Airworthiness Directives; Gulfstream Aerospace Corporation Model G-159 Airplanes, 14123-14126 [E6-4050]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 71, Number 54 (Tuesday, March 21, 2006)]
[Proposed Rules]
[Pages 14123-14126]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E6-4050]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-143-AD]
RIN 2120-AA64


Airworthiness Directives; Gulfstream Aerospace Corporation Model 
G-159 Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Supplemental notice of proposed rulemaking; reopening of 
comment period.

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SUMMARY: The FAA is revising an earlier proposed airworthiness 
directive (AD), applicable to all Gulfstream Aerospace Corporation 
Model G-159 airplanes. The original NPRM would have required repetitive 
non-destructive testing inspections to detect corrosion of the skin of 
certain structural assemblies, and corrective action if necessary. The 
original NPRM also would have required x-ray and ultrasonic inspections 
to detect corrosion and cracking of the splicing of certain structural 
assemblies, and repair if necessary. The original NPRM resulted from 
reports that exfoliation corrosion had been found in the lower layer of 
the lower wing plank splices. This action revises the original NPRM by 
expanding the inspection areas to include the wing lower plank splices, 
ailerons, flaps, elevators, vertical and horizontal stabilizers, 
rudder, rudder trim tab, and aft lower fuselage from fuselage station 
(FS)559 to FS669. The actions specified by this new proposed AD are 
intended to detect and correct corrosion and cracking of the lower wing 
plank splices and spot-welded skins of certain structural assemblies, 
which could result in reduced controllability of the airplane. This 
action is intended to address the identified unsafe condition.

DATES: Comments must be received by April 17, 2006.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 96-NM-143-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9 a.m. and 3 p.m., Monday through Friday, except 
Federal holidays. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must 
contain ``Docket No. 96-NM-143-AD'' in the subject line and need not be 
submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 or 2000 or 
ASCII text.
    The service information referenced in the proposed rule may be 
obtained from Gulfstream Aerospace Corporation, P.O. Box 2206, Mail 
Station D-25, Savannah, Georgia 31402. This information may be examined 
at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., 
Renton, Washington; or at the FAA, Atlanta Aircraft Certification 
Office, One Crown Center, 1895 Phoenix Boulevard, suite 450, Atlanta, 
Georgia.

FOR FURTHER INFORMATION CONTACT: Michael Cann, Aerospace Engineer, 
Airframe Branch, ACE-117A, FAA, Atlanta Aircraft Certification Office, 
One Crown Center, 1895 Phoenix Boulevard, suite 450, Atlanta, Georgia 
30349; telephone (770) 703-6038; fax (770) 703-6097.

SUPPLEMENTARY INFORMATION: 

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this action may be changed in 
light of the comments received.
    Submit comments using the following format:
     Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
     For each issue, state what specific change to the proposed 
AD is being requested.
     Include justification (e.g., reasons or data) for each 
request.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 96-NM-143-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 96-NM-143-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    A proposal to amend part 39 of the Federal Aviation Regulations (14 
CFR part 39) to add an airworthiness directive (AD), applicable to all 
Gulfstream Aerospace Corporation Model G-159 airplanes, was published 
as a notice of proposed rulemaking (NPRM) in the Federal Register on 
June 6, 2001 (66 FR 30343). That NPRM would have required repetitive 
non-destructive testing inspections to detect corrosion of the skin of 
certain structural assemblies, and corrective action if necessary. That 
NPRM also would have required x-ray and ultrasonic inspections to 
detect corrosion and cracking of the splicing of certain structural 
assemblies, and repair if necessary. That NPRM was prompted by reports 
that exfoliation corrosion had been found in the lower layer of the 
lower wing plank splices. That condition, if not corrected, could 
result in local instability failures of the wing under certain load 
conditions and result in degradation of wing capability.

Actions Since Issuance of Previous Proposal

    Since the issuance of that NPRM, we have received additional 
reports indicating corrosion in a larger area of the wing than the area 
specified in the original NPRM. This condition, if not corrected, could 
cause cracking and corrosion of the lower wing plank splices and spot-
welded skins of certain structural assemblies, which could result in 
reduced controllability of the airplane.

[[Page 14124]]

Relevant Customer Bulletin

    Gulfstream Aerospace Corporation has issued Gulfstream GI Customer 
Bulletin (CB) 337B, including Appendix A, dated August 17, 2005. The 
procedures in the CB describe non-destructive testing (NDT) inspections 
for corrosion and cracking of spot-welded skins of the elevators, 
aileron, rudder and rudder trim tab, flaps, aft lower fuselage, and 
vertical and horizontal stabilizers. The procedures in the CB also 
describe NDT inspections (e.g., x-ray and ultrasonic) for exfoliation 
corrosion and cracking for wing plank splices from wing station (WS) 40 
to WS 310. Additionally, the procedures in the CB describe performing 
an eddy current or fluorescent penetrant inspection for evaluating any 
prior blending in the riser areas. The procedures in the CB also 
specify that if the blend-out exceeds the repair drawing 
specifications, contact the manufacturer. The procedures in the CB also 
request operators to send a report to the manufacturer specifying 
inspection results. Additionally, Appendix A provides corrosion repair 
schemes for certain structural repair removal thresholds in accordance 
with certain drawing numbers.
    Gulfstream has also issued Gulfstream Tool No. ST905-377, an x-ray 
negative that is used as a chart to define corrosion levels. The tool 
describes specific levels of corrosion and contains criteria for 
determining certain levels of corrosion (``light,'' ``moderate,'' and 
``severe'').

Comments

    We have considered the following comments on the original NPRM.

Requests To Revise the Cost Impact Section

    Two commenters request that the estimate for the Cost Impact 
section of the original NPRM, which was based on 80 work hours, be 
increased to reflect a more realistic cost. One commenter states that 
it has received price quotes from shops that range from $11,000 to 
$19,000 to perform the actions proposed in the original NPRM. The other 
commenter states that it has completed the inspections (excluding the 
x-rays and ultrasonic inspections) proposed in the original NPRM. The 
operator advises that its actual cost for each inspection, not 
including incidental and access costs, was $18,000.
    We agree that the estimated cost impact should be revised. Based on 
the latest information provided by the manufacturer in Gulfstream GI CB 
337B, we estimate that the work hours necessary for the inspections 
proposed in this supplemental NPRM would be between 300 and 450 work 
hours, depending on how many spot-welded skins have been replaced with 
bonded skin panels. We have revised the Cost Impact section to reflect 
the increase of the estimated work hours.

Request To Revise Initial Compliance Time

    One commenter requests that the initial compliance times be 
revised. The commenter requests that the initial compliance time for 
the requirements of paragraph (a) of the original NPRM be changed to 18 
months from the last inspection of Gulfstream GI CB 337 (referenced in 
the original NPRM as the appropriate source of service information) or 
9 months from the effective date of this AD, whichever is later. The 
commenter states that operators who are currently in compliance with 
Gulfstream GI CB 337 would still be required to re-inspect within 9 
months after the effective date of the AD. The commenter advises that 
this would cause unnecessary cost and airplane downtime, since CB 337 
has an 18-month inspection time.
    We do not agree that, in this case, the initial inspections 
required by paragraphs (a) and (c) of this supplemental NPRM can be 
revised for the convenience of the operators. The inspection areas have 
been expanded since the issuance of the original proposed NPRM, which 
referenced the original issuance of Gulfstream GI CB 337, dated 
December 10, 1993, as the appropriate source of service information. 
The expanded inspection areas are specified in Gulfstream GI CB 337B, 
including Appendix A, dated August 17, 2005, which is referenced in 
this supplemental NPRM as the appropriate source of service 
information. Operators who have accomplished the inspections specified 
in earlier revisions of the CB, may request approval of an extension of 
the compliance time in accordance with paragraph (h) of the 
supplemental NPRM. The repetitive inspections remain at intervals not 
to exceed 18 months. No change is necessary to the supplemental NPRM in 
this regard.

Request Not To Expand the Inspection Area

    One commenter requests that we do not expand the inspection area 
unless it can be shown that those expanded areas have been found to 
have corrosion. The commenter advises that it has been informed by the 
manufacturer that a revision to Gulfstream GI CB 337 is going to be 
issued with additional inspection areas of the wing plank. The 
commenter also states that it has not found corrosion in all of the 
areas specified in the original NPRM.
    We do not agree. We have received several reports indicating that 
corrosion has occurred on the inspection areas discussed in this 
supplemental NPRM, including the wing planks. The source of corrosion 
was determined to be spot-welded skins for the flight controls and aft 
lower fuselage. Gulfstream GI CB 337B, as explained previously, 
describes the appropriate areas of inspection. We have determined that 
an unsafe condition exists and that Gulfstream GI CB 337B describes the 
methods of detection of corrosion and cracking, and correction if 
necessary. We have not changed the supplemental NPRM as a result of 
this request.

Request To Provide a Different Inspection Interval

    That same commenter also requests that, if a sampling of airplanes 
indicates corrosion on other areas, those areas of inspection have a 
different inspection interval than the inboard wing.
    We do not agree. The commenter did not provide a suggested 
``different inspection interval'' or any technical justification for 
what a ``different inspection interval'' might be. However, under the 
provisions of paragraph (h) of the supplemental NPRM, we may approve 
requests for adjustments to the inspection interval if data are 
submitted to substantiate that such an adjustment would provide an 
acceptable level of safety. No change to the supplemental NPRM is 
necessary in this regard.

Request To Revise Compliance Times for Repairs

    Two commenters request that the FAA allow more time to address 
repairs to the wing plank splices. The commenters also request that, if 
corrosion is seen on the x-ray, it may also be confirmed by another 
form of NDT, such as ultrasonic inspection. The commenters both point 
out that all the other inspection areas allow for either mild or 
moderate corrosion to be deferred. One of the commenters requests that 
the FAA allow a ``trace'' of corrosion in the wing plank splices to be 
re-inspected in 18 months to see if the suspect area has changed in 
size, shape, or density before any action must be taken. The commenter 
adds that it is a known fact in the x-ray industry that not all 
indications are corrosion, and the commenter quotes an Applied 
Technical Services report: ``In some cases indications similar to those 
observed on the films provided for evaluation of the wing plank splices

[[Page 14125]]

may actually be attributed to conditions other than corrosion.''
    We do not agree. The loading conditions and magnitudes on the wing 
are different from the flight controls and the fuselage. ``Trace'' 
levels of corrosion on the flight controls and fuselage are not as 
critical as on the wing. No change to the supplemental NPRM is 
necessary in this regard.

Request To Extend the Repetitive Inspection Interval

    One commenter requests that the repetitive inspection interval be 
changed from ``at intervals not to exceed 18 months,'' to ``at 
intervals not to exceed 36 months.'' The commenter notes that, although 
the first Gulfstream GI flew in August of 1958, there has never been a 
structural problem with the wing. The commenter also points out that, 
prior to 1994, there wasn't even a requirement to NDT the parts of the 
GI.
    We do not agree with the commenter's request to extend the 
repetitive inspection interval. In developing an appropriate interval, 
we considered the safety implications, the service history of the 
airplane regarding corrosion of the wings, and normal maintenance 
schedules for timely accomplishment of the inspections. In light of 
these items, we have determined that a 18-month interval is 
appropriate. However, paragraph (h) of the supplemental NPRM provides 
affected operators the opportunity to apply for an adjustment of the 
repetitive inspection interval if the operator also presents data that 
justify the adjustment.

Request To Defer Certain Inspections

    One commenter requests that an inspection compliance time of 12 
years be provided for lower wing planks that have been replaced or 
reconditioned. The commenter states that the manufacturer has told the 
commenter that replaced or reconditioned lower wing planks shouldn't 
need to be inspected for 12 years.
    We do agree that the inspection may be deferred for 12 years if the 
lower wing planks have been replaced with new lower wing planks. Since 
there is no actual definition for ``reconditioned'' in this case, we do 
not agree that the inspection may be deferred for 12 years if the lower 
wing planks have been ``reconditioned.'' However, under the provisions 
of paragraph (h) of this supplemental NPRM, operators may request an 
alternative method of compliance (AMOC) if data are submitted to 
substantiate that such an AMOC would provide an acceptable level of 
safety.

Changes to 14 CFR Part 39/Effect on the Proposed AD

    On July 10, 2002, the FAA issued a new version of 14 CFR part 39 
(67 FR 47997, July 22, 2002), which governs the FAA's airworthiness 
directives system. The regulation now includes material that relates to 
altered products, special flight permits, and alternative methods of 
compliance (AMOCs). These changes are reflected in this supplemental 
NPRM.

FAA's Determination and Proposed Requirements of the Supplemental NPRM

    Certain changes discussed above expand the scope of the original 
NPRM; therefore, we have determined that it is necessary to reopen the 
comment period to provide additional opportunity for public comment on 
this supplemental NPRM.

Difference Between the CB and the Proposed AD

    Operators should note that, although the Gulfstream CB does not 
specify certain corrective actions for levels of corrosion, this 
proposed AD would require shortened repetitive intervals for the NDT 
inspections based on certain levels of corrosion, or replacement of the 
corroded component with a serviceable component. Although the CB 
specifies certain one-time inspections, this supplemental NPRM would 
require repetitive inspections, since the nature of the unsafe 
condition (corrosion and cracking) may occur after a one-time 
inspection. This difference has been coordinated with the manufacturer.

Clarification of a Note in the CB

    The Gulfstream CB includes a note in the Accomplishment 
Instructions to contact a Gulfstream Field Service Representative if 
technical assistance is required in accomplishing the CB. We have 
included Note 1 in this proposed AD to clarify that any deviation from 
the instructions provided in the CB must be approved as an alternative 
method of compliance under paragraph (h) of this AD.

Costs of Compliance

    There are approximately 52 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 25 airplanes of U.S. registry 
would be affected by this proposed AD, that it would take approximately 
between 300 and 450 work hours per airplane, depending upon how many 
spot-welded skins have been replaced with bonded skin panels, to 
accomplish the proposed actions, and that the average labor rate is $65 
per work hour. Based on these figures, the cost impact of the proposed 
AD on U.S. operators is estimated to be between $487,500 and $731,250, 
or between $19,500 and $29,250 per airplane.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the proposed requirements of 
this AD action, and that no operator would accomplish those actions in 
the future if this AD were not adopted. The cost impact figures 
discussed in AD rulemaking actions represent only the time necessary to 
perform the specific actions actually required by the AD. These figures 
typically do not include incidental costs, such as the time required to 
gain access and close up, planning time, or time necessitated by other 
administrative actions.

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.
    We are 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

    We have 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 that the proposed 
regulation:
    1. Is not a ``significant regulatory action'' under Executive Order 
12866;
    2. Is not a ``significant rule'' under the 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

[[Page 14126]]

under the criteria of the Regulatory Flexibility Act.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this supplemental NPRM and placed it in the AD docket. See 
the ADDRESSES section for a location to examine the regulatory 
evaluation.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (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. Section 39.13 is amended by adding the following new 
airworthiness directive:

Gulfstream Aerospace Corporation: Docket 96-NM-143-AD.

    Applicability: All Model G-159 airplanes, certificated in any 
category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To detect and correct corrosion and cracking of the spot-welded 
skins of the lower wing plank splices and certain structural 
assemblies, which could result in reduced controllability of the 
airplane, accomplish the following:

    Note 1: A note in the Accomplishment Instructions of the 
Gulfstream customer bulletin instructs operators to contact 
Gulfstream if any difficulty is encountered in accomplishing the 
customer bulletin. However, any deviation from the instructions 
provided in the service bulletin must be approved as an alternative 
method of compliance (AMOC) under paragraph (h) of this AD.

Non-Destructive Testing Inspections of the Fuselage, Empennage, and 
Flight Controls

    (a) Within 9 months after the effective date of this AD, perform 
a non-destructive test (NDT) to detect corrosion of the skins of the 
elevators, ailerons, rudder and rudder trim tab, flaps, aft lower 
fuselage, and vertical and horizontal stabilizers; in accordance 
with Gulfstream GI Customer Bulletin (CB) No. 337B, including 
Appendix A, dated August 17, 2005. The corrosion criteria must be 
determined by the Manager, Atlanta Aircraft Certification Office 
(ACO), FAA. Gulfstream Tool ST905-377 is also an acceptable method 
of determining the corrosion criteria.
    (1) If no corrosion or cracking is detected, repeat the 
inspection thereafter at intervals not to exceed 18 months.
    (2) If all corrosion is detected that meets the criteria of 
``light'' or ``mild'' corrosion, repeat the NDT inspections of that 
component thereafter at intervals not to exceed 12 months.
    (3) If any corrosion is detected that meets the criteria of 
``moderate'' corrosion, repeat the NDT inspection of that component 
thereafter at intervals not to exceed 9 months.
    (4) If any corrosion is detected that meets the criteria of 
``severe'' corrosion, before further flight, replace the component 
with a serviceable component in accordance with the CB.

Existing Repairs

    (b) If any existing repairs are found during the inspections 
required by paragraph (a) of this AD, before further flight, ensure 
that the repairs are in accordance with a method approved by the 
Manager, Atlanta ACO, FAA.

Inspections of the Lower Wing Plank

    (c) Except as provided in paragraph (f) of this AD: Within 9 
months after the effective date of this AD, perform NDT inspections 
to detect corrosion and cracking of the lower wing plank splices in 
accordance with Gulfstream GI CB 337B, including Appendix A, dated 
August 17, 2005.
    (1) If no corrosion or cracking is detected, repeat the NDT 
inspection at intervals not to exceed 18 months.
    (2) If any corrosion or cracking is detected, before further 
flight, perform all applicable investigative actions and corrective 
actions in accordance with the customer bulletin.

Repair Removal Threshold

    (d) For repairs specified in Appendix A of Gulfstream GI CB 
337B, dated August 17, 2005: Within 144 months after the date of the 
repair installation, remove the repaired component and replace it 
with a new or serviceable component, in accordance with Gulfstream 
GI CB 337B, including Appendix A, dated August 17, 2005.

Prior Blending in the Riser Areas

    (e) If, during the performance of the inspections required by 
paragraph (c) or (f) of this AD, the inspection reveals that prior 
blending has been performed on the riser areas: Before further 
flight, perform an eddy current or fluorescent penetrant inspection, 
as applicable, to evaluate the blending, and accomplish appropriate 
corrective actions, in accordance with Gulfstream GI CB 337B, 
including Appendix A, dated August 17, 2005. If any blend-out is 
outside the limits specified in the CB, before further flight, 
repair in a manner approved by the Manager, Atlanta ACO.

For Airplanes With New Lower Wing Planks

    (f) For airplanes with new lower wing planks, as defined by 
paragraphs (f)(1) and (f)(2) of this AD: Within 144 months after 
replacement of the lower wing planks with new lower wing planks, or 
within 9 months after the effective date of this AD, whichever 
occurs later, perform all of the actions, including any other 
related investigative actions and corrective actions, specified in 
paragraph (c) of this AD.

Reporting Requirement

    (g) Within 30 days of performing the inspections required by 
this AD: Submit a report of inspection findings (both positive and 
negative) to Gulfstream Aerospace Corporation; Attention: Technical 
Operations--Mail Station D-10, P. O. Box 2206, Savannah, Georgia 
31402-0080. Information collection requirements contained in this 
regulation have been approved by the Office of Management and Budget 
(OMB) under the provisions of the Paperwork Reduction Act of 1980 
(44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 
2120-0056.

Alternative Methods of Compliance

    (h)(1) The Manager, Atlanta ACO, FAA, has the authority to 
approve AMOCs for this AD, if requested in accordance with the 
procedures found in 14 CFR 39.19.
    (2) Before using any AMOC approved in accordance with Sec.  
39.19 on any airplane to which the AMOC applies, notify the 
appropriate principal inspector in the FAA Flight Standards 
Certificate Holding District Office.

    Issued in Renton, Washington, on March 9, 2006.
Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E6-4050 Filed 3-20-06; 8:45 am]
BILLING CODE 4910-13-P