DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2019-1060; Product Identifier 2018-CE-020-AD; Amendment
39-21141; AD 2020-12-06]
Airworthiness Directives; Gulfstream Aerospace Corporation
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
SUMMARY: The FAA is adopting a new airworthiness directive (AD)
Gulfstream Aerospace Corporation (Gulfstream) Model G-IV airplanes.
This AD was prompted by reports of un-commanded nose wheel steering
turns. This AD requires replacing the nose wheel steering servo valve
manifold, incorporating revised operating procedures into the airplane
flight manual (AFM), doing a records inspection for any incidents of
un-commanded nose wheel steering turns, and reporting the results to
the FAA. The FAA is issuing this AD to address the unsafe condition on
DATES: This AD is effective July 20, 2020.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of July 20,
ADDRESSES: For service information identified in this final rule,
contact Gulfstream Aerospace Corporation, Technical Publications Dept.,
P.O. Box 2206, Savannah, Georgia 31402-2206; telephone: (800) 810-4853;
fax 912-965-3520; email: email@example.com; internet: https://www.gulfstream.com/customer-support.
You may view this service
information at the FAA, Airworthiness Products Section, Operational
Safety Branch, 901 Locust, Kansas City, Missouri 64106. For information
on the availability of this material at the FAA, call (816) 329-4148.
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-2019-1060;
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, the regulatory evaluation, any comments received, and
other information. The address for Docket Operations is Docket
Operations, 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: Alex Armas, Aerospace Engineer,
Atlanta ACO Branch, FAA, 1701 Columbia Avenue, College Park, Georgia
30337; phone: (404) 474-5538; fax: (404) 474-5605; email:
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to all Gulfstream Model G-
IV airplanes. The NPRM was published in the Federal Register on
December 27, 2019 (84 FR 71333). The NPRM was prompted by reports of
un-commanded nose wheel steering turns. An investigation revealed the
supplier compromised the seals during assembly of the electro-hydraulic
servo valves, which allows moisture to enter the valve. During cold
soak conditions, the moisture forms ice crystals in the servo valve
armature air gaps, which may cause the valve armature to displace to a
non-neutral position. This condition, if not addressed, could result in
an un-commanded nose wheel position once power is applied to the nose
wheel servo and subsequent lateral runway departure. To address this
condition, the supplier improved their production quality control
process to reduce the risk of compromised seals in the nose wheel
steering servo valve. Gulfstream also revised the normal, abnormal, and
emergency procedures in the AFMs related to nose wheel steering un-
Accordingly, this AD requires replacing the nose wheel steering
servo valve manifold, incorporating revised operating procedures into
the AFM, doing a records inspection for any incidents of un-commanded
nose wheel steering turns, and reporting the results to the FAA. The
FAA is issuing this AD to address the unsafe condition on these
The FAA gave the public the opportunity to participate in
developing this final rule. The following presents the comment received
on the NPRM and the FAA's response to the comment.
Request To Add Crew Training Verbiage
Gulfstream requested the FAA add verbiage to the preamble
referencing training that Gulfstream developed for the un-commanded
nose wheel steering issue. Gulfstream stated the flight crew training
is an important mitigation component should an aircraft experience an
un-commanded nose wheel steering turn during landing.
The FAA disagrees. The reduction in risk associated with
incorporation of the flight crew training verbiage is minimal. The
sudden and unpredicted nature of an un-commanded nose wheel steering
event allows for little to no response from the flight crew, even with
the related training. The primary means of mitigation for an un-
commanded nose wheel steering event is replacement of the nose wheel
steering valve manifold assembly, which will prevent un-commanded turns
from occurring. The FAA did not change this AD based on this comment.
The FAA reviewed the relevant data, considered the comment
received, and determined that air safety and the public interest
require adopting this final rule as proposed.
Related Service Information Under 1 CFR Part 51
The FAA reviewed Gulfstream IV Customer Bulletin Number 244, dated
March 12, 2018; Gulfstream G300 Customer Bulletin 244, dated March 12,
2018; and Gulfstream G400 Customer Bulletin 244, dated March 12, 2018.
For the applicable airplane configuration, each customer bulletin
describes procedures for replacing the nose wheel steering servo valve
The FAA also reviewed Gulfstream IV Airplane Flight Manual,
Gulfstream Aerospace Document Number GAC-AC-GIV-OPS-0001, Revision 52,
dated October 30, 2017; Gulfstream G300 Airplane Flight Manual,
Gulfstream Aerospace Document Number GAC-AC-G300-OPS-0001, Revision 20,
dated October 30, 2017; and Gulfstream G400 Airplane Flight Manual,
Gulfstream Aerospace Document Number GAC-AC-G400-OPS-0001, Revision 20,
dated October 30, 2017. For the applicable airplane configuration, each
AFM document provides revisions to the AFM with instructions for flight
crew to follow if un-commanded nose wheel steering turns occur.
This service information 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.
Costs of Compliance
The FAA estimates that this AD will affect 425 airplanes of U.S.
The FAA estimates the following costs to comply with this AD:
||Cost per product
||Cost on U.S.
|Incorporate AFM revisions
||1 work-hour x $85 per hour =
|Replace nose wheel steering servo
||7 work-hours x $85 per hour =
|Records review and reporting
of the review results
||2 work-hours x $85 per hour =
According to the manufacturer, some
of the costs of this AD may be
covered under warranty, thereby reducing the cost impact on affected
individuals. The FAA does not control warranty coverage for affected
individuals. As a result, the FAA has included all costs in this cost
Paperwork Reduction Act
A federal agency may not conduct or sponsor, and a person is not
required to respond to, nor shall a person be subject to a penalty for
failure to comply with a collection of information subject to the
requirements of the Paperwork Reduction Act unless that collection of
information displays a currently valid OMB Control Number. The OMB
Control Number for this information collection is 2120-0056. Public
reporting for this collection of information is estimated to be
approximately 2 hours per response, including the time for reviewing
instructions, searching existing data sources, gathering and
maintaining the data needed, completing and reviewing the collection of
information. All responses to this collection of information are
mandatory. Send comments regarding this burden estimate or any other
aspect of this collection of information, including suggestions for
reducing this burden to: Information Collection Clearance Officer,
Federal Aviation Administration, 10101 Hillwood Parkway, Fort Worth, TX
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.
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
(2) Is not a ``significant rule'' under DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979), 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
Adoption of 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