DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[FAA Docket No. FAA-2020-0994; Project Identifier AD-2020-00687-T]
RIN 2120-AA64

Airworthiness Directives; Gulfstream Aerospace Corporation Airplanes

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) for certain
Gulfstream Aerospace Corporation (Gulfstream) Model GVII-G600
airplanes. The NPRM was prompted by a report that a failure mode in the
data concentration network (DCN) software causes the pitch attitude
value to freeze on the primary flight display (PFD) for up to 20
seconds. The NPRM proposed to require updating the DCN and flight deck
master operating system (MOS) software. Since issuance of the NPRM, the
FAA has determined that there is not an unsafe condition because all
affected airplanes have updated software. Accordingly, the NPRM is
withdrawn.

DATES: As of June 8, 2021, the proposed rule, which published in the
Federal Register on February 23, 2021 (86 FR 10875), is withdrawn.

ADDRESSES:

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2020-0994; 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, the
regulatory evaluation, 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: Myles Jalalian, Aviation Safety
Engineer, Atlanta ACO Branch, FAA, 1701 Columbia Avenue, College Park,
GA 30337; phone: (404) 474-5572; fax: (404) 474-5606; email:
myles.jalalian@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued an NPRM that proposed to amend 14 CFR part 39 by
adding an AD that would apply to certain serial-numbered Gulfstream
Model GVII-G600 airplanes. The NPRM published in the Federal Register
on February 23, 2021 (86 FR 10875). The NPRM was prompted by a report
of a failure mode in the DCN software that causes pitch attitude value
to freeze on the PFD for up to 20 seconds, which results in temporarily
incorrect pitch indications.

The effect is evident only if the pitch of the airplane changes
during the 20 second reset window. After 20 seconds, the system returns
to normal. The standby flight display and heads up display are
unaffected by this failure mode and continue to display the correct
pitch attitude. However, there is not an alert or annunciation that
informs the flight crew of a stale (frozen) pitch display or
potentially misleading flight information.

The NPRM proposed to require installing the MOS software update
part number EB60001034-0106, updating the DCN software level to version
10.10.12 in support of the MOS software update, and operationally
checking the installations. Incorrect pitch indications could result in
the loss of control of the airplane during certain phases of flight
during instrument meteorological conditions.

Actions Since the NPRM Was Issued

After issuance of the NPRM, the FAA received a comment from
Gulfstream recommending the FAA withdraw the NPRM based on full fleet
compliance. All Gulfstream Model GVII-G600 airplanes have corrected the
unsafe condition by complying with the proposed software update. The
FAA has determined that the unsafe condition has been removed from the
fleet. In addition, since Gulfstream controls the software, it is
unlikely the unsafe condition will be re-introduced.

Based on the above information, the FAA has determined that AD
action is not warranted and the proposal should be 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.

Regulatory Findings

Since this action only withdraws an NPRM, it is neither a proposed
AD nor a final rule. This action, therefore, is not covered under
Executive Order 12866 or the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

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