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PROPOSED AD GULFSTREAM AEROSPACE CORPORATION: Docket No. FAA-2021-0958; Project Identifier 2019-CE-010-AD.
(a) COMMENTS DUE DATE

    The FAA must receive comments on this airworthiness directive (AD)  by
    December 20, 2021.

(b) AFFECTED ADS

    None.

(c) APPLICABILITY

    This AD applies to Gulfstream Aerospace Corporation Model GV and GV-SP
    airplanes, all serial numbers, certificated in any category.

Note 1 to paragraph (c): Model GV-SP airplanes are also referred to by the
marketing designations G500, G550, and G500-5000.

(d) SUBJECT

    Joint Aircraft System Component (JASC) Code 5510 Horizontal Stabilizer
    Structure.

(e) UNSAFE CONDITION

    This  AD results  from corrosion  of the  horizontal stabilizer  lower
    bonded  skin assemblies.  The FAA  is issuing  this AD  to detect  and
    correct bond line corrosion, which  if not addressed, could result  in
    compromise of  the structural  integrity of  the horizontal stabilizer
    and lead to loss of control of the airplane.

(f) COMPLIANCE

    Comply  with this  AD within  the compliance  times specified,  unless
    already done.

(g) INCORPORATION OF AIRWORTHINESS LIMITATIONS (ALS) REVISIONS

    Within 30 days after the  effective date of this AD,  incorporate into
    your  existing  maintenance  or inspection  program  the  ALS revision
    specified  in  paragraph (g)(1),  (2),  or (3)  of  this AD  for  your
    applicable airplane designation.

(1) For Model GV airplanes: Section F and Table 12:  Horizontal Stabilizer
    Inspection Table in section 05-10-10,  Airworthiness  Limitations,  of
    the Gulfstream V Maintenance Manual, dated February 28, 2020;

(2) For  Model GV-SP (G500 and G500-5000)  airplanes:  Section F and Table
    12: Horizontal Stabilizer Inspection Table  in section 05-10-10,  Air-
    worthiness Limitations, of the Gulfstream G500-5000 Maintenance Manual
    dated March 15, 2021; or

(3) For Model GV-SP (G550) airplanes:  Section F and Table 12:  Horizontal
    Stabilizer Inspection Table in section 05-10-10, Airworthiness Limita-
    tions, of the Gulfstream G550 Maintenance Manual dated March 15, 2021.

(h) APPLICABLE CUSTOMER BULLETINS

    The customer bulletins specified  in paragraphs (h)(1) through  (3) of
    this AD contain procedures for compliance with the actions required by
    paragraph (i) of this AD for your applicable airplane designation.

(1) Gulfstream GV Customer Bulletin No. 228, Revision B, dated October 31,
    2019;

(2) Gulfstream  G500-5000  Customer Bulletin  No. 190,  Revision B,  dated
    October 31, 2019; or

(3) Gulfstream G550 Customer Bulletin No. 190, Revision B,  dated  October
    31, 2019.

(i) INSPECTION

    For Model GV airplanes, all serial numbers, and Model GV-SP airplanes,
    serial numbers  5001 through  5158, where  more than  132 months  have
    elapsed since  the original  certificate of  airworthiness issue  date
    (often referred to  as entry into  service date), as  of the effective
    date of this AD: Within 12 months after the effective date of this AD,
    perform  the  horizontal   stabilizer  lower  skin   resonance  C-Scan
    inspection  (Part II  inspection) for  bond line  corrosion and  apply
    corrosion inhibiting compound (CIC) by following steps 6.2.a.  through
    6.2.e. and 6.3.a.  of appendix A  of the applicable  customer bulletin
    listed in paragraph (h) of this AD.

Note 2 to the introductory text of paragraph (i):  The  inspections listed
in the applicable ALS  revision in paragraph (g)  of this AD must  also be
accomplished at the same time you perform the Part II inspection.

(1) Within 48 months  after applying CIC,  repair the area  using a method
    approved as specified in paragraph (j)(3) of this AD.

(2) If there is bond line corrosion  that  exceeds  the  allowable  damage
    limit, before further flight,  repair the area using a method approved
    as specified in paragraph (j)(3) of this AD.

(j) ALTERNATIVE METHODS OF COMPLIANCE (AMOCS)

(1) The  Manager,  Atlanta ACO Branch,  FAA,  has the authority to approve
    AMOCs for this AD, if requested  using the procedures found in 14  CFR
    39.19. In  accordance with  14 CFR  39.19, send  your request  to your
    principal  inspector  or  local Flight  Standards District  Office, as
    appropriate. If  sending information  directly to  the manager  of the
    certification  office,  send  it  to  the  attention  of  the   person
    identified in paragraph (k)(1) of this AD.

(2) Before using any approved AMOC,  notify your appropriate principal in-
    spector, or lacking  a principal inspector,  the manager of  the local
    flight standards district office/certificate holding district office.

(3) An AMOC that provides an acceptable level of safety may  be  used  for
    any repair, modification, or alteration  required by this AD if  it is
    approved by a  Gulfstream Engineering Authorized  Representative (EAR)
    of the Gulfstream  Organization Designation Authorization  (ODA), that
    has been authorized by the Manager, Atlanta ACO Branch, to make  those
    findings.  To  be  approved, the  repair,  modification  deviation, or
    alteration  deviation  must  meet  the  certification  basis  of   the
    airplane, and the approval must specifically refer to this AD.

(4) For service information  that  contains  steps  that  are  labeled  as
    Required for Compliance (RC), the following provisions apply.

(i) The steps labeled as RC,  including substeps under  an RC step and any
    figures identified in an RC step,  must be done to comply with the AD.
    An AMOC is required for any deviations to RC steps, including substeps
    and identified figures.

(ii) Steps not labeled as RC  may be deviated  from using accepted methods
     in accordance with the  operatorís maintenance or inspection  program
     without  obtaining  approval  of  an  AMOC,  provided  the  RC steps,
     including  substeps  and identified  figures,  can still  be  done as
     specified,  and  the  airplane  can  be  put  back  in  an  airworthy
     condition.

(k) RELATED INFORMATION

(1) For more information about this AD,  contact Ronald Wissing,  Aviation
    Safety Engineer,  Atlanta  ACO  Branch,  FAA,  1701  Columbia  Avenue,
    College Park, GA  30337;  phone: (404) 474-5552;  fax: (404) 474-5606;
    email: ronald.wissing@faa.gov.

(2) For service information identified  in  this  AD,  contact  Gulfstream
    Aerospace Corporation,  Technical Publications  Dept., P.O.  Box 2206,
    Savannah, GA 31402; phone: (800) 810-4853; fax: (912) 965-3520; email:
    pubs@gulfstream.com;  website:  https://www.gulfstream.com/en/customer
    -support/. You  may view  this referenced  service information  at the
    FAA, Airworthiness  Products Section,  Operational Safety  Branch, 901
    Locust, Kansas City, MO 64106. For information on the availability  of
    this material at the FAA, call (816) 329-4148.

Issued on October 28, 2021. Lance T Gant, Director, Compliance & Airworth-
iness Division, Aircraft Certification Service.

DATES: The FAA must receive comments  on this proposed AD  by December 20,
2021.
PREAMBLE 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0958; Project Identifier 2019-CE-010-AD]
RIN 2120-AA64

Airworthiness Directives; Gulfstream Aerospace Corporation
Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for all Gulfstream Aerospace Corporation (Gulfstream) Model GV and GV-
SP airplanes. This proposed AD results from corrosion of the horizontal
stabilizer lower bonded skin assemblies. This proposed AD would require
inspecting the horizontal stabilizer lower skin and associated bonded
doublers and bonded stringers, repairing the area susceptible to
corrosion, and incorporating revisions to the airworthiness limitations
section (ALS) in the existing aircraft maintenance manual (AMM). The
FAA is proposing this AD to address the unsafe condition on these
products.

DATES: The FAA must receive comments on this proposed AD by December
20, 2021.

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 https://www.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.
For service information identified in this NPRM, contact Gulfstream
Aerospace Corporation, Technical Publications Dept., P.O. Box 2206,
Savannah, GA 31402; phone: (800) 810-4853; fax: (912) 965-3520; email:
pubs@gulfstream.com; website: https://www.gulfstream.com/en/customer-support/.
You may view this service information at the FAA,
Airworthiness Products Section, Operational Safety Branch, 901 Locust,
Kansas City, MO 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 at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0958; 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 NPRM, any comments
received, and other information. The street address for Docket
Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Ronald Wissing, Aviation Safety
Engineer, Atlanta ACO Branch, FAA, 1701 Columbia Avenue, College Park,
GA 30337; phone: (404) 474-5552; fax: (404) 474-5606; email:
ronald.wissing@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under ADDRESSES. Include ``Docket No. FAA-2021-0958; Project Identifier
2019-CE-010-AD'' at the beginning of your comments. The most helpful
comments reference a specific portion of the proposal, 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 proposal 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
https://www.regulations.gov, including any personal information you
provide. The agency will also post a report summarizing each
substantive verbal contact received about this NPRM.

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 NPRM 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 NPRM, 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 NPRM. Submissions containing CBI should be sent to
Ronald Wissing, Aviation Safety Engineer, Atlanta ACO Branch, FAA, 1701
Columbia Avenue, College Park, GA 30337. Any commentary that the FAA
receives which is not specifically designated as CBI will be placed in
the public docket for this rulemaking.

Background

Gulfstream notified the FAA of bond line corrosion on Model GV and
GV-SP airplanes, which causes disbonding between the horizontal
stabilizer lower skin and associated bonded doublers and bonded
stringers. Gulfstream determined that the existing visual inspection in
the AMM does not reliably detect bond line corrosion, and they added a
repetitive non-destructive testing (NDT) inspection to detect the
damage. Gulfstream added the revised inspections to the ALS of the AMM.
This condition, if not addressed, could compromise the structural
integrity of the horizontal stabilizer and lead to loss of control of
the airplane.

FAA's Determination

The FAA is issuing this NPRM after determining that the unsafe
condition described previously is likely to exist or develop on other
products of the same type design.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Gulfstream G500-5000 Customer Bulletin No. 190,
Revision B; Gulfstream G550 Customer Bulletin No. 190, Revision B; and
Gulfstream GV Customer Bulletin No. 228, Revision B; all dated October
31, 2019. For the applicable marketing designation specified on each
document, the customer bulletins specify procedures for inspecting the
horizontal stabilizer lower bonded skin.
The FAA also reviewed Gulfstream V Maintenance Manual,
Airworthiness Limitations, Section 05-10-10, dated February 28, 2020;
Gulfstream G500-5000 Maintenance Manual, Airworthiness Limitations,
Section 05-10-10, dated March 15, 2021; and Gulfstream G550 Maintenance
Manual, Airworthiness Limitations, Section 05-10-10, dated March 15,
2021. For the applicable marketing designation specified on each
document, the service information contains inspection intervals for
nondestructive testing of the lower horizontal stabilizer skins and
provides the specific reference for the inspection procedures.

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 ADDRESSES.

Other Related Service Information

The FAA also reviewed the following service documents related to
this NPRM:
Gulfstream Service Letter Document No. GSL505510019,
Revision E, dated September 3, 2021, which contains procedures for
applying on-wing corrosion inhibiting compound to the horizontal
stabilizer.
Gulfstream Service Letter Document No. GSL505510020,
Revision C, dated March 12, 2020, which contains procedures for
applying corrosion inhibiting compound to the horizontal stabilizer.
Gulfstream V Nondestructive Testing Procedures Manual
Chapter 05-00-00, 1. Horizontal Stabilizer Lower Skin Resonance C-
Scan--NDT Procedure.

Proposed AD Requirements in This NPRM

This proposed AD would require inspecting the horizontal stabilizer
lower skin and associated bonded doublers and bonded stringers,
repairing the area susceptible to corrosion, and incorporating
revisions to the ALS of the existing AMM.

Differences Between This Proposed AD and the Service Information

The differences between Gulfstream G500-5000 Customer Bulletin No.
190, Revision B; Gulfstream G550 Customer Bulletin No. 190, Revision B;
and Gulfstream V Customer Bulletin No. 228, Revision B; all dated
October 31, 2019, and this proposed AD are listed below.
The service bulletins exclude certain serial-numbered
airplanes inspected by Gulfstream, but this proposed AD would apply to
all Model GV and GV-SP airplanes.
The service bulletins include an optional horizontal
stabilizer lower skin resonance A-Scan NDT inspection (referred to in
the Customer Bulletin as ``Part I Inspection'') for critical areas of
the horizontal stabilizer bonded lower skin assemblies, but this
proposed AD would not require the Part I Inspection.
The service bulletins allow the horizontal stabilizer
lower skin resonance C-Scan NDT inspection (referred to in the Customer
Bulletin as a ``Part II Inspection'') and application of corrosion
inhibiting compound to be repeated indefinitely every 48 months. This
proposed AD would only allow the Part II inspection to be performed one
time and, within 48 months after the inspection, would require approved
repairs.
The customer bulletins contain actions labeled ``Required
for Compliance'' (RC), and the language in the customer bulletin and in
paragraph (j)(4) of this proposed AD indicate that operators must
comply with all actions labeled RC for compliance with this AD.
However, this AD does not require all of the steps in the customer
bulletins that are labeled as RC. Operators only need to comply with
the RC steps required by paragraph (i) of this AD.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect up to 694 airplanes of U.S. registry. The FAA estimates the
following costs to comply with this proposed AD:

Estimated Costs

Action Labor cost Parts cost Cost per product Cost on U.S. operators
Resonance C-Scan NDT (Part II) inspection and CIC application 80 work-hours x $85 per hour = $6,800 Not applicable $6,800 $2,196,400 (for 323 airplanes)
AMM revision 1 work-hour x $85 per hour = $85 Not applicable 85 $58,990 (for 694 airplanes)

The extent of corrosion found during the proposed inspection may
vary significantly from airplane to airplane. The FAA has no way of
determining the number of airplanes that might need repair or the cost
to repair each airplane.

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

The FAA determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would 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 this proposed
regulation:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Would not affect intrastate aviation in Alaska, and
(3) Would 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
reference, Safety.

The Proposed Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 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: