[Federal Register Volume 86, Number 140 (Monday, July 26, 2021)]
[Rules and Regulations]
[Pages 39942-39949]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-15721]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2019-0759; Product Identifier 2018-SW-075-AD; Amendment 
39-21661; AD 2021-15-14]
RIN 2120-AA64


Airworthiness Directives; Various Restricted Category Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
various restricted category helicopters, originally manufactured by 
Bell Textron Inc. (Bell). This AD was prompted by multiple events 
involving failure of the tail boom attach structure including the 
bolts. This AD requires revising the existing Rotorcraft Flight Manual 
(RFM) for your helicopter to incorporate pre-flight checks; removing 
paint and sealant, and cleaning; repetitive inspections of structural 
components that attach the tail boom to the fuselage; and depending on 
the outcome of the inspections, repairing or replacing components, or 
re-bonding the structure. The FAA is issuing this AD to address the 
unsafe condition on these products.

DATES: This AD is effective August 30, 2021.

ADDRESSES: For service information identified in this final rule, 
contact: U.S. Army Materiel Command Logistics Data Analysis Center 
(USAMC LDAC), ATTN: Equipment Publication Control Officers (EPCOs), 
Building 3305, Redeye Road, Redstone Arsenal, AL 35898-7466; phone 
(256) 955-7716 or 1-866-211-3367; email 
[email protected]; or at https://enterprise.armyerp.army.mil.
    You may also contact the following, as applicable:
    JJASPP Engineering Services, LLC, 511 Harmon Terrace, Arlington, TX 
76010; phone: (817) 465-4495; website: www.jjaspp.com.
    Northwest Rotorcraft, LLC, 1000 85th Ave. SE, Olympia, WA 98501; 
phone: (360) 754-7200; website: www.nwhelicopters.com.
    Overseas Aircraft Support, Inc., P.O. Box 898, Lakeside, AZ 85929; 
phone (928) 368-6965; fax (928) 368-6962.
    Richards Heavylift Helo, Inc., 1181 Osprey Nest Point, Orange Park, 
FL 32073.
    Rotorcraft Development Corporation, P.O. Box 430, Corvallis, MT 
59828; phone: (207) 329-2518; email: 
[email protected].
    Southwest Florida Aviation International, Inc., 28000-A9 Airport 
Road, Bldg. 101, Punta Gorda, FL 33982-9587.
    Tamarack Helicopters Inc, 2849 McIntyre Rd, Stevensville, MT 59870; 
phone: (406) 777-0144; website: www.tamarackhelicopters.com.
    WSH, LLC, 3255 S. Bodenburg LP, Palmer, AK 99645.
    You may view the related 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 on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2019-
0759; 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 AD, any comments received, and other information. The street 
address for Docket Operations is U.S. Department of

[[Page 39943]]

Transportation, Docket Operations, M-30, West Building Ground Floor, 
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Richard R. Thomas, Aerospace Engineer, 
Denver ACO Branch, Compliance & Airworthiness Division, FAA, 26805 East 
68th Ave., Room 214, Denver, CO 80249; phone: (303) 342-1080; fax: 
(303) 342-1088; email: [email protected].

SUPPLEMENTARY INFORMATION:

Discussion of the NPRM

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 by adding an AD that would apply to Model EH-1H, EH-1X, HH-
1H, HH-1N, UH-1D, UH-1M, UH-1N, and UH-1V helicopters operating under 
experimental airworthiness certificates; and restricted category type 
certificated Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B without 
Supplemental Type Certificate (STC) No. SR00026DE installed, UH-1E, UH-
1F, UH-1H, UH-1L, and UH-1P helicopters.
    The NPRM listed the type certificate holders for these restricted 
category models as Arrow Falcon Exporters Inc.; AST, Inc.; Bell; 
California Department of Forestry; Global Helicopter Technology, Inc.; 
Hagglund Helicopters, LLC; International Helicopters, Inc.; JJASPP 
Engineering Services, LLC; JTBAM, Inc.; Northwest Rotorcraft, LLC; Red 
Tail Flying Services, LLC; Richards Heavylift Helo, Inc.; Robinson Air 
Crane, Inc.; Rotorcraft Development Corporation; San Joaquin 
Helicopters; Smith Helicopters; Southwest Florida Aviation 
International, Inc.; Tamarack Helicopters, Inc., and West Coast 
Fabrications.
    The NPRM published in the Federal Register on October 31, 2019 (84 
FR 58341). The NPRM was prompted by a series of events involving 
failure of the tail boom attach structure on several restricted 
category military surplus helicopters.
    In the NPRM, the FAA proposed to require revising the existing RFM 
for your helicopter to incorporate pre-flight checks; removing paint 
and sealant, and cleaning structural components that attach the tail 
boom to the fuselage; repetitive inspections of the cleaned structural 
components; repairing scratches, nicks, gouges, tears, and corrosion 
within allowable limits; replacing structural components with non-
repairable damage, cracks, buckling, or distortion; removing loose, 
missing, or smoking rivets from service; re-bonding structures with 
dis-bonds; and removing loose bolts and self-locking nuts from service 
and replacing them with new bolts and new self-locking nuts. The FAA is 
issuing this AD to prevent separation of the tail boom from the 
helicopter, and subsequent loss of control of the helicopter.

Background of the NPRM

    In September 2013, a tail boom separated from a UH-1B helicopter 
engaged in logging operations, resulting in a fatal accident. The FAA 
notes that the National Transportation Safety Board (NTSB) Final Report 
for that accident identified the probable cause as fatigue failure of 
the upper two tail boom attach points, which resulted in the tail boom 
separating from the fuselage during logging operations.\1\ The NTSB 
noted that poor maintenance throughout the helicopter's operational 
life contributed to the accident. In addition to this accident, the FAA 
is aware of two forced landings due to tail boom attach structure 
failures: One in May 2014 on a UH-1H helicopter engaged in construction 
operations, and one in August 2018 on a UH-1F helicopter engaged in 
firefighting operations. Each of the three events involved a failure of 
the upper left-hand (LH) tail boom attach fitting. The upper LH tail 
boom attach point is the most heavily loaded of the four tail boom 
attach points.
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    \1\ The NTSB Aviation Accident Final Report for NTSB accident 
number WPR13FA411 is available on the NTSB's website at https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/88058/pdf, accessed July 1, 2021.
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Additional Background Information

    The FAA issued Special Airworthiness Information Bulletin (SAIB) 
SW-18-29 (SAIB SW-18-29) on October 1, 2018 to alert owners and 
operators of restricted category Bell Model HH-1K, UH-1A, UH-1B, UH-1E, 
UH-1F, UH-1H, UH-1L, UH-1P, TH-1F, and TH-1L helicopters to failure of 
the tail boom attach structure. SAIB SW-18-29 recommends adhering to 
the helicopter's Instructions for Continued Airworthiness, which 
includes a repetitive 100 hour time-in-service (TIS) inspection of the 
tail boom attach structure on both sides of the four attach points and 
recommends keeping the fittings on both sides of all four attach 
points, the cap angles running forward from the fuselage side fitting, 
and the longerons running aft from the tail boom side fitting, clean 
and free of paint and any non-faying sealant; and inspecting for cracks 
in the attach structure with a borescope.
    The FAA revised SAIB SW-18-29 to SAIB SW-18-29R1, dated February 
19, 2019 (SAIB SW-18-29R1), to alert all owners and operators to 
clarified paint and sealant removal procedures and simplify the wording 
of recommendations to provide clarity.

Actions Since the NPRM Was Issued

    Since the FAA issued the NPRM, the FAA determined it is necessary 
to add notes in the applicability to clarify that Southwest Florida 
Aviation International, Inc. Model SW204 and SW204HP helicopters are 
Model UH-1B helicopters, and Model SW205 helicopters are Model UH-1H 
helicopters. These notes have been added to clarify the Model SW204, 
SW204HP, and SW205 designations used by Southwest Florida Aviation 
International, Inc.
    The FAA also made edits to clarify that an owner/operator (pilot) 
may perform the required checks and must enter compliance with the 
applicable paragraph of the AD into the helicopter maintenance records 
in accordance with 14 CFR 43.9(a)(1) through (4) and 91.417(a)(2)(v). A 
pilot may perform these checks because they involve only visual checks 
and can be performed equally well by a pilot or a mechanic. These 
checks are an exception to the FAA's standard maintenance regulations.
    Also, the FAA has learned of military design improvements of the 
UH-1H over previous variants, and further analysis of these design 
improvements prompted extending the inspection intervals for the UH-1H 
and SW205 helicopters when compared to Model HH-1K, TH-1F, TH-1L, UH-
1A, UH-1B without STC No. SR00026DE installed, UH-1E, UH-1F, UH-1L, and 
UH-1P helicopters.
    Additionally, since the NPRM was issued, the type certificate held 
by San Joaquin Helicopters is now held by WSH, LLC, and the type 
certificate held by JTBAM INC., is now held by Overseas Aircraft 
Support, Inc. This final rule reflects these changes and updates the 
contact information to that of the new type certificate holders.
    Since the NPRM was published, the FAA has also removed all 
helicopter models operating under experimental airworthiness 
certificates from this final rule. The FAA has chosen to minimize 
regulations on experimental aircraft that do not have an FAA type 
certificate because of the level of the safety risk on the individual 
helicopter.
    Further, since the NPRM was published, the FAA has removed the 
wording, ``39-inch extended landing gear installed per STC SR01742NY''

[[Page 39944]]

from Figure (1) of this AD and from the required actions paragraph, 
because other STCs may also extend the gear. The FAA also revised the 
required actions paragraph to state ``retorque'' instead of 
``retighten'' regarding any replaced bolt, and revised the phrase 
``existing maintenance manual'' to instead read ``existing maintenance 
instructions.'' The FAA updated ``attach'' and ``attachment'' wording 
throughout the final rule as applicable.
    The ADDRESSES paragraph has been revised to add contact information 
for Army Publishing Directorate and to remove contact information for 
AST, Inc., and Robinson Air Crane Inc.
    Finally, as mentioned in the NPRM, the FAA still plans to conduct 
additional rulemaking to address Model UH-1B helicopters with STC No. 
SR00026DE installed.

Discussion of Final Airworthiness Directive Comments

    After the NPRM was published, the FAA received comments from four 
commenters. The following presents the comments received on the NPRM 
and the FAA's response to the comments.

Support for the NPRM

    Aircraft Structural Repair, Inc., supported the NPRM.

Comments Requesting More Information

    An individual commenter requested the FAA provide a list of active 
short fuselage models and expressed concern about availability of 
replacement parts.
    The FAA estimates the U.S fleet of short fuselage models at 75 
helicopters based on data provided by Bell and a review of FAA aircraft 
registration records. Specific short fuselage models included in this 
estimate are HH-1K, SW204, SW204HP, TH-1F, TH-1L, UH-1A, UH-1B without 
STC No. SR00026DE installed, UH-1E, UH-1F, UH-1L, and UH-1P 
helicopters. It is possible spare parts may not be readily available to 
replace parts that fail the inspection requirements of this AD; 
however, the FAA cannot base its AD action on whether spare parts are 
readily available or available at all. While every effort is made to 
avoid grounding aircraft, the FAA must address the unsafe condition.
    An individual commenter requested the FAA provide information on 
whether a similar AD is being considered for Bell Model 204B 
helicopters.
    The FAA is reviewing data to determine if this unsafe condition 
exists on additional helicopter models and may consider additional 
rulemaking if necessary.
    One commenter asked if the forced landings cited in SAIB SW-18-29R1 
involved UH-1H helicopters and if these helicopters had the following 
STCs installed: SR01196LA, SR00929SE, SR01470SE, or SR02051LA. The 
commenter stated these STCs add extra horsepower and tail rotor 
authority. The commenter requested information on whether a combination 
of these STCs allow the tail rotor control authority to exceed the 
structural limitations of the tail boom attach fittings in response to 
sharp tail rotor control inputs.
    One of the helicopters forced to land as described in SAIB SW-18-
29R1 was a UH-1H helicopter. Another helicopter was a UH-1F, which is a 
variant of the UH-1B. The UH-1H had all four of the mentioned STCs 
installed at the time of the forced landing. The data reviewed by the 
FAA indicates the cause of the failure mode is fatigue. These STCs 
alone or in combination may increase tail boom loads but those load 
increases would only marginally increase the rate at which the tail 
boom attach structure fatigues. The inspection intervals mandated in 
this AD take into account this marginal increase in the rate of 
fatigue. The FAA is not aware of any data that the occasional increased 
loads associated with these STCs would lead directly to an exceedance 
of structural margins in the absence of fatigue.

Request for the FAA To Change the Applicability of the AD

    An individual commenter requested the FAA remove Model HH-1N and 
UH-1N helicopters from the applicability paragraph of this AD stating 
these models have ``a completely different tail boom longeron and 
attach fitting.''
    The FAA agrees these models have a different tail boom attach 
structure than the other models listed in the applicability. These 
models have been removed from this AD.
    Northwest Helicopters requested the FAA change the applicability to 
remove all Model UH-1 series helicopters operating under experimental 
exhibition (EE) airworthiness certificates and requested the FAA limit 
the applicability to those models operating under restricted category 
``repetitive heavy lift operations'' or those having more than 20 
cycles per hour. Northwest Helicopters states it is unaware of any tail 
boom attach point failure on any EE Model UH-1H helicopters.
    The FAA agrees with the request to remove helicopters with an 
experimental category airworthiness certificate from the applicability. 
All helicopters with an experimental category airworthiness certificate 
have been removed from the applicability of this AD. The FAA has chosen 
to minimize regulations on experimental aircraft that do not have an 
FAA type certificate. Nonetheless, the FAA recommends that operators of 
Model UH-1 series helicopters that are listed in the applicability and 
do not have a type certificate comply with this AD. The FAA disagrees 
with limiting the applicability to those models operating under 
restricted category ``repetitive heavy lift operations'' or those 
having more than 20 cycles per hour. The FAA is not aware of any data 
indicating that tail boom attachment failures only occur on helicopters 
engaging in repetitive heavy lift operations or those having more than 
20 cycles per hour.

Request for the FAA To Change the Related Service Information Section 
of the AD

    One commenter requested the FAA add Bell Information Letter, GEN-
18-138, Revision A, dated August 9, 2018 (GEN-18-138), to this AD when 
discussing replacement of tail boom attaching bolts. The commenter 
explained GEN-18-138 notifies owners and operators that Bell recently 
superseded self-locking nuts part number (P/N) MS21042.
    The FAA partially agrees. The FAA agrees that Bell superseded the 
original series of self-locking nuts on Model HH-1K, SW204, SW204HP, 
TH-1F, TH-1L, UH-1A, UH-1B without STC No. SR00026DE installed, UH-1E, 
UH-1F, UH-1L, and UH-1P helicopters according to information provided 
by Bell to the FAA. Self-locking nut P/N NAS9926-7L supersedes the 
original self-locking nut P/N NAS679A7 for the upper LH attach point 
and self-locking nut P/N NAS679A7 supersedes the original self-locking 
nut P/N NAS679A6 for the other three attach points. The required 
actions section of this AD has been revised to require the installation 
of self-locking nut P/N NAS9926-7L or P/N NAS9926-6L whenever an attach 
bolt is replaced. The FAA disagrees that GEN-18-138 addresses the self-
locking nuts on helicopter models affected by this AD. The original 
self-locking nuts mentioned in GEN-18-138 do not include the original 
self-locking nuts on the helicopter models affected by this AD.

[[Page 39945]]

Request for the FAA To Change the Requirement To Use a Borescope for 
Inspection

    One commenter requested that the FAA limit the requirement to use a 
borescope for inspection to certain helicopters models with baggage 
compartments.
    The FAA disagrees. The FAA inspected a Model UH-1H helicopter 
without a baggage compartment and determined that while all of the 
fuselage side attach structure is visible and within arm's reach, the 
tail boom side attach structure is not. Furthermore, due to the 
equipment in the fuselage side oil cooler bay and the confined space in 
the tail boom, accessing the tail boom side structure is difficult. 
Also, the upper right hand tail boom side attach structure is located 
behind a tail rotor pitch control rod. These factors make it difficult 
to perform a thorough inspection with only a mirror and magnification.

Request for the FAA to Change the Compliance Time

    Northwest Helicopters requested the FAA adjust the inspection 
intervals to correlate with existing AD inspection intervals to 
simplify the maintenance program for restricted category helicopters 
other than ``repetitive heavy lift'' Model UH-1 series helicopters. 
Northwest Helicopters stated a current AD requires inspection of the 
main rotor blades for cracks before further flight and every 14 days or 
25 hours TIS, whichever occurs first. Northwest Helicopters stated that 
adopting the same intervals would allow both ADs to be completed at the 
same time to provide convenience.
    The FAA disagrees with the request to change the compliance time 
for inspections required by this final rule to be consistent with the 
compliance times for inspections required by AD 2018-02-07, Amendment 
39-19160 (83 FR 2361, January 17, 2018) (AD 2018-02-07). AD 2018-02-07 
requires an initial inspection within 25 hours TIS or 2 weeks, 
whichever occurs first. Thereafter, AD 2018-02-07 requires repetitive 
inspections within 25 hours TIS or 2 weeks, whichever occurs first. 
This final rule requires an initial inspection within 25 hours TIS, 
without a calendar time requirement. Thereafter, this final rule 
requires repetitive inspections for certain helicopters within 25 hours 
TIS. Owners or operators may choose to perform the inspections required 
by this AD at 2 week intervals provided the inspections occur within 
the 25 hours TIS required by this AD.

Request for the FAA To Approve an Alternative Method of Compliance 
(AMOC) to the NPRM

    One individual stated an intent to submit several UH-1H 
modifications as an AMOC explaining the modifications are less likely 
to fail than the original structure.
    The FAA agrees that the public may submit AMOC requests to the FAA 
in accordance with 14 CFR 39.19.
    One individual requested that the FAA consider the installation of 
a modified upper LH fitting tail boom attach fitting on various model 
helicopters per U.S. Army ``Modification Work Order (MWO 55-1520-211-
40/1)'' as an AMOC, stating the modified attach fitting is less likely 
to fail than the original fitting and no reported failures were noted 
for tail booms modified per MWO 55-1520211-40/1. A second individual 
questioned whether MWO 55-1520-211-40/1 would be considered as an AMOC.
    The FAA disagrees that an upper LH fitting modified in accordance 
with MWO 55-1520-211-40/1 addresses this unsafe condition. The FAA 
reviewed Letter Report, Product Improvement Test of UH-1B Tail Boom 
Fitting, RDT&E Project No. None, USATECOM Project No. 4-5-0101-04, 
dated June 29, 1966, which contains an evaluation of MWO 55-1520-211-
40/1. The FAA determined that the average total cycles accumulated on 
UH-1B helicopters affected by this AD substantially exceeds the Army 
evaluation test cycles. Therefore, the FAA concluded MWO 55-1520-211-
40/1 does not adequately address the unsafe condition.

Request for the FAA To Withdraw the NPRM

    An individual commenter requested the FAA withdraw the NPRM. The 
commenter explained that issuing this AD would add an unnecessary 
burden to operators with a negligible increase in safety and the AD is 
unnecessary based on the series of accidents and incidents discussed in 
the NPRM. The commenter stated helicopters that are operated within 
their operating limits and properly maintained are unlikely to 
experience an inflight failure before cracks are detected because of 
existing inspection guidance. The commenter also stated that in the two 
accidents cited by the FAA, the helicopter was operated in an area not 
conducive to proper maintenance and was engaged in logging operations, 
which the commenter asserts are known for exceeding the helicopter's 
torque and weight limitations.
    The FAA disagrees with the request to withdraw the NPRM. The FAA 
has concluded the existing maintenance instructions lack sufficient 
detail to minimize the risk of an in-flight failure of the tail boom 
attach structure. Further, the FAA finds the need to mandate 
inspections through issuance of an AD to correct the unsafe condition 
identified in this final rule.

Conclusion

    The FAA reviewed the relevant data, considered the comments 
received, and determined that air safety and the public interest 
require adopting this final rule with the changes described previously. 
These changes are consistent with the intent of the proposals in the 
NPRM. The FAA also determined that these changes will neither increase 
the economic burden on any operator nor increase the scope of this AD.

Related Service Information

    The FAA reviewed portions of the following related service 
information:
     Headquarters, Department of the Army, Aviation Unit and 
Intermediate Maintenance Instructions Model UH-1H/V/EH-1H/X 
Helicopters, Technical Manual TM 55-1520-210-23-1, Change 42, dated 
April 14, 2003. This service information contains tail boom hoisting/
handling instructions; hard landing, tail rotor blade strike, and 
sudden stoppage due to compressor stall tail boom inspection 
requirements; tail boom removal and installation instructions including 
attach bolt installation and tightening instructions, tail boom attach 
fitting inspection instructions, tail boom and fuselage attach fitting 
bolt hole wear limits, allowable tail boom attach fitting damage and 
corrosion repair instructions; loose attach fitting fastener inspection 
and replacement instructions; tail boom attach fitting replacement 
instructions; classification of damage as negligible, repairable or 
requiring replacement for tail boom structure including rivets, 
fasteners, tail boom attach fittings, stringers, and longerons; tail 
boom structural material specifications; allowable area for damage 
repair of tail boom attach fittings; longeron damage limits and repair 
criteria; and stringer repair instructions.
     Headquarters, Department of the Army, Aviation Unit 
Maintenance and Aviation Intermediate Maintenance Manual for General 
Aircraft Maintenance (Sheet Metal Shop Practices) Volume 10, Technical 
Manual TM 1-1500-204-23-10, Change 3, dated August 20, 2004. This 
service information contains general information pertaining to the 
repair of aircraft structures, structural metals,

[[Page 39946]]

forming of replacement structure, rivets and riveting techniques, 
airframe sheet metal repair, and sandwich construction repair.
     Headquarters, Department of the Army, Rotorcraft 
Development Corporation, UH-1B Aircraft Preventive Maintenance 
Services, Technical Manual TM 55-1520-219-PMS, Change 7, dated August 
9, 1976. This service information contains requirements to inspect the 
tail boom attach bolts for security and the fittings for cracks daily 
and every 25, 50, 75, and 100 flight hours; and to inspect the tail 
boom interior structure and longerons for damage, cracks, and corrosion 
every 100 flight hours.
     Headquarters, Department of the Army, UH-1B DS and GS 
Maintenance Manual, Technical Manual TM 55-1520-219-34, Change 9, dated 
June 5, 1972. This service information contains instructions to remove 
and install the tail boom; attach bolt exposed thread limits; attach 
bolt tightening instructions with instructions for manufacturing a 
special torque wrench extension; allowable tail boom attach fitting 
hole diameters; damage classifications for tail boom skin, stringers 
and longerons as negligible, reparable by patching, reparable by 
insertion, or damage necessitating replacement; and instructions for 
field manufacture of P/N 204-030-800-443, Tail Boom Assembly Cover.
     Headquarters, Department of the Army, UH-1H/V and EH-1H/X 
Aircraft Phased Maintenance Checklist, Technical Manual TM 55-1520-210-
PM, Change 22, dated May 8, 2002. This service information contains 
phased inspection requirements for the tail boom interior and fuselage 
heater compartment to check for damage, cracks, and corrosion.
     Headquarters, Department of the Army, UH-1H/V and EH-1H/X 
Aircraft Preventative Maintenance Daily Inspection Checklist, Technical 
Manual TM 55-1520-210-PMD, Change 11, dated April 11, 2003. This 
service information contains preventative daily maintenance 
instructions to be accomplished prior to the first flight of the day to 
inspect for loose or missing rivets, the tail boom attachment bolts for 
security, and tail boom attachment fittings and longerons up to 12 
inches from the fittings for cracks.
     U.S. Army Aviation and Missile Command Depot Maintenance 
Work Requirement DMWR 55-1560-222, All H-1Series Tailboom Structural 
Assemblies, Change 6, dated June 18, 2002. This service information 
contains descriptions of the tail boom structure and guidance 
explaining tail boom attach fitting structural loads; tail boom 
differences between helicopter models; required depot level 
modifications; tail boom structure isometric figures identifying the 
structural components; instructions to inspect the tail boom longerons 
for dents, cracks, holes, tears, corrosion, and distortion; longeron 
repair limits and repair instructions; instructions to inspect attach 
fittings for cracks and hole elongation; attach fitting repair limits 
and repair instructions; tail boom attach fitting deburr before bonding 
to longeron instructions; and a requirement to dye penetrant inspect 
the tail boom attach fittings.
    For additional information about related service information, 
please see the published NPRM.

Differences Between This AD and the Service Information

    This AD requires the pre-flight tail boom attachment check be 
performed with a flashlight and the initial and recurring inspections 
be performed with a bright light and borescope. The service information 
does not specify any items to assist with the required checks or 
inspections. This AD requires pushing on the tail boom while performing 
certain inspections. The service information does not. On the fuselage 
side, this AD requires paying particular attention to the fitting 
sections near the rivets closest to the attach bolt, and the cap angle 
rivets next to the fittings. On the tail boom side, this AD requires 
paying particular attention to the fitting sections near the rivets 
closest to the attach bolt. The service information does not single out 
these fitting sections. This AD requires removing any cracked 
components from service, while the service information allows stop 
drilling of certain cracks. This AD requires removing any loose attach 
bolts and their self-locking nuts from service and replacing them with 
new bolts and new self-locking nuts. The service information does not 
require replacement of any loose attach bolts.

Costs of Compliance

    The FAA estimates that this AD affects 359 helicopters of U.S. 
registry. The FAA estimates that operators may incur the following 
costs in order to comply with this AD. Labor costs are estimated at $85 
per work-hour.
    Revising the existing RFM for your helicopter takes about 0.5 work-
hour, for an estimated cost of $43 per helicopter and $15,437 for the 
U.S. fleet. The pre-flight check before each flight takes about 0.25 
work-hour, for an estimated cost of $21 per helicopter per check and 
$7,539 for the U.S. fleet per check. The pre-flight check before first 
flight of the day takes about 0.5 work-hour, for an estimated cost of 
$43 per helicopter per check and $15,437 for the U.S. fleet per check.
    Removing excess paint and sealant, and cleaning all eight tail boom 
attach fittings takes about 5 work-hours and has a nominal materials 
cost, for an estimated cost of $425 per helicopter per instance and 
$152,575 for the U.S. fleet per instance.
    Inspecting all four tail boom attach points for scratches, nicks, 
gouges, tears, corrosion, cracks, bond separation, loose, missing, and 
smoking rivets, buckling, distortion, attach bolt exposed threads, and 
attach bolt movement takes about 4 work-hours, for an estimated cost of 
$340 per helicopter per inspection and $122,060 for the U.S. fleet per 
inspection.
    Inspecting only the upper LH tail boom attach point for scratches, 
nicks, gouges, tears, corrosion, cracks, bond separation, loose, 
missing, and smoking rivets, buckling, distortion, attach bolt exposed 
threads, and attach bolt movement takes about 0.5 work-hour, for an 
estimated cost of $43 per helicopter per inspection.
    The FAA cannot estimate the costs to do any allowable repair based 
on the results of the inspections and the FAA has no way of determining 
the number of helicopters that might need repair.
    The FAA estimates the following costs to do any necessary 
replacements based on the results of the inspections. The FAA has no 
way of determining the number of helicopters that might need these 
replacements.
     Replacing a tail boom attach fitting takes about 33 work-
hours and parts cost about $1,500 for an estimated cost of $4,305.
     Replacing a tail boom attach fitting, longeron, and 
doubler (longeron bond assembly) takes about 42 work-hours and parts 
cost about $7,000 (rebuilt) or $21,270 (new) for an estimated cost of 
$10,570 (rebuilt) or $24,840 (new parts).
     Replacing a fuselage attach fitting takes about 45 work-
hours and parts cost about $1,838 for an estimated cost of $5,663.
     Replacing a fuselage cap angle takes about 42 work-hours 
and parts cost about $1,827 for an estimated cost of $5,397.
     Replacing an attach bolt and self-locking nut takes about 
1 work-hour and parts cost about $313 for an estimated cost of $398.

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

[[Page 39947]]

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 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.

Adoption of 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

0
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]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

2021-15-14 Various Restricted Category Helicopters: Amendment 39-
21661; Docket No. FAA-2019-0759; Product Identifier 2018-SW-075-AD.

(a) Effective Date

    This airworthiness directive (AD) is effective August 30, 2021.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to various restricted category helicopters 
originally manufactured by Bell Textron Inc., (Bell) certificated in 
any category, including but not limited to:
    (1) Rotorcraft Development Corporation Model HH-1K helicopters;
    (2) Robinson Air Crane Inc.; Rotorcraft Development Corporation; 
and Tamarack Helicopters, Inc., Model TH-1F helicopters;
    (3) Bell; Overseas Aircraft Support, Inc. (type certificate 
previously held by JTBAM, Inc.); and Rotorcraft Development 
Corporation Model TH-1L helicopters;
    (4) Richards Heavylift Helo, Inc., Model UH-1A helicopters;
    (5) International Helicopters, Inc.; Overseas Aircraft Support, 
Inc.; Red Tail Flying Services, LLC; Richards Heavylift Helo, Inc.; 
Rotorcraft Development Corporation; Southwest Florida Aviation 
International, Inc.; and WSH, LLC (type certificate previously held 
by San Joaquin Helicopters), Model UH-1B helicopters without 
Supplemental Type Certificate (STC) No. SR00026DE installed;
    Note 1 to paragraph (c)(5): Helicopters with an SW204 or SW204HP 
designation are Southwest Florida Aviation International, Inc., 
Model UH-1B helicopters.
    (6) Bell; Overseas Aircraft Support, Inc.; Rotorcraft 
Development Corporation; Smith Helicopters; and West Coast 
Fabrications Model UH-1E helicopters;
    (7) AST, Inc.; California Department of Forestry; Robinson Air 
Crane, Inc.; Rotorcraft Development Corporation; and Tamarack 
Helicopters, Inc., Model UH-1F helicopters;
    (8) Arrow Falcon Exporters Inc.; Global Helicopter Technology, 
Inc.; Hagglund Helicopters, LLC; JJASPP Engineering Services, LLC; 
Northwest Rotorcraft, LLC; Overseas Aircraft Support, Inc.; Richards 
Heavylift Helo, Inc.; Rotorcraft Development Corporation; Southwest 
Florida Aviation International, Inc.; and Tamarack Helicopters, 
Inc., Model UH-1H helicopters;
    Note 2 to paragraph (c)(8): Helicopters with an SW205 
designation are Southwest Florida Aviation International, Inc., 
Model UH-1H helicopters.
    (9) Bell; Overseas Aircraft Support, Inc.; and Rotorcraft 
Development Corporation Model UH-1L helicopters; and
    (10) Robinson Air Crane, Inc.; and Rotorcraft Development 
Corporation Model UH-1P helicopters.

(d) Subject

    Joint Aircraft System Component (JASC): 5302, Rotorcraft Tail 
Boom.

(e) Unsafe Condition

    This AD was prompted by multiple events involving failure of the 
tail boom attach structure, including the bolts. The FAA is issuing 
this AD to address fatigue cracking of tail boom attach fittings, 
cap angles, longerons, and bolts. The unsafe condition, if not 
addressed, could result in 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) Before further flight, revise the limitations section of the 
existing Rotorcraft Flight Manual (RFM) for your helicopter by 
adding the information in Figure 1 to paragraph (g)(1) of this AD or 
by inserting a copy of this AD. The action required by this 
paragraph and the checks required by Figure 1 to paragraph (g)(1) of 
this AD may be done by the owner/operator (pilot) holding at least a 
private pilot certificate and must be entered into the aircraft 
records showing compliance with this AD by following 14 CFR 43.9 
(a)(1) through (4) and 14 CFR 91.417(a)(2)(v). The record must be 
maintained as required by 14 CFR 91.417, 121.380, or 135.439.
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[GRAPHIC] [TIFF OMITTED] TR26JY21.000

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    (2) Within 25 hours time-in-service (TIS):
    (i) Open the oil cooler/baggage compartment door on the right 
hand side of the helicopter to gain access to the interior of the 
tail boom.
    (ii) Remove paint and stray sealant and clean the eight attach 
fittings (four on the tail boom side and four on the fuselage side). 
Remove paint and stray sealant and clean the four cap angles, 
forward of the fuselage fittings, for at least 12 inches from the 
end of the fittings. Remove paint and stray sealant and clean the 
four longerons, aft of the tail

[[Page 39949]]

boom fittings, for at least 12 inches from the end of the fittings. 
It is only necessary to remove the topcoat. Primer may be left in 
place and edge and fillet sealant may be left in place. If any 
primer or edge or fillet sealant is removed, before further flight, 
reapply the removed primer and sealant.
    Note 3 to paragraph (g)(2)(ii): On some models, the baggage 
compartment floor and net must be removed to gain access to the 
lower fuselage attach fittings and cap angles.
    (iii) With an additional person pushing on the tail boom at the 
third vertical rivet line aft of the trailing edge of the elevator 
with both hands and gradually applying and relieving pressure using 
body weight a minimum of three times in each of the following 
directions: Inboard pushing from the left; inboard pushing from the 
right; and upward pushing from the bottom; and using a bright light 
and borescope, inspect each of the four tail boom attach structures 
for cracks, bond separation, and loose rivets. On the fuselage side, 
inspect the fittings and the cap angles running forward from the 
fittings, paying particular attention to the fitting sections near 
the rivets closest to the attach bolts and the cap angle rivets next 
to the fittings. On the tail boom side, inspect the fittings and the 
longerons running aft from the fittings, paying particular attention 
to the fitting sections near the rivets closest to the attach bolts. 
Without pushing on the tail boom, and using a bright light and 
borescope, inspect each of the four tail boom attach structures for 
scratches, nicks, gouges, tears, corrosion, buckling, and 
distortion, and for loose, missing, and smoking rivets. If there are 
any scratches, nicks, gouges, tears, or corrosion within allowable 
limits, before further flight, repair the affected components. If 
there are any scratches, nicks, gouges, tears, or corrosion that 
exceed allowable limits, or any cracks, buckling or distortion, or 
loose, missing, or smoking rivets, before further flight, remove the 
affected components from service. If there is any bond separation, 
before further flight, re-bond the affected components.
    Note 4 to paragraph (g)(2)(iii): It is not required to push on 
the tail boom if it cannot be reached from ground level while 
inspecting for cracks, bond separation, and loose rivets.
    (iv) Inspect each of the four tail boom attach bolts for exposed 
threads. If there is less than one full thread or more than three 
threads exposed, before further flight, remove the bolt and self-
locking nut from service and replace with a new bolt and new self-
locking nut. Self-locking nuts on Model HH-1K, SW204, SW204HP, TH-
1F, TH-1L, UH-1A, UH-1B without STC No. SR00026DE installed, and 
Model UH-1E, UH-1F, UH-1L, and UH-1P helicopters must be replaced 
with self-locking nut part number (P/N) NAS9926-7L at the upper 
left-hand (LH) attach point and self-locking nut P/N NAS9926-6L at 
the other three attach points.
    (v) Inspect each of the four tail boom attach bolts for movement 
by either applying the required installation torque in the 
tightening direction only, or by inspecting for torque stripe 
misalignment if present and attempting to rotate the bolt by hand. 
If a bolt is under-torqued, a torque stripe is misaligned, or a bolt 
moves, before further flight, remove the bolt and self-locking nut 
from service and replace with a new bolt and new self-locking nut. 
Self-locking nuts on Model HH-1K, SW204, SW204HP, TH-1F, TH-1L, UH-
1A, UH-1B without STC No. SR00026DE installed, UH-1E, UH-1F, UH-1L, 
and UH-1P helicopters must be replaced with self-locking nut P/N 
NAS9926-7L at the upper LH attach point and self-locking nut P/N 
NAS9926-6L at the other three attach points.
    (vi) After the first flight following any bolt replacement as 
required by paragraph (g)(iv) or (v) of this AD, retorque any 
replaced bolt by applying torque in accordance with the existing 
maintenance instructions for your helicopter in the tightening 
direction only and then apply a torque stripe on the bolt head.
    (3) For Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B without STC No. 
SR00026DE installed, UH-1E, UH-1F, UH-1L, and UH-1P helicopters and 
Southwest Florida Aviation International, Inc. Model SW204 and 
SW204HP helicopters, at intervals not to exceed 25 hours TIS, 
perform the actions required by paragraphs (g)(2)(i) through (vi) of 
this AD, except you are only required to perform the actions on the 
upper LH tail boom attach structure including the bolt.
    (4) For Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B without STC No. 
SR00026DE installed, UH-1E, UH-1F, UH-1L, and UH-1P helicopters and 
Southwest Florida Aviation International, Inc. Model SW204 and 
SW204HP helicopters, at intervals not to exceed 100 hours TIS, 
perform the actions required by paragraphs (g)(2)(i) through (vi) of 
this AD at all four tail boom attach points.
    (5) For Model UH-1H helicopters and Southwest Florida Aviation 
International, Inc. Model SW205 helicopters, at intervals not to 
exceed 150 hours TIS, perform the actions required by paragraphs 
(g)(2)(i) through (vi) of this AD on all four tail boom attach 
points.

(h) Special Flight Permit

    Special flight permits are prohibited.

(i) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Denver ACO 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 certification office, send it to the attention of the 
person identified in paragraph (j) of this AD.
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.

(j) Related Information

    For more information about this AD, contact Richard R. Thomas, 
Aerospace Engineer, Denver ACO Branch, Compliance & Airworthiness 
Division, FAA, 26805 East 68th Ave., Room 214, Denver, CO 80249; 
phone: (303) 342-1080; fax: (303) 342-1088; email: [email protected].

    Issued on July 18, 2021.
Ross Landes,
Deputy Director for Regulatory Operations, Compliance & Airworthiness 
Division, Aircraft Certification Service.
[FR Doc. 2021-15721 Filed 7-23-21; 8:45 am]
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