DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-1476; Project Identifier AD-2024-00090-T;
Amendment 39-22761; AD 2024-10-15]
RIN 2120-AA64

Airworthiness Directives; Gulfstream Aerospace Corporation
Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule; request for comments.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain Gulfstream Aerospace Corporation Model GVII-G500 and GVII-G600
airplanes. This AD was prompted by a report of a failed rear engine
mount discovered during a preflight walk-around due to visible engine
misalignment. This AD requires inspecting the left and right engine
mount points within the pylons and engine nacelles for non-conforming
hardware installation, repairing the engine mount points if necessary,
and revising the existing aircraft maintenance manual (AMM) to include
revised procedures for engine removal and installation. The FAA is
issuing this AD to address the unsafe condition on these products.

DATES: This AD is effective June 7, 2024.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of June 7, 2024.
The FAA must receive comments on this AD by July 22, 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 by
searching for and locating Docket No. FAA-2024-1476; 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 street address for Docket Operations is listed
above.
Material Incorporated by Reference:
For Gulfstream material, contact Gulfstream Aerospace
Corporation, Technical Publications Dept., P.O. Box 2206, Savannah, GA
31402-2206; telephone 800-810-4853; email pubs@gulfstream.com; website
gulfstream.com/en/customer-support.
You may view this material at the FAA, Airworthiness
Products Section, Operational Safety Branch, 2200 South 216th St., Des
Moines, WA. For information on the availability of this material at the
FAA, call 206-231-3195. It is also available at regulations.gov under
Docket No. FAA-2024-1476.

FOR FURTHER INFORMATION CONTACT: Jeffrey Johnson, Aviation Safety
Engineer, FAA, 1701 Columbia Avenue, College Park, GA 30337; phone:
404-474-5554; email: 9-ASO-ATLACO-ADs@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written data, views, or arguments
about this final rule. Send your comments to an address listed under
the ADDRESSES section. Include Docket No. FAA-2024-1476 and Project
Identifier AD-2024-00090-T at the beginning of your comments. The most
helpful comments reference a specific portion of the final rule,
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 final rule 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 final rule.

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 AD 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 AD, 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 AD. Submissions containing CBI should be sent to Jeffrey
Johnson, Aviation Safety Engineer, FAA, 1701 Columbia Avenue, College
Park, GA 30337; phone: 404-474-5554; email: 9-ASO-ATLACO-ADs@faa.gov.
Any commentary that the FAA receives that is not specifically
designated as CBI will be placed in the public docket for this
rulemaking.

Background

The FAA has received a report indicating that, on January 31, 2024,
a partially disengaged rear engine mount was discovered on an in-
service Model GVII-G600 airplane. The flight crew noticed a visible
misalignment in the pylon area adjacent to the thrust reverser during a
preflight walk-around. The misalignment was caused by the upper, aft
engine mount fastener migrating out of position in the pylon area.
Follow-on inspection revealed the hollow pin was the only hardware
holding the aft strut in place, and migration of the hollow pin out of
position was imminent, which would have resulted in the disconnection
of the strut from the airplane. The cause of the upper rear engine
mount failure was determined to be the secondary locking device (cotter
pin) not being installed, and the separation of the retaining nut from
the single strut attachment bolt, resulting in the bolt migrating out
of position. The bolt and nut were found at the bottom of the pylon,
and the required cotter pin was not located. It was believed that
during a post-production engine removal and installation performed in a
Gulfstream 145 Repair Station, using the AMM, the rear engine mount
fasteners on the airplane side were loosened to aid in engine
installation. It is probable that the aft upper strut attachment nut
was not properly reinstalled, and the required cotter pin was not
installed after the bolt and nut were installed. It was determined that
maintenance personnel did not fully comply with the AMM procedures that
were current at the time and anecdotal evidence that shows the
maintenance personnel requested assistance from the production engine
installation personnel to install the engine.
Gulfstream immediately performed technical evaluations on numerous
airplanes, discovering other non-conforming engine mount hardware
installations, but confirmed that none would have resulted in failure
of the engine mount system. However, some of the non-conformances were
found on engines installed in production. This indicates quality
escapes exist in both production engine installation and in-service
installation using the AMM procedures.
Additionally, an FAA investigation discovered numerous
discrepancies in the production engine installation procedures, along
with similar discrepancies in the AMM procedures for installing engines
post-delivery/post-certificate of airworthiness. The FAA identified
missing hardware callouts in the engine attachment instruction text,
engine attachment hardware not shown in the AMM graphics, and
inconsistencies in AMM image view labeling that could lead to
misinterpretation of hardware orientation (left and right mirror image
inconsistencies).
Failure of any single engine mount, if not addressed, could result
in the separation of an engine from the airplane and subsequent loss of
control of the airplane. The FAA is issuing this AD to address the
unsafe condition on these products.

FAA's Determination

The FAA is issuing this AD because the agency determined the unsafe
condition described previously is likely to exist or develop in other
products of the same type design.

Related Material Under 1 CFR Part 51

The FAA reviewed Gulfstream GVII-G500 Customer Bulletin No. 092 and
Gulfstream GVII-G600 Customer Bulletin No. 063, both Revision A, both
dated April 9, 2024. This material specifies procedures for performing
a one-time general visual inspection of the hardware at all engine
mounts, attach fittings, links, and struts; for non-conforming engine
mount hardware installations (including mis-oriented bolts, nuts, pins,
and washers; all required hardware; application of torque; and correct
hardware safety installations). This material also specifies reporting
findings of non-conforming hardware to Gulfstream and returning non-
conforming hardware to conforming configuration before further flight.
The FAA also reviewed the following AMM tasks for Chapter 71--
Powerplant, of Gulfstream Aerospace GVII-G500 AMM, Document Number GAC-
AC-GVII-G500-AMM-0001, Revision 18, dated March 29, 2024; and
Gulfstream Aerospace GVII-G600 AMM, Document
Number GAC-AC-GVII-G600-AMM-0001, Revision 14, dated March 29, 2024.
This material contains the following revised maintenance procedures for
engine removal and installation:
71-20-02 Engine Mount Hardware--Removal/Installation, 71-
20 Mounts;
71-21-03 Engine Forward Link Assemblies--Removal/
Installation, 71-21 Front Mounts;
71-21-04 Forward Engine Mount Assembly--Removal/
Installation, 71-21 Front Mounts;
71-22-03 Aft Engine Mount Strut Assembly--Removal/
Installation, 71-22 Rear Mounts;
71-23-05 Engine Thrust Strut--Removal/Installation, 71-23
Mounts: Support Links and Accessories; and
71-23-06 Engine Alignment Strut--Removal/Installation, 71-
23 Mounts: Support Links and Accessories.
These documents are distinct since they apply to different airplane
models.
This material is reasonably available because the interested
parties have access to it through their normal course of business or by
the means identified in the ADDRESSES section.

AD Requirements

This AD requires accomplishing the actions specified in the
material described previously, except as discussed under ``Differences
Between this AD and the Referenced Material'' and except for any
differences identified as exceptions in the regulatory text of this AD.

Differences Between This AD and the Referenced Material

The applicability of this AD is not limited to airplanes identified
in paragraph I.A., Effectivity, of Gulfstream GVII-G500 Customer
Bulletin No. 092 and Gulfstream GVII-G600 Customer Bulletin No. 063,
both Revision A, both dated April 9, 2024. The unsafe condition was
originally thought to be the result of improper maintenance procedures
during post-production engine removal and installation. Investigations
subsequent to the issuance of the original Gulfstream customer
bulletins were unable to definitively tie the unsafe condition to the
removal/installation work and have determined that the unsafe condition
could have originated during production. Therefore, this AD includes
airplanes that both have and have not had engines replaced since
production.
This AD requires inspecting the engine mount hardware installations
for conforming hardware and revising the existing AMM to include
revised maintenance procedures for engine removal and installation.
Where Gulfstream GVII-G500 Customer Bulletin No. 092 and Gulfstream
GVII-G600 Customer Bulletin No. 063, both Revision A, both dated April
9, 2024, state a compliance time of 12 months from the initial issue
date of February 15, 2024, this AD requires a compliance time of within
30 days after the effective date of this AD.

Justification for Immediate Adoption and Determination of the Effective
Date

Section 553(b)(3)(B) of the Administrative Procedure Act (APA) (5
U.S.C. 551 et seq.) authorizes agencies to dispense with notice and
comment procedures for rules when the agency, for ``good cause,'' finds
that those procedures are ``impracticable, unnecessary, or contrary to
the public interest.'' Under this section, an agency, upon finding good
cause, may issue a final rule without providing notice and seeking
comment prior to issuance. Further, section 553(d) of the APA
authorizes agencies to make rules effective in less than thirty days,
upon a finding of good cause.
An unsafe condition exists that requires the immediate adoption of
this AD without providing an opportunity for public comments prior to
adoption. The FAA has found that the risk to the flying public
justifies forgoing notice and comment prior to adoption of this rule
because failure of any single engine mount could result in separation
of the engine from the airplane. Accordingly, notice and opportunity
for prior public comment are impracticable and contrary to the public
interest pursuant to 5 U.S.C. 553(b)(3)(B).
The compliance time in this AD is shorter than the time necessary
for the public to comment and for publication of the final rule. In
addition, the FAA finds that good cause exists pursuant to 5 U.S.C.
553(d) for making this amendment effective in less than 30 days, for
the same reasons the FAA found good cause to forgo notice and comment.

Regulatory Flexibility Act

The requirements of the Regulatory Flexibility Act (RFA) do not
apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt
a rule without prior notice and comment. Because the FAA has determined
that it has good cause to adopt this rule without notice and comment,
RFA analysis is not required.

Costs of Compliance

The FAA estimates that this AD affects 247 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this AD:

Estimated Costs

The FAA estimates the following costs to do any necessary repairs
that would be required based on the results of the inspection. The FAA
has no way of determining the number of aircraft that might need this
repair:

On-Condition Costs

* Estimate includes two highest-cost hardware locations: thrust strut and link assembly. Although more locations are possible, two locations are used in this estimate based on typical fleet findings to date.

The FAA has included all known costs in its cost estimate.
According to the manufacturer, however, some or all of the costs of
this AD may be covered under warranty, thereby reducing the cost impact
on affected operators.

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

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: