
exceed three torque inspections total for each bolt and accomplish the
actions required by paragraphs (g)(2)(i) and (ii) of this AD.
Note 1 to the introductory text of paragraph (g)(2): This note applies to
the introductory text of paragraph (g)(2), the introductory text of
paragraph (g)(2)(i), paragraph (g)(2)(i)(B), and paragraph (g)(2)(ii) of
this AD. The Accomplishment Instructions, part II, paragraph 1, of ASB
212-21-166 Rev A, ASB 412-21-187 Rev A, and ASB 412CF-21-72 Rev A each
refer to part I for allowable torque limits; part I of ASB 212-21-166 Rev
A, ASB 412-21-187 Rev A, and ASB 412CF-21-72 Rev A specify the different
torque limits for the different bolts.
(i) If the torque on a bolt is below the minimum allowable torque limit as
a result of any instance of the torque inspection or if after three
torque inspection attempts, the torque on any bolt has not stabilized,
before further flight, accomplish the actions required by paragraphs
(g)(2)(i)(A) and (B) of this AD.
(A) Remove the hardware set of one failed tail boom attachment point
(barrel nut, retainer, bolt, countersunk washer, and plain washers).
Remove the barrel nut and retainer from service as applicable to the
affected tail boom attachment point. Visually inspect the removed bolt
for any corrosion, damaged threads, wear, and fatigue cracking. If the
bolt has any corrosion, a damaged thread, wear, or fatigue cracking,
before further flight, remove the bolt from service.
(B) Install a new bolt or reinstall the existing bolt, as applicable, and
a new nickel alloy barrel nut P/N NAS577C9A, NAS577C8A, or NAS577C6A,
and new retainer P/N NAS578C9A, NAS578C8A, or NAS578C6A, with the P/N
of the new nickel alloy barrel nut and the P/N of the new retainer
being as applicable to the affected tail boom attachment point by
following the Accomplishment Instructions, part I, paragraphs 6 and 7,
paragraphs 11 and 12, or paragraphs 16 and 17, of ASB 212-21-166 Rev
A, ASB 412-21-187 Rev A, or ASB 412CF-21-72 Rev A, as applicable to
your helicopter model and with the paragraphs as applicable to that
bolt. Repeat the actions required by paragraphs (g)(2)(i)(A) and (B)
of this AD for each failed tail boom attachment point, one hardware
set at a time. Then repeat the actions required by paragraph (g)(2) of
this AD just for each newly installed or reinstalled bolt until the
torque for all four tail boom attachment points stabilizes.
(ii) If the torque for all four tail boom attachment points has stabil-
ized, before further flight, apply a torque stripe to all four bolts.
(3) For the helicopter identified in paragraph (c)(4) of this AD, within 5
hours TIS after the effective date of this AD, inspect the torque
applied on each bolt in accordance with the Accomplishment
Instructions, part II, paragraphs 1 and 2, of ASB 412-21-187 Rev A.
Thereafter, repeat the torque inspection of each bolt after
accumulating 1 hour TIS, but not to exceed 5 hours TIS, to determine
if the torque has stabilized. Do not exceed three torque inspections
total for each bolt and accomplish the actions required by paragraphs
(g)(2)(i) and (ii) of this AD.
Note 2 to paragraph (g)(3): The Accomplishment Instructions, part II, par-
agraph 1, of ASB 412-21-187 Rev A refers to part I for allowable torque
limits; part I of ASB 412-21-187 Rev A specifies the different torque lim-
its for the different bolts.
(4) For helicopters identified in paragraphs (c)(1) through (4) of this
AD, within 600 hours TIS or 12 months, whichever occurs first after
applying torque stripes to all four bolts as required by paragraph
(g)(2)(ii) of this AD, and thereafter within intervals not to exceed
600 hours TIS or 12 months, whichever occurs first; and for
helicopters identified in paragraph (c)(5) of this AD, within 600
hours TIS or 12 months after the effective date of this AD, whichever
occurs first, and thereafter within intervals not to exceed 600 hours
TIS or 12 months, whichever occurs first, using the torque value
information in the Accomplishment Instructions, part II, paragraph 1,
of ASB 212-21-166 Rev A, ASB 412-21-187 Rev A, or ASB 412CF-21-72 Rev
A, as applicable to your helicopter model, inspect the torque applied
on each bolt. If the torque on any bolt is below the minimum allowable
torque limit, accomplish the actions required by paragraphs (g)(4)(i)
and (ii) of this AD.
(i) Before further flight, remove the hardware set of one failed tail boom
attachment point (barrel nut, retainer, bolt, countersunk washer, and
plain washers). Visually inspect the removed barrel nut for cracking,
corrosion, and loss of tare torque. If the barrel nut has any
cracking, corrosion, or has lost any tare toque, before further
flight, remove the barrel nut and retainer from service and replace
them with a new nickel alloy barrel nut P/N NAS577C9A, NAS577C8A, or
NAS577C6A, and new retainer P/N NAS578C9A, NAS578C8A, or NAS578C6A,
with the P/N of the new nickel alloy barrel nut and the P/N of the new
retainer being as applicable to the affected tail boom attachment
point. Regardless of the result of the barrel nut inspection, remove
the bolt from service and replace it with a new bolt by following the
Accomplishment Instructions, part I, paragraphs 6 and 7, paragraphs 11
and 12, or paragraphs 16 and 17, of ASB 212-21-166 Rev A, ASB 412-21
-187 Rev A, or ASB 412CF-21-72 Rev A, as applicable to your helicopter
model and with the paragraphs as applicable to that bolt. Repeat the
actions required by this paragraph for each failed tail boom
attachment point, one hardware set at a time.
(ii) After accumulating 1 hour TIS, but not to exceed 5 hours TIS after
accomplishing the actions required by paragraph (g)(4)(i) of this AD,
using the torque value information in the Accomplishment
Instructions, part II, paragraph 1, of ASB 212-21-166 Rev A, ASB 412
-21-187 Rev A, or ASB 412CF-21-72 Rev A, as applicable to your
helicopter model, inspect the torque applied on each newly installed
bolt. Thereafter, repeat the torque inspection of those bolts after
accumulating 1 hour TIS, but not to exceed 5 hours TIS, to determine
if the torque has stabilized. Do not exceed three torque inspections
total for those bolts and accomplish the actions required by
paragraphs (g)(2)(i) and (ii) of this AD.
Note 3 to paragraph (g)(4): The Accomplishment Instructions, part II, par-
agraph 1, of ASB 212-21-166 Rev A, ASB 412-21-187 Rev A, and ASB 412CF-21
-72 Rev A, each refer to part I for allowable torque limits; part I of ASB
212-21-166 Rev A, ASB 412-21-187 Rev A, and ASB 412CF-21-72 Rev A, specify
the different torque limits for the different bolts.
(5) Within the compliance times specified in Table 1 to the introductory
text of paragraph (g)(5) of this AD, accomplish the actions required
by paragraphs (g)(5)(i) through (iv) of this AD.
______________________________________________________________________
TABLE 1 TO THE INTRODUCTORY TEXT OF PARAGRAPH (G)(5)
______________________________________________________________________
HELICOPTER GROUPS COMPLIANCE TIMES
______________________________________________________________________
For helicopters identified in Within 5,000 hours TIS or 5 years
paragraphs (c)(l) and (2) of after accomplishing the actions re-
this AD, and helicopters quired by paragraph (g)(l) of this
identified in paragraph (c)(3) AD, whichever occurs first, and
of this AD that accomplished thereafter, within intervals not to
paragraph (g)(1)(i) of this AD. exceed 5,000 hours TIS or 5 years,
whichever occurs first.
For helicopters identified in Before the helicopter accumulates
paragraph (c)(3) of this AD 5,000 total hours TIS or 5 years
that accomplished paragraph since new, whichever occurs first,
(g)(1)(ii) of this AD. and thereafter, within intervals not
to exceed 5,000 hours TIS or 5
years, whichever occurs first.
For helicopters identified in Before the helicopter accumulates
paragraphs (c)(4) and (5) of 5,000 total hours TIS or 5 years
this AD. since new, whichever occurs first,
or if the total hours TIS or age of
the helicopter is unknown, before
further flight, and thereafter,
within intervals not to exceed 5,000
hours TIS or 5 years, whichever
occurs first.
______________________________________________________________________
(i) Remove the upper LH bolt from service and replace it with a new upper
LH bolt by following the Accomplishment Instructions, part I, para-
graphs 6 and 7, of ASB 212-21-166 Rev A, ASB 412-21-187 Rev A, or ASB
412CF-21-72 Rev A, as applicable to your helicopter model. Then accom-
plish the actions required by paragraph (g)(5)(v) of this AD.
Note 4 to paragraph (g)(5)(i): This note applies to paragraphs (g)(5)(i)
through (v) of this AD. The Accomplishment Instructions, part II,
paragraph 1, of ASB 212-21-166 Rev A, ASB 412-21-187 Rev A, and ASB 412CF
-21-72 Rev A, each refer to part I for allowable torque limits; part I of
ASB 212-21-166 Rev A, ASB 412-21-187 Rev A, and ASB 412CF-21-72 Rev A,
specify the different torque limits for the different bolts.
(ii) With the upper RH bolt removed, visually inspect the upper RH bolt
for any corrosion, damaged threads, wear, and fatigue cracking. If
the upper RH bolt has any corrosion, a damaged thread, wear, or
fatigue cracking, before further flight, remove the upper RH bolt
from service. Install a new upper RH bolt or reinstall the existing
upper RH bolt, as applicable, by following the Accomplishment
Instructions, paragraphs 11 and 12 of ASB 212-21-166 Rev A, ASB 412
-21-187 Rev A, or ASB 412CF-21-72 Rev A, as applicable to your
helicopter model. Then accomplish the actions required by paragraph
(g)(5)(v) of this AD.
(iii) With the lower LH bolt removed, visually inspect the lower LH bolt
for any corrosion, damaged threads, wear, and fatigue cracking. If
the lower LH bolt has any corrosion, a damaged thread, wear, or
fatigue cracking, before further flight, remove the lower LH bolt
from service. Install a new lower LH bolt or reinstall the existing
lower LH bolt, as applicable, by following the Accomplishment
Instructions, paragraphs 16 and 17 of ASB 212-21-166 Rev A, ASB 412
-21-187 Rev A, or ASB 412CF-21-72 Rev A, as applicable to your
helicopter model. Then accomplish the actions required by paragraph
(g)(5)(v) of this AD.
(iv) With the lower RH bolt removed, visually inspect the lower RH bolt
for any corrosion, damaged threads, wear, and fatigue cracking. If
the lower RH bolt has any corrosion, a damaged thread, wear, or
fatigue cracking, before further flight, remove the lower RH bolt
from service. Install a new lower RH bolt or reinstall the existing
lower RH bolt, as applicable, by following the Accomplishment
Instructions, paragraphs 16 and 17 of ASB 212-21-166 Rev A, ASB 412
-21-187 Rev A, or ASB 412CF-21-72 Rev A, as applicable to your
helicopter model. Then accomplish the actions required by paragraph
(g)(5)(v) of this AD.
(v) After accumulating 1 hour TIS, but not to exceed 5 hours TIS after
accomplishing the actions required by paragraph (g)(5)(i), (ii),
(iii), or (iv) of this AD, using the torque value information in the
Accomplishment Instructions, part II, paragraph 1, of ASB 212-21-166
Rev A, ASB 412-21-187 Rev A, or ASB 412CF-21-72 Rev A, as applicable
to your helicopter model, inspect the torque applied on each bolt.
Thereafter, repeat the torque inspection of those bolts after
accumulating 1 hour TIS, but not to exceed 5 hours TIS, to determine
if the torque has stabilized. Do not exceed three torque inspections
total for those bolts and accomplish the actions required by
paragraphs (g)(2)(i) and (ii) of this AD.
(6) For helicopters identified in paragraph (c) of this AD, as of the
effective date of this AD, do not install a steel alloy barrel nut P/N
NAS577B9A, P/N NAS577B8A, or P/N NAS577B6A on any helicopter.
(h) SPECIAL FLIGHT PERMIT
A one-time special flight permit may be issued in accordance with 14
CFR 21.197 and 21.199 in order to fly to a maintenance area to perform
the required actions in this AD.
(i) ALTERNATIVE METHODS OF COMPLIANCE (AMOCS)
(1) The Manager, Central Certification Branch, FAA, has the authority to
approve AMOCs for this AD, if requested using the procedures found in
14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to
your principal inspector or local Flight Standards District Office, as
appropriate. If sending information directly to the manager of the
Central Certification Branch, send it to the attention of the person
identified in paragraph (j) of this AD. Information may be emailed to
AMOC@faa.gov.
(2) Before using any approved AMOC, notify your appropriate principal in-
spector, or lacking a principal inspector, the manager of the local
flight standards district office/certificate holding district office.
(j) ADDITIONAL INFORMATION
For more information about this AD contact Jacob Fitch, Aviation Safe-
ty Engineer, FAA, 1801 S Airport Road, Wichita, KS 67209; phone: (817)
222-4130; email: jacob.fitch@faa.gov.
(k) MATERIAL INCORPORATED BY REFERENCE
(1) The Director of the Federal Register approved the incorporation by
reference of the material listed in this paragraph under 5 U.S.C. 552
(a) and 1 CFR part 51.
(2) You must use this material as applicable to do the actions required by
this AD, unless the AD specifies otherwise.
(i) Bell Alert Service Bulletin 212-21-166, Revision A, dated February 23,
2022.
(ii) Bell Alert Service Bulletin 412-21-187 Revision A, dated February 23,
2022.
(iii) Bell Alert Service Bulletin 412CF-21-72, Revision A, dated February
23, 2022.
(3) For Bell material identified in this AD, contact Bell Textron Inc., PO
Box 482, Fort Worth, TX 76101; phone (450) 437-2862 or 1-800-363-8023;
fax: (450) 433-0272; email: productsupport@bellflight.com; or website:
bellflight.com/support/contact-support.
(4) You may view this material at the FAA, Office of the Regional Counsel,
Southwest Region, 10101 Hillwood Parkway, Room 6N-321, Fort Worth, TX
76177. For information on the availability of this material at the FAA
call (817) 222-5110.
(5) You may view this material at the National Archives and Records Admin-
istration (NARA). For information on the availability of this material
at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or
email fr.inspection@nara.gov.
Issued on September 27, 2024. Victor Wicklund, Deputy Director, Compliance
& Airworthiness Division, Aircraft Certification Service.
FOR FURTHER INFORMATION CONTACT: Jacob Fitch, Aviation Safety Engineer,
FAA, 1801 S Airport Road, Wichita, KS 67209; phone: (817) 222-4130; email:
jacob.fitch@faa.gov.
|
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2024-0768; Project Identifier AD-2022-00504-R;
Amendment 39-22825; AD 2024-16-19]
RIN 2120-AA64
Airworthiness Directives; Bell Textron Inc. Helicopters
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
-----------------------------------------------------------------------
SUMMARY: The FAA is adopting a new airworthiness directive (AD)
for
certain Bell Textron Inc. Model 212, 412, 412CF, and 412EP helicopters.
This AD was prompted by reports of cracked tail boom attachment barrel
nuts (barrel nuts). This AD requires replacing all steel alloy barrel
nuts with nickel alloy barrel nuts, replacing or inspecting other tail
boom attachment point hardware, repetitively inspecting torque, and
repetitively replacing tail boom attachment bolts (bolts). This AD also
prohibits installing steel alloy barrel nuts. The FAA is issuing this
AD to address the unsafe condition on these products.
DATES: This AD is effective November 8, 2024.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of November 8,
2024.
ADDRESSES:
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2024-0768; 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 final rule, any comments received, and other
information. The address for Docket Operations is U.S. Department of
Transportation, Docket Operations, M-30, West Building Ground Floor,
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
Material Incorporated by Reference:
For Bell material identified in this AD, contact Bell
Textron Inc., P.O. Box 482, Fort Worth, TX 76101; phone: (450) 437-2862
or 1-800-363-8023; fax: (450) 433-0272; email:
productsupport@bellflight.com; or website: bellflight.com/support/contact-support.
You may view this material at the FAA, Office of the
Regional Counsel, Southwest Region, 10101 Hillwood Parkway, Room 6N-
321, Fort Worth, TX 76177. For information on the availability of this
material at the FAA, call (817) 222-5110. It is also available at
regulations.gov under Docket No. FAA-2024-0768.
FOR FURTHER INFORMATION CONTACT: Jacob Fitch, Aviation Safety Engineer,
FAA, 1801 S Airport Road, Wichita, KS 67209; phone: (817) 222-4130;
email: jacob.fitch@faa.gov.
SUPPLEMENTARY INFORMATION:
Background
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to certain serial-numbered
Bell Textron Inc. (Bell) Model 212, 412, 412CF, and 412EP helicopters.
The NPRM published in the Federal Register on May 8, 2024 (89 FR
38841). The NPRM was prompted by reports of cracked barrel nuts on
Model 412EP helicopters. According to Bell, the root cause for cracking
can vary from corrosion damage, high time in service, or hydrogen
embrittlement. Barrel nut cracking can also cause loss of torque on the
associated bolt and subsequent bolt cracking. Due to design
similarities, Model 212, 412, and 412CF helicopters are also affected.
In the NPRM, the FAA proposed to require, for certain serial-
numbered Model 212, 412CF, 412, and 412EP helicopters, replacing the
upper left-hand (LH) steel alloy barrel nut and bolt with a new nickel
alloy barrel nut, retainer, and bolt. For certain other serial-numbered
Model 412 and 412EP helicopters, the FAA proposed to require removing
the upper LH steel alloy barrel nut, inspecting the removed upper LH
steel alloy barrel nut and replacing it with a nickel alloy barrel nut
and retainer, and either inspecting or replacing the upper LH bolt. For
those serial-numbered Model 212, 412, 412CF, and 412EP helicopters, the
FAA also proposed to require removing the upper right-hand (RH), lower
LH, and lower RH steel alloy barrel nuts, inspecting those removed
steel alloy barrel nuts and replacing them with new nickel alloy barrel
nuts and retainers, and either inspecting or replacing the upper RH,
lower LH, and lower RH bolts. Thereafter for those helicopters, as well
as for one additional serial-numbered Model 412/412EP helicopter, the
FAA proposed to require inspecting the torque applied on each bolt to
determine if the torque has stabilized and, depending on the results,
replacing and inspecting certain tail boom attachment point hardware
and repeating the torque inspections, or applying torque stripes. For
all applicable helicopters, the FAA proposed to require repetitively
inspecting the torque applied on each bolt within a longer-term
compliance time interval and, depending on the results, replacing and
inspecting certain tail boom attachment point hardware and repeating
the torque inspections and stabilization, or applying torque stripes.
Additionally, for all applicable helicopters, within a longer-term
compliance time interval, the FAA proposed to require repetitively
replacing the upper LH bolt and inspecting the other three bolts and,
depending on the results, taking corrective action. Following
accomplishment of those actions, the FAA proposed to require inspecting
the torque applied on each bolt to determine if the torque has
stabilized and, depending on the results, replacing and inspecting
certain tail boom attachment point hardware and repeating the torque
inspections, or applying torque stripes. Lastly, the FAA proposed to
prohibit installing steel alloy barrel nuts on any helicopter. The
FAA is issuing this AD to address the unsafe condition on these
products.
Discussion of Final Airworthiness Directive
Comments
The FAA received comments from Bell requesting changes to the
Differences Between This Proposed AD and the Service Information
section in the NPRM (the Differences Between This AD and the Referenced
Material section in this final rule). The following presents the
comments received on the NPRM and the FAA's response to each comment.
Request To Change the Torque Inspection Nomenclature
In the NPRM, the FAA explained that while the service information
specifies checking torque, the proposed AD would require inspecting the
torque. Bell requested the FAA change the torque inspection to a torque
check consistent with the terminology in its manuals and in the service
information required by this AD.
The FAA disagrees. The FAA's regulatory definition of
``maintenance'' includes inspections but does not include checks. In
certain ADs, the FAA uses the term ``check'' in limited situations when
allowing a pilot to perform actions as an exception to the FAA's
standard maintenance regulations. For this AD, the specified torque
verification requirement is a maintenance action that must be performed
by persons authorized under 14 CFR 43.3. Accordingly, this AD must use
the term ``inspection.''
Comments Regarding Torque Below Minimum Allowable Limit
In the NPRM, the FAA explained that for stabilizing the tail boom
attachment hardware torque, the service information does not specify
actions for if the torque on a bolt is below the minimum allowable
torque, and therefore the proposed AD would require several actions.
Bell stated that certain actions such as replacing the bolt, inspecting
the associated barrel but, and repeating the torque inspection, are
mandated by Bell Alert Service Bulletin (ASB) 412-21-187, Revision A,
dated February 23, 2022, part II (torque stabilization) and part III
(repetitive longer-term torque inspection) of ASB 412-21-187, Revision
A, February 23, 2022.
The torque stabilization procedures in part II of the Bell service
bulletins specify corrective action if the torque has not stabilized
after checking the torque up to three times maximum. However, the
procedures do not specify any corrective action if the torque is below
the minimum allowable torque limit as a result of any individual
instance of a torque stabilization inspection. Similarly, the
repetitive longer-term torque inspection procedures in part III of the
Bell service bulletins specify additional actions if the torque is
below the minimum allowable torque limit as a result of an inspection.
However, the FAA determined that those part III procedures are somewhat
vague and may be interpreted in more than one way. Thus, this AD
contains specific actions for addressing torque below the minimum
limits. The FAA has clarified this explanation in the Differences
Between This AD and the Referenced Material section of this final rule.
Comment Regarding the 5,000 Hours Time-in-Service (TIS) or 5 Year
Required Actions
In the NPRM, the FAA explained the proposed AD would require
replacing the upper LH bolt and visually inspecting the upper RH and
lower bolts within 5,000 hours TIS or 5 years, while the service
information did not contain those actions. Bell stated that its service
bulletins specify that the maintenance manual will be revised to
include those actions. Bell also cited the 5,000 hour/5-year inspection
in the Bell Model 412/412EP Maintenance Manual, Issue 001, dated May
31, 2023.
The FAA has revised the Differences Between This AD and the
Referenced Material in this final rule to explain that the referenced
material specifies that the 5,000 hours TIS or 5 year threshold actions
will be incorporated into the maintenance manual.
Additional Changes Made to This Final Rule
Since the NPRM published, the FAA determined that paragraph (c) of
the proposed AD incorrectly included some serial-numbered helicopters
that are not eligible for an FAA airworthiness certificate. Therefore,
the FAA has revised the applicability of this AD to remove those
helicopters. The FAA has also updated the model for serial number 37052
in paragraph (c)(4) of this AD to Model 412EP, since it is currently
registered as such.
Conclusion
The FAA reviewed the relevant data, considered any comments
received, and determined that air safety requires adopting this AD as
proposed. Accordingly, the FAA is issuing this AD to address the unsafe
condition on these products. Except for minor editorial changes and
other changes described previously, this AD is adopted as proposed in
the NPRM. None of the changes will increase the economic burden on any
operator.
Material Incorporated by Reference Under 1 CFR Part 51
The FAA reviewed the following Bell ASBs, each Revision A, and each
dated February 23, 2022. This material specifies procedures for
replacing the steel alloy barrel nuts with nickel alloy barrel nuts,
inspecting and replacing the tail boom attachment hardware, stabilizing
the tail boom attachment hardware torque, applying torque seals, and
inspecting the torque.
ASB 212-21-166 for Model 212 helicopters,
ASB 412-21-187 for Model 412/412EP helicopters, and
ASB 412CF-21-72 for Model 412CF helicopters.
This material 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.
Differences Between This AD and the Referenced Material
The referenced material specifies checking torque, whereas this AD
requires inspecting torque because that action must be accomplished by
persons authorized under 14 CFR 43.3.
When stabilizing the tail boom attachment hardware torque, the
referenced material does not clearly specify actions for each time the
torque is below the minimum limit during any torque stabilization
inspection, whereas this AD requires replacing and inspecting certain
tail boom attachment point hardware, stabilizing the torque of the
replaced hardware set, and applying a torque stripe.
This AD requires replacing each upper LH bolt with a new (zero
total hours TIS) bolt and visually inspecting the upper RH, lower LH,
and lower RH bolts within a 5,000 hours TIS or 5 year threshold,
whereas the referenced material states that these actions will be
incorporated into the maintenance manual.
Costs of Compliance
The FAA estimates that this AD affects 105 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 AD.
For the initial requirements for certain helicopters, replacing the
four steel alloy barrel nuts with new nickel alloy barrel nuts,
inspecting or replacing up to four bolts, inspecting and stabilizing
the torque, and applying torque stripes will take up to approximately
8.5 work-hours for an estimated labor cost of up to $723. The parts
cost for the four new nickel alloy barrel nuts (including retainers) is
approximately $680. The parts cost for an upper LH bolt is
approximately $196 and the parts cost for the other bolts is
approximately $89 per bolt. The parts cost to apply torque stripes is
a
nominal amount. The estimated cost for these actions is up to
approximately $1,866 per helicopter.
For all applicable helicopters, inspecting the torque applied on
each bolt will take approximately 1 work-hour for an estimated cost of
$85 per helicopter and $8,925 for the U.S. fleet, per inspection cycle.
For all applicable helicopters, replacing an upper LH bolt,
stabilizing the torque, and applying a torque stripe will take up to
approximately 5 work-hours. The parts cost for an upper LH bolt is
approximately $196 and the parts cost to apply a torque stripe is a
nominal amount. The estimated cost for these actions is up to
approximately $621 per helicopter and $65,205 for the U.S. fleet, per
replacement cycle. Inspecting one of the other bolts, stabilizing the
torque, and applying a torque stripe will take up to approximately 3.5
work-hours for an estimated cost of $298 per bolt and $31,290 for the
U.S. fleet, per inspection cycle. If required, replacing a bolt
following that inspection will take a minimal amount of additional time
and a parts cost of approximately $89.
If required as a result of failing a torque inspection, visually
inspecting a barrel nut, replacing a bolt, stabilizing the torque, and
applying a torque stripe will take up to approximately 5.5 work-hours
per failed hardware set. The parts cost for an upper LH bolt is
approximately $196 and the parts cost for the other bolts is
approximately $89 per bolt. The parts cost to apply a torque stripe is
a nominal amount. The estimated cost for these actions is $664 (upper
LH bolt) or $557 (other bolts), per failed hardware set. If required,
replacing a barrel nut following that inspection will take a minimal
amount of additional time with a parts cost for a barrel nut (including
retainer) of approximately $173.
If required as a result of failing a torque stabilization,
replacing a barrel nut, visually inspecting a bolt, stabilizing the
torque, and applying a torque stripe will take up to approximately 5.5
work-hours and the parts cost for a barrel nut (including retainer) is
approximately $73. The estimated cost for these actions is $541. If
required, replacing the bolt following that inspection will take a
minimal amount of additional time with a parts cost for an upper LH
bolt of approximately $196 and a parts cost for the other bolts of
approximately $89 per bolt.
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
This AD will not have federalism implications under Executive Order
13132. This AD will 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 above, I certify that this AD:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Will not affect intrastate aviation in Alaska, and
(3) Will 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 Amendment
Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 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:
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