DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-0237; Project Identifier AD-2023-00491-R;
Amendment 39-22853; AD 2024-19-11]
RIN 2120-AA64

Airworthiness Directives; Robinson Helicopter Company 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 all
Robinson Helicopter Company Model R44 and R44 II helicopters. This 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 AD requires
visually inspecting a certain part-numbered flex plate assembly (flex plate) and
certain part-numbered yokes, including each flex plate bolt, and
depending on the inspection results, removing an affected part from
service and replacing an affected part with an airworthy part. This AD
also requires 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
issuing this AD to address the unsafe condition on these products.

DATES: This AD is effective October 31, 2024.

ADDRESSES:

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 final rule, any comments received, and other
information. The address for Docket Operations is U.S. Department of
Transportation, Docket Operations, M-30, West Building Ground Floor,
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.

Related Material: For Robinson material identified in this AD,
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.

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:

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 issued a notice of proposed rulemaking (NPRM)
to amend 14 CFR part 39 by adding an AD that would apply to all
Robinson Helicopter Company Model R44 and R44 II helicopters. The NPRM
published in the Federal Register on February 28, 2024 (89 FR 14596).
In the NPRM, the FAA proposed to require visually inspecting a certain
part-numbered flex plate 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.

In the NPRM, the FAA also proposed to require visually inspecting
certain part-numbered yokes 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, the FAA proposed
to require visually inspecting each yoke bolt for a torque stripe,
loose fastener, loose nut, and to determine if a certain part-numbered
nut and palnut are installed. If there are any missing torque stripes,
loose fasteners, loose nuts, or if certain nuts or palnuts are not
installed, the FAA proposed to require removing the associated yoke
from service and replacing it with an airworthy yoke.

Additionally in the NPRM, the FAA proposed to require removing from
service certain part-numbered yokes that have accumulated more than 12
years or 2,200 total hours TIS, whichever occurs first since first
installation on any helicopter, and replacing them with a certain-part-
numbered yoke 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, the FAA proposed to 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,
the FAA proposed to 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 the NPRM, the FAA proposed to require torquing each bolt,
nut, and palnut using the torque value information in Appendix 1 to the
proposed AD. The FAA is issuing this AD to address the unsafe condition
on these products.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from two commenters. The following
presents the comments received on the NPRM and the FAA's response to
each comment.

Comment Supporting the NPRM

One individual commenter supported the NPRM without change.

Comments Requesting Changes to the Required Actions

Request: Robinson Helicopter Company stated the 2,200 hours TIS
requirement to replace the affected part or to perform the magnetic
particle inspection in the proposed AD corresponds with the engine
overhaul, service life limit, and interval for additional maintenance.
However, Robinson Helicopter Company stated for Model R44 Cadet
helicopters, the hours TIS requirement to replace the affected part or
to perform the magnetic particle inspection is a 2,400 hours TIS
requirement because of that model's more restrictive operating
limitations on maximum takeoff weight and engine power. Therefore,
Robinson Helicopter Company requested the FAA increase the hours TIS
interval for the replacement of the affected part or the magnetic
particle inspection to 2,400 hours TIS for Model R44 Cadet helicopters
to allow the operator to coordinate the airworthiness directive
requirements with other mandatory maintenance requirements.

FAA Response: The FAA partially agrees with the request. The FAA
disagrees with revising this final rule to refer to Model R44 Cadet
helicopters because the "Cadet" is not a recognized type-certificated
model on the FAA type certificate data sheet. However, the FAA agrees
to allow Model R44 helicopters having serial numbers (S/N) 30001 and
subsequent (also known as "Cadet" helicopters) to have 2,400 hours
TIS to replace an affected part or to perform a magnetic particle
inspection. The FAA has revised paragraphs (g)(2) and (3) of
this final rule accordingly to reflect that Model R44 helicopters
having S/Ns 30001 and subsequent, on which a yoke replacement as
specified in this final rule was not accomplished is required to remove
that yoke from service and replace it with an airworthy yoke, prior to
the accumulation of 2,400 total hours TIS or within 12 years since
first installation, whichever occurs first.

Request: Robinson Helicopter Company stated paragraph (g)(3)(i) of
the proposed AD requires the yoke to be replaced if there is any
missing cadmium plating. Robinson Helicopter Company stated cadmium
plating provides corrosion protection without complete coverage and
also can be inadvertently removed during installation and removal of
hardware. Robinson Helicopter Company further stated that the
requirement to remove the yoke if there is any missing cadmium plating
will cause the unnecessary removal of many yokes. Therefore, Robinson
Helicopter Company requested the FAA add an exception for cadmium
plating and the removal of the yoke from service due to cadmium
plating.

FAA Response: The FAA agrees and has revised this AD accordingly by
not adopting the inspection and corrective actions associated with
cadmium plating proposed in the NPRM.

Request: Robinson Helicopter Company stated paragraph (g)(1)(iii)
of the proposed AD requires ensuring that nut part number (P/N) D210-6
and palnut P/N B330-19 are installed. Robinson stated that per type
design, only the two bolts on the flex plate assembly have palnut P/N
B330-19 installed. Robinson Helicopter Company stated the wording in
the proposed AD could cause some Model R44 helicopters to replace a
yoke unnecessarily. Robinson Helicopter Company requested the FAA
revise paragraph (g)(1)(iii) of the final rule to only apply to bolts
shared with the flex plate assembly. Robinson Helicopter Company
further stated it is possible some yokes do not have nut P/N D210-6
installed and would therefore also be subject to an unnecessary yoke
replacement. Robinson Helicopter Company requested the FAA revise the
wording of paragraph (g)(1)(iii) in the final rule to remove the
reference to nut P/N D210-6.

FAA Response: The FAA agrees with these requests and revised
paragraph (g)(1)(iii) of this AD to clarify that the inspection area is
only for the flex plate assembly bolts and to remove any references to
nut P/N D210-6.

Conclusion

The FAA reviewed the relevant data, considered any comments
received, and determined that air safety requires adopting this AD as
proposed. Accordingly, the FAA is issuing this AD to address the unsafe
condition on these products. Except for minor editorial changes, any
other changes described previously, and a clarification note added to
paragraph (g)(1)(i) of this final rule, this AD is adopted as proposed
in the NPRM. None of the changes will increase the economic burden on
any operator.

Related Material

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
material also contains the information specified in Appendix 1 to this
AD, which specifies torque values, and Figure 1 to paragraph (g)(1) of
this AD, which depicts the areas for the flex plate inspection.

Costs of Compliance

The FAA estimates that this AD affects 1,725 helicopters of U.S.
registry. The FAA estimates the following costs to comply with this AD.
Labor costs are estimated at $85 per work-hour.

Visually inspecting a flex plate will 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,
will 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 will take approximately 6 work-hours and parts
will 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 will take approximately 1.5 work-hours for an
estimated cost of $128 per helicopter.

Performing a magnetic particle inspection will take approximately
1.5 work-hours for an estimated cost of $128 per helicopter.

Applying torque to one bolt, nut, and palnut will take
approximately 1 work-hour for an estimated cost of $85 per hardware set.

If required, replacing a flex plate will take approximately 1 work-
hour and parts will 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

This AD will not have federalism implications under Executive Order
13132. This AD will not have a substantial direct effect on the States,
on the relationship between the national government and the States, or
on the distribution of power and responsibilities among the various
levels of government.

For the reasons discussed above, I certify that this AD:

(1) Is not a "significant regulatory action" under Executive
Order 12866,

(2) Will not affect intrastate aviation in Alaska, and

(3) Will not have a significant economic impact, positive or
negative, on a substantial number of small entities under the criteria
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

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

The Amendment

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

PART 39--AIRWORTHINESS DIRECTIVES

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

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

Sec. 39.13 [Amended]

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