DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2019-0759; Product Identifier 2018-SW-075-AD]
RIN 2120-AA64

Airworthiness Directives; Various Experimental and Restricted
Category Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for various helicopters operating under experimental airworthiness
certificates and various type certificated restricted category
helicopters. This proposed AD was prompted by multiple accidents and
incidents involving failure of the tail boom attachment structure and
bolts. This proposed AD would require revising the 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 proposing this AD
to address the unsafe condition on these products.

DATES: The FAA must receive comments on this proposed AD by December
16, 2019.

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 http://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: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590, between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays.

For AST, Inc. service information identified in this NPRM, contact:
AST, Inc., 34976 Kamph Drive NE, Albany, OR 97322.

For JJASPP Engineering Services, LLC service information identified
in this NPRM, contact: JJASPP Engineering Services, LLC, 511 Harmon
Terrace, Arlington, TX 76010; phone: (817) 465-4495; website:
www.jjaspp.com.

For Northwest Rotorcraft, LLC service information identified in
this NPRM, contact: Northwest Rotorcraft, LLC, 1000 85th Ave. SE,
Olympia, WA 98501; phone: (360) 754-7200; website:
www.nwhelicopters.com.

For Richards Heavylift Helo, Inc., service information identified
in this NPRM, contact: Richards Heavylift Helo, Inc., 1181 Osprey Nest
Point, Orange Park, FL 32073.

For Robinson Air Crane, Inc., service information identified in
this NPRM, contact: Robinson Air Crane, Inc., 230 Bermuda Beach Drive,
Ft Pierce, FL 34949; phone: (305) 302-9696.

For Rotorcraft Development Corporation service information
identified in this NPRM, contact: Rotorcraft Development Corporation,
P.O. Box 430, Corvallis, MT 59828; phone: (207) 329-2518; email:
administration@rotorcraftdevelopment.com.

For San Joaquin Helicopters service information identified in this
NPRM, contact: San Joaquin Helicopters, 1407 South Lexington Street,
Delano, CA 93215; phone: (661) 725-1898; website:
www.sjhelicopters.com.

For Southwest Florida Aviation International, Inc. service
information identified in this NPRM, contact: Southwest Florida
Aviation International, Inc., 28000-A9 Airport Road, Bldg. 101, Punta
Gorda, FL 33982-9587.

For Tamarack Helicopters Inc. service information identified in
this NPRM, contact: Tamarack Helicopters Inc, 2849 McIntyre Rd,
Stevensville, MT 59870; phone: (406) 777-0144; website:
www.tamarackhelicopters.com.

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 on the internet at http://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 NPRM, the special airworthiness information bulletins (SAIBs), the
supplemental type certificate, the regulatory evaluation, any comments
received, and other information. The street address for the Docket
Operations is listed above. Comments will be available in the AD docket
shortly after receipt.

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) 342-1085; fax:
(303) 342-1088; email: richard.r.thomas@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 the ADDRESSES section. Include "Docket No. FAA-2019-0759;
Product Identifier 2018-SW-075-AD" at the beginning of your comments.
The FAA specifically invites comments on the overall regulatory,
economic, environmental, and energy aspects of this NPRM. The FAA will
consider all comments received by the closing date and may amend this
NPRM because of those comments.

The FAA will post all comments received, without change, to http://www.
regulations.gov, including any personal information you provide.
The FAA will also post a report summarizing each substantive verbal
contact received about this NPRM.

Discussion

The FAA proposes to adopt a new AD for 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 for restricted category
type certificated Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B without STC
No. SR00026DE installed, UH-1E, UH-1F, UH-1H, UH-1L, and UH-1P
helicopters. The FAA plans to publish separate rulemaking to address
Model UH-1B with STC No. SR00026DE installed.

The type certificate holders for the restricted category models are
Arrow Falcon Exporters Inc.; AST, Inc.; Bell Helicopter Textron, Inc.;
California Department of Forestry; West Coast Fabrications; 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.; and Tamarack Helicopters, Inc.

This proposed AD would require revising the 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; replacing loose or missing
rivets; 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.

This proposed AD was prompted by a series of accidents and
incidents involving failure of the tail boom attachment structure on
several restricted category military surplus helicopters. This
condition, if not addressed, could result in separation of the tail
boom from the helicopter, and subsequent loss of control of the
helicopter.

In January 1982, a tail boom separated from a UH-1B helicopter
engaged in logging operations, resulting in a fatal accident. The
National Transportation Safety Board's (NTSB) final report identified
structural fatigue and inadequate maintenance as probable causes. In
September 2013, a tail boom separated from another UH-1B helicopter
engaged in logging operations, resulting in another fatal accident. The
NTSB's final report for that accident identified the cause as fatigue
failure of the upper two tail boom attach points. Contributing to this
accident was poor maintenance throughout the helicopter's operational
life. In addition to these accidents, the FAA is aware of three forced
landings due to tail boom attachment structure failures, one in May
2014 on a UH-1H helicopter, one in August 2016 on a UH-1H helicopter,
and one in August 2018 on a UH-1F helicopter. The helicopter involved
in the May 2014 forced landing was engaged in construction operations.
The operations the helicopter was engaged in during the August 2016
forced landing are unknown. The helicopter involved in the August 2018
forced landing was engaged in firefighting operations.

In the first fatal accident and two of the forced landings, a loud
pop or bang was heard in the rear of the aircraft at the moment of
failure. In the second fatal accident, the pilot indicated before the
flight that the helicopter felt like it "shuffled" during
translational lift. Four of the five incidents involved a failure of
the upper left hand tail boom attachment structure. In three cases it
was the attach fitting on the tail boom side. In one case it was the
longeron on the tail boom side. The upper left hand tail boom attach
point is the most heavily loaded of the four attach points.

The FAA issued Special Airworthiness Information Bulletin 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 of failure of the tail
boom attachment 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 attachment structure on
both sides of the four attachment points. SAIB SW-18-29 also specifies
the following supplemental recommendations: Keeping the fittings on
both sides of all four attachment 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 attachment structure
with a borescope since the tail boom side structure is difficult to
access. On the fuselage side, SAIB SW-18-29 recommends paying
particular attention to the most forward fitting fasteners, the cap
angle and the cap angle rivets just forward of the fitting as failures
in these areas are more common. On the tail boom side, SAIB SW-18-29
recommends paying particular attention to the most aft fitting
fasteners as failures in this area are more common. SAIB SW-18-29 also
advises that smoking rivets are an indicator of attachment point
issues. For helicopters that perform heavy lift operations, SAIB SW-18-
29 recommends performing a repetitive 20 hours TIS inspection of both
the fuselage and tail boom upper left-hand (LH) attach fittings,
fuselage side cap angle, and tail boom side longeron. Lastly, for all
affected helicopters, if a loud noise (typically a "pop" or "bang")
is heard in the rear of the aircraft during flight, SAIB SW-18-29
recommends minimizing hovering, slow flight, and pedal turns; reducing
power when possible to avoid left pedal input; jettisoning external
loads (if present) as soon as possible; and landing the aircraft as
soon as possible. If an external load must be landed, SAIB SW-18-29
recommends performing a forward descent until the load touches down.

Based on input from a repair station, 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 of clarified paint and sealant removal
procedures and simplify the wording of recommendations to provide
clarity. In particular, it was necessary to correct the emphasized
inspection areas. The fuselage side fitting emphasis was revised to
focus on the fitting section through the rivets closest to the attach
bolt (the aft fitting fasteners) rather than through the most forward
fitting fasteners. The tail boom side fitting emphasis was revised to
focus on the fitting section through the rivets closest to the attach
bolt (the forward fitting fasteners) rather than through the most aft
fitting fasteners.

Related Service Information

The FAA reviewed portions of the following related service
information:

Garlick Helicopters Inc. Instructions for Continued
Airworthiness Report No. GH-H13WE-CA1H, UH-1H Helicopters, Revision 4,
dated August 9, 2012, available from Rotorcraft Development
Corporation. This report contains a Component Overhaul Schedule, an
Airworthiness Limitation Schedule, and a Continued Airworthiness
Documents Section that lists Army Technical Manuals required for
servicing, maintaining, inspecting, repairing, and overhauling the
helicopter, its engine, rotors, and appliances, and for special purpose
modifications.

Garlick Helicopters Inc. Instructions for Continued
Airworthiness Report No. GH-H5NM-CA1, UH-1E, UH-1L, TH-1L and HH-1K
Helicopters, Revision Original, dated October 22, 2002, available from
Rotorcraft Development Corporation. This report contains a Component
Overhaul Schedule, an Airworthiness Limitation Schedule, and a
Continued Airworthiness Documents Section that lists Army Technical
Manuals required for servicing, maintaining, inspecting, repairing, and
overhauling the helicopter, its engine, rotors, appliances, and for
special purpose modifications.

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, available from JJASPP Engineering Services, LLC,
Richards Heavylift Helo, Inc., and San Joaquin Helicopters. 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 attachment bolt installation
and tightening instructions, tail boom attachment fitting inspection
instructions, tail boom and fuselage attachment fitting bolt hole wear
limits, allowable tail boom attachment fitting damage and corrosion
repair instructions; loose attachment fitting fastener inspection and
replacement instructions; tail boom attachment fitting replacement
instructions; classification of damage as negligible, repairable or
requiring replacement for tail boom structure including rivets,
fasteners, tail boom attachment fittings, stringers, and longerons;
tail boom structural material specifications; allowable area for damage
repair of tail boom attachment fittings; longeron damage limits and
repair criteria; and stringer repair instructions.

Headquarters, Department of the Army, Aviation Unit and
Intermediate Maintenance Instructions Army Model UH-1H/V/EH-1H/X,
Technical Manual TM 55-1520-210-23-3, Change 8, dated June 14, 1996,
available from JJASPP Engineering Services, LLC, Richards Heavylift
Helo, Inc., and San Joaquin Helicopters. This service information
contains: A Maintenance Allocation Chart which assigns tail boom
maintenance functions to three levels, (1) high-frequency field tasks
requiring general knowledge to maintain the helicopter in an airworthy
condition or return the helicopter to an airworthy condition, (2) low-
frequency field tasks requiring specialized knowledge to return the
helicopter to an airworthy condition, and (3) helicopter or component
maintenance tasks which cannot be performed in the field; and
instructions for field manufacture of part number (P/N) 204-030-800-
443, Tail Boom Assembly Cover, and P/N 205-031-801-53, Tail Boom Cover.

Headquarters, Department of the Army, Aviation Unit
Maintenance (AVUM) and Aviation Intermediate Maintenance (AVIM) Manual
for General Aircraft Maintenance (General Maintenance and Practices),
Volume 1, Technical Manual TM 1-1500-204-23-1, Change 5, dated May 31,
2006, available from Richards Heavylift Helo, Inc. This service
information contains general maintenance practice information.

Headquarters, Department of the Army, AVUM and AVIM Manual
for General Aircraft Maintenance (Hardware and Consumable Materials)
Volume 6, Technical Manual TM 1-1500-204-23-6, Change 4, dated August
20, 2004, available from Richards Heavylift Helo, Inc. This service
information contains general information pertaining to the use and
identification of hardware and materials, specifically bolts, nuts,
rivets, clamps, fittings, plate nuts, torque values, lockwire
techniques, cotter pins, safety pins, and Hi-Shear rivets.

Headquarters, Department of the Army, AVUM and AVIM Manual
for General Aircraft Maintenance (Nondestructive Testing and Flaw
Detection Procedures and Practices) Volume 7, Technical Manual TM 1-
1500-204-23-7, Change 1, dated December 30, 1993, available from
Richards Heavylift Helo, Inc. This service information contains general
information pertaining to nondestructive testing and flaws, and
nondestructive inspection procedures and practices, particularly
magnetic particle inspections, radiography, ultrasonic inspections, and
electromagnetic inspections.

Headquarters, Department of the Army, AVUM and AVIM 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, available from Richards Heavylift Helo, Inc. This service
information contains general information pertaining to the repair of
aircraft structures, structural metals, forming of replacement
structure, rivets and riveting techniques, airframe sheet metal repair,
and sandwich construction repair.

Headquarters, Department of the Army, AVUM and AVIM Manual
Nondestructive Inspection Procedures for UH-1 Helicopter Series,
Technical Manual TM 1-1520-256-23, dated November 30, 1996, available
from Richards Heavylift Helo, Inc. This service information contains
instructions for accomplishing an eddy current inspection of the
fuselage structure, tail boom and fuselage tail boom attachment
fittings, and tail boom longerons.

Headquarters, Department of the Army, Operator's Manual
Army Model UH-1B Helicopter, Technical Manual TM 55-1520-219-10, Change
20, dated May 16, 1983, available from Richards Heavylift Helo, Inc.,
and Rotorcraft Development Corporation. This manual contains operating
instructions and procedures for the UH-1B helicopter. It includes a
brief description of the tail boom structure.

Headquarters, Department of the Army, Operator's Manual
Army Model UH-1H/V Helicopters, Technical Manual TM 55-1520-210-10,
Change 20, dated June 23, 2005, available from Northwest Rotorcraft,
LLC, Richards Heavylift Helo, Inc., and Rotorcraft Development
Corporation. This manual contains operating instructions and procedures
for the UH-1H/V helicopter. It includes a brief description of the tail
boom structure and a pre-flight check of the tail boom attachment
bolts.

Headquarters, Department of the Army, Organizational
Maintenance Manual Army Model UH-1B Helicopter, Technical Manual TM 55-
1520-219-20, Change 28, dated August 2, 1982, available from Richards
Heavylift Helo, Inc., Rotorcraft Development Corporation, and Southwest
Florida Aviation International, Inc. This manual provides various
maintenance instructions for flight line maintenance crews, including
special inspections of the tail boom attachment structure. Following
hard landings, tail rotor blade strikes, or compressor stalls,
maintenance crews are required to inspect the area where the tail boom
attaches to the forward fuselage section, specifically the attachment
fittings, longerons and cap angles, for cracks, distortion, and loose
rivets, and the attachment bolts for torque.

Headquarters, Department of the Army, Preparation for
Shipment of UH-1/EH-1 Helicopters, Technical Manual TM 55-1520-242-S,
Change 5, dated June 30, 1993, available from JJASPP Engineering
Services, LLC. This service information contains instructions to coat
attachment points and hardware with corrosion preventive when tail boom
is removed for transport.

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, available
from Rotorcraft Development Corporation. This service information
contains requirements: To inspect the tail boom attaching 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, available from Richards Heavylift Helo, Inc., Rotorcraft
Development Corporation, and Southwest Florida Aviation International,
Inc. This service information contains: Instructions to remove and
install the tail boom; attachment bolt exposed thread limits;
attachment bolt tightening instructions with instructions for
manufacturing a special torque wrench extension; allowable tail boom
attachment 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, Changes 22, dated May 8, 2002, available from Northwest Rotorcraft,
LLC. 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, Preventive Maintenance Daily Inspection
Checklist UH-1H/V and EH-1H/X Helicopters, Change 11, dated April 11,
2003, available from JJASPP Engineering Services, LLC, and Northwest
Rotorcraft, LLC. 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.

JJASPP Engineering Services Instructions for Continued
Airworthiness for Restricted Category UH-1H Rotorcraft Report No.
JJASPP-ICA-12-005, Revision IR, approved February 6, 2013, available
from JJASPP Engineering Services, LLC. This report contains a Component
Overhaul Schedule, an Airworthiness Limitation Schedule, and a
Continued Airworthiness Documents section that list documents and
reports required for servicing, maintaining, inspecting, repairing, and
overhauling the rotorcraft, its engine, rotors, and appliances.

Northwest Rotorcraft, LLC, UH-1H Instructions for
Continued Airworthiness Report No. PH-106, Revision 7, approved March
15, 2012, available from Northwest Rotorcraft, LLC. This report
contains a Component Overhaul Schedule, an Airworthiness Limitation
Schedule, and a Continued Airworthiness Documents Section, which lists
Army Technical Manuals required for servicing, maintaining, inspecting,
repairing, and overhauling the helicopter, its engine, rotors, and
appliances, and for special purpose modifications.

Rotorcraft Development Corporation Instructions for
Continued Airworthiness Report No. GH-H3NM-CA1, UH-1B Helicopters,
Revision 1, dated December 6, 2012, available from Rotorcraft
Development Corporation. This report contains a Component Overhaul
Schedule, an Airworthiness Limitation Schedule, and a Continued
Airworthiness Documents Section that lists Army Technical Manuals
required for servicing, maintaining, inspecting, repairing, and
overhauling the helicopter, its engine, rotors, and appliances, and for
special purpose modifications.

Tamarack Helicopters, Inc., Instructions for Continued
Airworthiness Report No. ICA-1, UH-1F, UH-1P AND TH-1F Helicopters,
Revision 6, dated March 14, 2016, available from Tamarack Helicopters,
Inc. This report contains a Component Overhaul Schedule, an
Airworthiness Limitation Schedule, and a list of Air Force Technical
Orders required for servicing, maintaining, inspecting, repairing, and
overhauling the helicopter, its engine, rotors, and appliances.

Tamarack Helicopters, Inc., UH-1H Instructions for
Continued Airworthiness Report No. TAM-102, Revision Original, dated
July 23, 2009, available from Tamarack Helicopter, Inc. This report
contains a Component Overhaul Schedule, an Airworthiness Limitations
Schedule and a Continued Airworthiness Documents section, which lists
documents and reports required for servicing, maintaining, inspecting,
repairing, and overhauling the helicopter, its engine, rotors,
appliances and special purpose modifications.

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, available from JJASPP
Engineering Services, LLC. This service information contains
descriptions of the tail boom structure and guidance explaining tail
boom attachment 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 attachment fittings for
cracks and hole elongation; attachment fitting repair limits and repair
instructions; tail boom attachment fitting deburr before bonding to
longeron instructions; and a requirement to dye penetrant the tail boom
attachment fittings.

U.S. Army Aviation and Troop Command Aircraft Depot
Maintenance Work Requirement DMWR 55-1520-210, UH-1H/UH-1V Helicopters,
Change 11, dated August 31, 1994, available from Northwest Rotorcraft,
LLC, and Southwest Florida Aviation International, Inc. This higher-
level document directs maintenance personnel to DMWR 55-1560-222 for
detail depot maintenance instructions. It also contains information
regarding differences between the two models, instructions for cleaning
and corrosion control, longeron and stringer allowable damage and
repair; requirements to check tail boom for alignment; general aircraft
repair procedures; guidance explaining tail boom attachment fitting
structural loads; and guidance regarding primary vs. secondary tail
boom structure.

FAA's Determination

The FAA is proposing this AD because the FAA evaluated all the
relevant information and determined the unsafe condition described
previously is likely to exist or develop in other products of these
same type designs.

Proposed AD Requirements

This proposed AD would require revising the RFM for your helicopter
to add before each flight and before first flight of the day pre-flight
checks; removing excess paint and sealant from, and cleaning certain
tail boom attachment structures; repetitive inspections for scratches,
nicks, gouges, tears, corrosion, cracks, bond separation, loose, missing,
and smoking rivets, buckling, distortion, number of attachment bolt
exposed threads, and attachment bolt movement.

This proposed AD would require repairing scratches, nicks, gouges,
tears, and corrosion within allowable limits. This proposed AD would
require removing from service components with scratches, nicks, gouges,
tears, and corrosion that exceed allowable limits, removing from
service components with any cracks, buckling, or distortion, and
removing from service loose, missing, or smoking rivets. This proposed
AD would also require re-bonding any structure with dis-bonds, and
removing loose bolts and self-locking nuts from service, and replacing
them with new bolts and new self-locking nuts.

Differences Between This Proposed AD, the SAIB, and the Service
Information

This proposed AD differs from SAIB SW-18-29R1 by expanding the
applicability to add various model helicopters operating under
experimental airworthiness certificates due to design similarity. This
proposed AD also updates part name nomenclature from SAIB SW-18-29R1 by
using "attachment bolt" and "attachment fitting" instead of
"attach bolt" and "attach fitting."

This proposed AD would require daily checks be performed with a
flashlight and 25 hour and 100 hour TIS 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. The
proposed AD would require pushing on the tail boom while making certain
inspections. The service information does not. On the fuselage side,
this proposed AD would require paying particular attention to the
attachment fitting section near the rivets closest to the attachment
bolt, and the cap angle rivets next to the fitting. On the tail boom
side, this proposed AD would require paying particular attention to the
attachment fitting section near the rivets closest to the attachment
bolt. The service information does not single out these sections. This
proposed AD would require replacing any cracked components, while the
service information allows stop drilling of certain cracks. This
proposed AD would require removing any loose attachment 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 attachment bolts.

Costs of Compliance

The FAA estimates that this proposed AD would affect 504
helicopters of U.S. registry. Labor costs are estimated at $85 per
work-hour. Based on these numbers, the FAA estimates the following
costs to comply with this proposed AD.

Revising the RFM for your helicopter would take about 0.5 work-
hour, for an estimated cost of $43 per helicopter and $21,672 for the
U.S. fleet. The pre-flight check before each flight would take about
0.25 work-hour, for an estimated cost of $21 per helicopter per check
and $10,584 for the U.S. fleet per check. The pre-flight check before
first flight of the day would take about 0.5 work-hour, for an
estimated cost of $43 per helicopter per check and $21,672 for the U.S.
fleet per check.

Removing excess paint and sealant, and cleaning all eight tail boom
attachment fittings would take about 5 work-hours and a nominal
materials cost, for an estimated cost of $425 per helicopter per
instance and $214,200 for the U.S. fleet per instance.

Inspecting all four tail boom attachments for scratches, nicks,
gouges, tears, corrosion, cracks, bond separation, loose, missing or
smoking rivets, buckling, distortion, attachment bolt exposed thread,
and attachment bolt movement would take about 4 work-hours, for an
estimated cost of $340 per helicopter per inspection and $171,360 for
the U.S. fleet per inspection.

Inspecting only the upper left hand tail boom attachment for
scratches, nicks, gouges, tears, corrosion, cracks, bond separation,
loose, missing or smoking rivets, buckling, distortion, attachment bolt
exposed threads, and attachment bolt movement would take 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 aircraft 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 aircraft that might need these
replacements.

Replacing a tail boom attachment fitting would take about
33 work-hours and parts would cost about $1,500 for an estimated cost
of $4,305.

Replacing a tail boom longeron bond assembly (attachment
fitting, longeron, and doubler) would take about 42 work-hours and
parts would 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 attachment fitting would take about
45 work-hours and parts would cost about $1,838 for an estimated cost
of $5,663.

Replacing a fuselage cap angle would take about 42 work-
hours and parts would cost about $1,827 for an estimated cost of
$5,397.

Replacing an attachment bolt and self-locking nut would
take about 1 work-hour and parts would 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 the FAA Administrator. Subtitle VII: Aviation Programs
describes in more detail the scope of the Agency's authority.

The FAA is proposing 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 above, I certify that this proposed
regulation:

(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 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 (AD):