DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-0237; Project Identifier AD-2023-00491-R]
RIN 2120-AA64

Airworthiness Directives; Robinson Helicopter Company Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for all Robinson Helicopter Company Model R44 and R44 II helicopters.
This proposed AD was prompted by reports of a fractured clutch shaft
forward yoke (yoke) on the main rotor (M/R) drive due to fatigue
cracking. This proposed AD would require visually inspecting a certain
part-numbered flex plate assembly (flex plate) and certain part-
numbered yokes, including each yoke bolt, and depending on the
inspection results, removing an affected part from service and
replacing an affected part with an airworthy part. This proposed AD
would also require removing a certain part-numbered yoke from service
after accumulating a certain number of hours time-in-service (TIS) or a
certain number of years, or as an alternative to removing the part from
service, performing a 10X or higher power magnification visual
inspection and, if needed, a magnetic particle inspection. 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 April 15,
2024.

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 regulations.gov. Follow
the instructions for submitting comments.
Fax: (202) 493-2251.
Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.
Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2024-0237; 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, any comments received, and other
information. The street address for Docket Operations is listed above.
Related Service Information: For service information identified in
this NPRM, contact Robinson Helicopter Company, Technical Support
Department, 2901 Airport Drive, Torrance, CA 90505; phone (310) 539-
0508; fax (310) 539-5198; email robinsonheli.com">ts1@robinsonheli.com; or at
robinsonheli.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.

FOR FURTHER INFORMATION CONTACT: Eric Moreland, Aviation Safety
Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone:
(562) 627-5364; email: Eric.R.Moreland@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under ADDRESSES. Include ``Docket No. FAA-2024-0237; Project Identifier
AD-2023-00491-R'' at the beginning of your comments. The most helpful
comments reference a specific portion of the proposal, explain the
reason for any recommended change, and include supporting data. The FAA
will consider all comments received by the closing date and may amend
this proposal because of those comments.
Except for Confidential Business Information (CBI) as described in
the following paragraph, and other information as described in 14 CFR
11.35, the FAA will post all comments received, without change, to
regulations.gov, including any personal information you provide. The
agency will also post a report summarizing each substantive verbal
contact received about this NPRM.

Confidential Business Information

CBI is commercial or financial information that is both customarily
and actually treated as private by its owner. Under the Freedom of
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public
disclosure. If your comments responsive to this NPRM contain commercial
or financial information that is customarily treated as private, that
you actually treat as private, and that is relevant or responsive to
this NPRM, it is important that you clearly designate the submitted
comments as CBI. Please mark each page of your submission containing
CBI as ``PROPIN.'' The FAA will treat such marked submissions as
confidential under the FOIA, and they will not be placed in the public
docket of this NPRM. Submissions containing CBI should be sent to Eric
Moreland, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard,
Lakewood, CA 90712; phone: (562) 627-5364; email:
Eric.R.Moreland@faa.gov. Any commentary that the FAA receives which is
not specifically designated as CBI will be placed in the public docket
for this rulemaking.

Background

After receiving a report of a failed yoke in the M/R drive system,
the FAA issued Special Airworthiness Information Bulletin AIR-22-08,
dated April 11, 2022 (SAIB) to remind owners and operators of any
Robinson Helicopter Company Model R44 helicopters of the importance of
adhering to existing inspection procedures in the applicable operating
handbooks and maintenance manuals. According to Robinson Helicopter
Company, the yoke had fractured due to fatigue cracking and improper
torque at the bolt hole and the yoke cross-section.
After the FAA issued the SAIB, Robinson Helicopter Company reported
an additional incident on a Model R44 helicopter where the yoke was
fractured and separated from the drive train, again due to fatigue
cracks and improper torquing. Accordingly, the FAA
proposes to adopt a new AD for all Robinson Helicopter Company Model
R44 and R44 II helicopters to ensure adequate inspection and
maintenance of all driveshaft yokes. This condition, if not addressed,
could result in loss of M/R drive and subsequent loss of control of the
helicopter.

FAA's Determination

The FAA is issuing this NPRM after determining that the unsafe
condition described previously is likely to exist or develop on other
products of the same type design.

Related Service Information

The FAA reviewed Robinson Helicopter Company R44 Maintenance Manual
and Instructions for Continued Airworthiness, Volume 1, Chapter 2 and
Chapter 23, dated September 2023, which specifies procedures for
inspecting the yoke and flex plate of the M/R drive, removing paint,
applying torque, and performing a magnetic particle inspection. This
service information also contains the information specified in Appendix
1 to this proposed AD, which specifies torque values, and Figure 1 to
paragraph (g)(1) of this proposed AD, which depicts the areas for the
flex plate inspection.

Proposed AD Requirements in This NPRM

This proposed AD would require visually inspecting flex plate part
number (P/N) C947-1 for any loose fasteners, cracks, fretting,
corrosion, wear, and to ensure that the washers are bonded to both
sides of the flex plate arms and depending on the inspection results,
removing the flex plate from service and replacing it with an airworthy
flex plate.
This proposed AD would also require visually inspecting yoke P/N
C907-1 or C907-2 as applicable, and yoke P/N C908-1, for any cracks,
corrosion, and fretting, and depending on the inspection results,
removing the yoke from service and replacing it with an airworthy yoke.
Additionally, this proposed AD would require visually inspecting each
yoke bolt for a torque stripe, loose fastener, loose nut, and to
determine if nut P/N D210-6 and palnut P/N B330-19 are installed. If
there are any missing torque stripes, loose fasteners, loose nuts, or
if nut P/N D210-6 or palnut P/N B330-19 are not installed, this
proposed AD would require removing the associated yoke from service and
replacing it with an airworthy yoke.
This proposed AD would also require removing from service any yoke
P/N C907-1 or C907-2 that has accumulated more than 12 years or 2,200
total hours TIS, whichever occurs first since first installation on any
helicopter, and replacing it with a yoke P/N C907-1 or C907-2 that has
accumulated less than 2,200 total hours TIS or 12 years, whichever
occurs first since first installation on any helicopter. As an
alternative to replacing any yoke that has accumulated more than 12
years or 2,200 total hours TIS since first installation on a
helicopter, this proposed AD would allow removing paint from the yoke
and using 10X or higher power magnifying glass to inspect for any
crack, seam, lap, shut, missing cadmium plating, or any flaw which is
open to the surface, and depending on the inspection results, removing
the yoke from service and replacing it with an airworthy yoke. If the
yoke is not replaced as a result of the alternate inspection, this
proposed AD would require performing a magnetic particle inspection of
the yoke for any crack, seam, lap, shut, or any flaw which is open to
the surface, and depending on the inspection results, removing the yoke
from service and replacing with an airworthy yoke.
Finally, if the yoke is replaced as a result of the actions
required by this proposed AD, this proposed AD would require torquing
each bolt, nut, and palnut using the torque value information in
Appendix 1 to this proposed AD.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 1,725 helicopters of U.S. registry. The FAA estimates the
following costs to comply with this proposed AD. Labor costs are
estimated at $85 per work-hour.
Visually inspecting a flex plate would take approximately 0.25
work-hour for an estimated cost of $21 per helicopter and $36,225 for
the U.S. fleet.
Visually inspecting a yoke, including inspecting each yoke bolt,
would take approximately 1.25 work-hours for an estimated cost of $106
per helicopter and $182,850 for the U.S. fleet.
Replacing a yoke would take approximately 6 work-hours and parts
would cost approximately $890 for an estimated cost of $1,400 per
helicopter.
Removing paint and inspecting a yoke using 10X or higher power
magnifying glass would take approximately 1.5 work-hours for an
estimated cost of $128 per helicopter.
Performing a magnetic particle inspection would take approximately
1.5 work-hours for an estimated cost of $128 per helicopter.
Applying torque to one bolt, nut, and palnut would take
approximately 1 work-hour for an estimated cost of $85 per hardware
set.
If required, replacing a flex plate would take approximately 1
work-hour and parts would cost approximately $1,240 for an estimated
cost of $1,325 per helicopter.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to
issue rules on aviation safety. Subtitle I, section 106, describes the
authority of the FAA Administrator. Subtitle VII: Aviation Programs,
describes in more detail the scope of the Agency's authority.
The FAA is issuing this rulemaking under the authority described in
Subtitle VII, Part A, Subpart III, Section 44701: General requirements.
Under that section, Congress charges the FAA with promoting safe flight
of civil aircraft in air commerce by prescribing regulations for
practices, methods, and procedures the Administrator finds necessary
for safety in air commerce. This regulation is within the scope of that
authority because it addresses an unsafe condition that is likely to
exist or develop on products identified in this rulemaking action.

Regulatory Findings

The FAA determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would not
have a substantial direct effect on the States, on the relationship
between the national government and the States, or on the distribution
of power and responsibilities among the various levels of government.
For the reasons discussed above, I certify this proposed
regulation:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Would not affect intrastate aviation in Alaska, and
(3) Would not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.

The Proposed Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

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