2021-03655. Airworthiness Directives; Robinson Helicopter Company Model R22 Series Helicopters

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Proposed rule; withdrawal.

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 Accordingly, the NPRM is withdrawn.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 [phone]; email [e-mail].

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

The Withdrawal

Accordingly, the notice of proposed rulemaking, Docket No. FAA-2005-21679, Directorate Identifier 2004-SW-33-AD, which was published in the Federal Register on June 28, 2005 (70 FR 37059), is withdrawn.

Issued on February 4, 2021.

Gaetano A. Sciortino,

Deputy Director for Strategic Initiatives, Compliance & Airworthiness Division, Aircraft Certification Service.