DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2005-21679; Directorate Identifier 2004-SW-33-AD]
RIN 2120-AA64

Airworthiness Directives; Robinson Helicopter Company Model R22
Series Helicopters

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Proposed rule; withdrawal.

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SUMMARY: The FAA is withdrawing a notice of proposed rulemaking (NPRM)
that proposed to adopt a new airworthiness directive (AD) that would
have applied to Robinson Helicopter Company (RHC) Model R22 series
helicopters. The NPRM was prompted by an in-flight break up of a
helicopter on which both teeter stop brackets (brackets) failed. The
NPRM would have required replacing each main rotor blade (blade) droop
and teeter stop (stop) and bracket and associated hardware with
redesigned and improved airworthy parts. Since issuance of the NPRM,
the FAA has determined that failure of the brackets was caused by
turbulence and other factors that are addressed in AD 95-26-04.
Accordingly, the NPRM is withdrawn.

DATES: The FAA is withdrawing the proposed rule published June 28, 2005
(70 FR 37059), as of February 25, 2021.

ADDRESSES:

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-2005-21679;
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 action, any comments received, and other information. The
street 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.

FOR FURTHER INFORMATION CONTACT: James Guo, Aviation Safety Engineer,
Los Angeles ACO Branch, FAA, 3960 Paramount Blvd., Lakewood, California
90712; telephone 562-627-5357; email james.guo@faa.gov.

SUPPLEMENTARY INFORMATION:

Discussion

The FAA has issued an NPRM that proposed to amend 14 CFR part 39 by
adding an AD that would apply to the specified products. The NPRM was
published in the Federal Register on June 28, 2005 (70 FR 37059). The
NPRM was prompted by an accident that involved an in-flight breakup of
a helicopter that had old part-numbered stops and brackets installed.
While the probable cause of the in-flight breakup had not been
determined, the FAA believed failure of the stops or brackets may have
been a contributing factor. Accordingly, the NPRM proposed to require
replacing the stops and brackets with redesigned, airworthy parts. The
proposed actions were intended to prevent failure of the stops and
brackets, blade contact with the airframe, and subsequent loss of
control of the helicopter.

Actions Since the NPRM Was Issued

Since issuance of the NPRM, the FAA has determined that the unsafe
condition was caused by different factors than those stated in the
NPRM. Previously, RHC had introduced service information to replace the
stops and brackets that were the subject of the NPRM with redesigned
parts. The redesign introduced a material change from aluminum to
stainless steel. However, the redesigned parts were mistakenly
evaluated as a change that would address the unsafe condition. It has
since been determined that the strength increase in the redesign is
insignificant and would not have improved the outcome of the accident.
It has also been determined that the accident was caused by mast
bumping, which is addressed in AD 95-26-04 (60 FR 66487, December 22,
1995) (AD 95-26-04). Therefore, the FAA has determined that AD action
is not required and the NPRM is withdrawn.

Withdrawal of the NPRM constitutes only such action and does not
preclude the FAA from further rulemaking on this issue, nor does it
commit the FAA to any course of action in the future.

Comments

The FAA gave the public the opportunity to comment on the NPRM. The
following presents the comments received on the NPRM and the FAA's
response to each comment.

Requests

One commenter stated that the stops and droops could not have
contributed to the accident as contact with those items occurs only
when operating a Model R22 helicopter outside of its certificated
flight envelope, accordingly making it an operational issue. The
commenter requested the FAA table the proposed AD until the accident
investigation is complete.

The FAA acknowledges the commenter's request. The FAA further
determined that the unsafe condition was caused by mast bumping, which
is addressed in AD 95-26-04. Because the FAA is withdrawing the NPRM
and has issued AD 95-26-04, the commenter's request is no longer
necessary.

A second commenter requested that the proposed action be modified
by inclusion of the following or similar statement: "The requirement
to install certain part-numbered specific parts shall be interpreted
broadly to include any replacements parts approved under FAR 21.303 for
the original equipment parts cited in this action. Nothing in this
action prevents or precludes the installation of such alternatively
approved parts."

The FAA acknowledges the commenter's request. However, because the
FAA is withdrawing the NPRM, the commenter's request is no longer
necessary.

FAA's Conclusions

Upon further consideration of the available information, the FAA
has determined that the NPRM is unnecessary. Accordingly, the NPRM is
withdrawn.

Regulatory Findings

Since this action only withdraws an NPRM, it is neither a proposed
nor a final rule. This action therefore is not covered under Executive
Order 12866, the Regulatory Flexibility Act, or DOT Regulatory Policies
and Procedures (44 FR 11034, February 26, 1979).

List of Subjects in 14 CFR Part 39

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