[Federal Register Volume 72, Number 143 (Thursday, July 26, 2007)]
[Proposed Rules]
[Pages 41042-41045]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-14433]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-28432; Directorate Identifier 2007-CE-051-AD]
RIN 2120-AA64


Airworthiness Directives; Thrush Aircraft, Inc. Models S2R Series 
Airplanes

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

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to adopt a new airworthiness directive (AD) for 
certain Thrush Aircraft, Inc. (Thrush) Model S2R series airplanes. This 
proposed AD would require repetitive visual inspections of the vertical 
and horizontal stabilizer attach fitting, attach fitting bolts, and the 
vertical fin aft spar for cracks or corrosion and require immediate 
replacement of cracked or corroded parts and eventual replacement if no 
cracks or corrosion is found as terminating action for the repetitive 
inspections. This proposed AD results from reports of cracks in the 
empennage of Thrush S2R series airplanes. We are proposing this AD to 
detect and correct these cracks, which could cause the vertical 
stabilizer to lose structural integrity. This condition could lead to 
loss of control.

DATES: We must receive comments on this proposed AD by September 24, 
2007.

ADDRESSES: Use one of the following addresses to comment on this 
proposed AD:
     DOT Docket Web site: Go to http://dms.dot.gov and follow 
the instructions for sending your comments electronically.
     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.
     Fax: (202) 493-2251.
     Hand Delivery: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.
     Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
    For service information identified in this proposed AD, contact: 
Thrush Aircraft, Inc., P.O. Box 3149, 300 Old Pretoria Road, Albany, 
Georgia 31706-3149; telephone: 229-883-1440; facsimile: 229-436-4856; 
or on the Internet at: http://www.thrushaircraft.com.

FOR FURTHER INFORMATION, CONTACT ONE OF THE FOLLOWING:
--Cindy Lorenzen, Aerospace Engineer, ACE-115A, Atlanta Aircraft 
Certification Office, One Crown Center, 1895 Phoenix Blvd., Suite 450, 
Atlanta, Georgia 30349; telephone: (770) 703-6078; facsimile: (770) 
703-6097; e-mail: [email protected]; or
--Mike Cann, Aerospace Engineer, ACE-117A, Atlanta Aircraft 
Certification Office, One Crown Center, 1895 Phoenix Blvd., Suite 450, 
Atlanta, Georgia 30349; telephone: (770) 703-6038; facsimile: (770) 
703-6097; e-mail: [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments regarding this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include the docket number, ``FAA-
2007-28432; Directorate Identifier 2007-CE-051-AD'' at the beginning of 
your comments. We specifically invite comments on the overall 
regulatory, economic, environmental, and energy aspects of the proposed 
AD. We will consider all comments received by the closing date and may 
amend the proposed AD in light of those comments.
    We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will 
also post a report summarizing each substantive verbal contact we 
receive concerning this proposed AD.

Discussion

    We have received reports of cracks in the empennage of Thrush S2R 
series airplanes. Cracks may occur in the vertical stabilizer attach 
fitting, the horizontal stabilizer attach fitting, attach fitting 
bolts, and/or the vertical fin aft spar on airplanes with metal 
empennages. A metallurgy report suggests stress corrosion cracking is 
the

[[Page 41043]]

cause of these cracks. A report was received from the field that a \5/
16\-inch vertical attach bolt, part number (P/N) NAS1105-68, was found 
broken in two places, causing the rear spar of the vertical fin to 
crack. A separate incident found the attach fitting on the stabilizer 
itself cracked in both lugs from stress corrosion.
    This condition, if not corrected, could cause the vertical 
stabilizer to lose structural integrity. This condition could lead to 
loss of control.

Relevant Service Information

    We have reviewed Thrush Aircraft, Inc., Service Bulletin No. SB-AG-
45, Revision B, dated June 1, 2007. The service information describes 
procedures for inspecting and upgrading the fin spar and attach 
fittings.

FAA's Determination and Requirements of the Proposed AD

    We are proposing this AD because we evaluated all information and 
determined the unsafe condition described previously is likely to exist 
or develop on other products of the same type design. This proposed AD 
would require repetitive visual inspections of the vertical and 
horizontal stabilizer attach fitting, attach fitting bolts, and the 
vertical fin aft spar for cracks or corrosion and require immediate 
replacement of cracked or corroded parts and eventual replacement if no 
cracks or corrosion is found as terminating action for the repetitive 
inspections.

Differences Between This Proposed AD and the Service Information

    Thrush Aircraft, Inc. SB-AG-45, Revision B, dated June 1, 2007, 
recommends an immediate initial inspection. We consider immediately 
upon receipt action to be an urgent safety of flight compliance time. 
Because our risk assessment does not indicate this unsafe condition to 
be an urgent safety of flight condition, we propose to require an 
initial inspection within the next 50 hours time-in-service (TIS). The 
initial inspection time of 50 hours TIS is an adequate compliance for 
this AD action and meets the FAA requirements of an NPRM.
    We propose to require a terminating action of replacing the parts 
within the next 2 years or 2,000 hours TIS, whichever occurs first. 
This is recommended because there is historic evidence that inspections 
alone can eventually miss detecting a crack.

Costs of Compliance

    We estimate that this proposed AD would affect 910 airplanes in the 
U.S. registry.
    We estimate the following costs to do the proposed inspection:

----------------------------------------------------------------------------------------------------------------
                                                                               Total cost per     Total cost on
                 Labor cost                             Parts cost                airplane       U.S. operators
----------------------------------------------------------------------------------------------------------------
8 work-hours x $80 per hour = $640..........  Not applicable................             $640          $582,400
----------------------------------------------------------------------------------------------------------------

    We estimate the following costs to do any necessary replacements of 
the vertical fin aft spar that would be required based on the results 
of the proposed inspection. We have no way of determining the number of 
airplanes that may need this replacement:

------------------------------------------------------------------------
                                                         Total cost per
             Labor cost                  Parts cost         airplane
------------------------------------------------------------------------
12 work-hours x $80 per hour = $960.           $3,800            $4,760
------------------------------------------------------------------------

    We estimate the following costs to replace the vertical and 
horizontal stabilizer attach fittings and attachment bolt:

----------------------------------------------------------------------------------------------------------------
                                                                               Total cost per     Total cost on
                        Labor cost                             Parts cost         airplane       U.S. operators
----------------------------------------------------------------------------------------------------------------
30 work-hours x $80 per hour = $2,400.....................           $1,550            $3,950        $3,594,500
----------------------------------------------------------------------------------------------------------------

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 under the criteria 
of the Regulatory Flexibility Act.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this proposed AD and placed it in the AD docket.

[[Page 41044]]

Examining the AD Docket

    You may examine the AD docket that contains the proposed AD, the 
regulatory evaluation, any comments received, and other information on 
the Internet at http://dms.dot.gov; or in person at the Docket 
Management Facility between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays. The Docket Office (telephone (800) 647-5527) 
is located at the street address stated in the ADDRESSES section. 
Comments will be available in the AD docket shortly after receipt.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, 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 AD:

Thrush Aircraft, Inc.: Docket No. FAA-2007-28432; Directorate 
Identifier 2007-CE-051-AD.

Comments Due Date

    (a) We must receive comments on this airworthiness directive 
(AD) action by September 24, 2007.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to the following airplane models and serial 
numbers that are certificated in any category and are equipped with 
metal empennage part numbers (P/N) 40220 or 95400 (applies to serial 
numbers with or without a ``DC'' suffix):

------------------------------------------------------------------------
               Model                             Serial Nos.
------------------------------------------------------------------------
(1) S2R...........................  1416R through 5100R.
(2) S2R-R1340.....................  R1340-001 through R1340-035.
(3) S2R-R1820.....................  R1820-001 through R1820-036.
(4) S2R-T11.......................  T11-001 through T11-005.
(5) S2R-T15.......................  T15-001 through T15-044 and T27-001
                                     through T27-044.
(6) S2R-T34.......................  6000 through 6049, T34-001 through
                                     T34-279, T36-001 through T36-279,
                                     T41-001 through T41-279, T42-001
                                     through T42-279.
(7) S2RHG-T34.....................  T34HG-101 through T34HG-107.
(8) S2R-T45.......................  T45-001 through T45-015.
(9) S2R-T65.......................  T65-001 through T65-018.
(10) S2RHG-T65....................  T65-001 through T65-018 and T65HG-
                                     011 through T65HG-019.
(11) S2R-G1.......................  G1-101 through G1-115.
(12) S2R-G5.......................  G5-101 through G5-105.
(13) S2R-G6.......................  G6-101 through G6-155.
(14) S2R-G10......................  G10-101 through G10-168.
(15) S2R-T660.....................  T660-101 through T660-120.
------------------------------------------------------------------------

Unsafe Condition

    (d) This proposed AD results from reports of cracks in the 
empennage of Thrush Aircraft, Inc., S2R series airplanes. We are 
proposing this AD to detect and correct these cracks, which could 
cause the vertical stabilizer to lose structural integrity. This 
condition could lead to loss of control.

Compliance

    (e) To address this problem, you must do the following, unless 
already done:

------------------------------------------------------------------------
           Actions                 Compliance            Procedures
------------------------------------------------------------------------
(1) Perform a visual          Within the next 50    Follow Thrush
 inspection of the vertical    hours time-in-        Aircraft, Inc.
 stabilizer attach fitting     service (TIS) after   Service Bulletin
 (P/N 40301-7), the            the effective date    No. SB-AG-45,
 horizontal stabilizer         of this AD and        Revision B, dated
 attach fitting (P/N 40303-1/  repetitively          June 1, 2007.
 -4/-7 or 95267-1),            thereafter at
 attachment bolt (P/N          intervals not to
 NAS1105-68), and vertical     exceed every 100
 fin aft spar (P/N 40261-24    hours TIS for up to
 or P/N 95253-1), for cracks   2 years or a total
 or corrosion.                 of 2,000 hours TIS,
                               whichever occurs
                               first.
(2) If cracks or corrosion    Before further        Follow Thrush
 are found in P/N 40301-7,     flight after any      Aircraft, Inc.
 40303-1/-4/-7, 95267-1, or    inspection where      Service Bulletin
 NAS1105-68 during any         cracks or corrosion   No. SB-AG-45,
 inspection required in        are found.            Revision B, dated
 paragraph (e)(1) of this                            June 1, 2007.
 AD, replace all three parts
 with new P/Ns 95266-3,
 95267-5 and NAS6207-68.
(3) If cracks or corrosion    Before further        Follow Thrush
 are found in P/N 40261-24     flight after any      Aircraft, Inc.
 or 95253-1 during any         inspection where      Service Bulletin
 inspection required in        cracks or corrosion   No. SB-AG-45,
 paragraph (e)(1) of this      are found.            Revision B, dated
 AD, replace with a new P/N                          June 1, 2007.
 40261-24 or 95253-1, or
 repair in accordance with
 Thrush SB-AG-45, Revision B.

[[Page 41045]]

 
(4) Replace vertical          Within the next       Follow Thrush
 stabilizer attach fitting P/  2,000 hours TIS       Aircraft, Inc.
 N 40301-7 with P/N 95266-3,   after the effective   Service Bulletin
 replace horizontal            date of this AD or    No. SB-AG-45,
 stabilizer attach fitting P/  within 2 years        Revision B, dated
 N 40303-1/-4/-7 or 95267-1    after the effective   June 1, 2007.
 with P/N 95267-5, and         date of this AD,
 replace attachment bolt       whichever occurs
 NAS1105-68 with NAS6207-68    first. This action
 bolt.                         terminates the
                               repetitive
                               inspections
                               required in
                               paragraph (e)(1) of
                               this AD, including
                               the inspections of
                               the vertical fin
                               aft spar, P/N 40261-
                               24 or 95253-1.
------------------------------------------------------------------------

Special Flight Permit

    (f) Under 14 CFR part 39.23, we are limiting the special flight 
permits authorized for this AD to ferry aircraft to a maintenance 
facility for inspection by the following conditions:
    (1) Hopper must be empty.
    (2) Vne reduced to 126 m.p.h. (109 knots); and
    (3) No flight into known turbulence.

Alternative Methods of Compliance (AMOCs)

    (g) The Manager, FAA, has the authority to approve AMOCs for 
this AD, if requested using the procedures found in 14 CFR 39.19. 
Send information to ATTN: Cindy Lorenzen, Aerospace Engineer, ACE-
115A, Atlanta Aircraft Certification Office, One Crown Center, 1895 
Phoenix Blvd., Suite 450, Atlanta, GA 30349; telephone: (770) 703-
6078; facsimile: (770) 703-6097; e-mail: [email protected]; or 
Mike Cann, Aerospace Engineer, ACE-117A, Atlanta Aircraft 
Certification Office, One Crown Center, 1895 Phoenix Blvd., Suite 
450, Atlanta, Georgia 30349; telephone: (770) 703-6038; facsimile: 
(770) 703-6097; e-mail: [email protected]. Before using any 
approved AMOC on any airplane to which the AMOC applies, notify your 
appropriate principal inspector (PI) in the FAA Flight Standards 
District Office (FSDO), or lacking a PI, your local FSDO.

Related Information

    (h) To get copies of the service information referenced in this 
AD, contact Thrush Aircraft, Inc., P.O. Box 3149, 300 Old Pretoria 
Road, Albany, Georgia 31706-3149; telephone: 229-883-1440; 
facsimile: 229-436-4856; or on the Internet at: http://www.thrushaircraft.com. To view the AD docket, go to U.S. Department 
of Transportation, Docket Operations, M-30, West Building Ground 
Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 
20590, or on the Internet at http://dms.dot.gov. The docket number 
is Docket No. FAA-2007-28432; Directorate Identifier 2007-CE-051-AD.

    Issued in Kansas City, Missouri, on July 20, 2007.
Kim Smith,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. E7-14433 Filed 7-25-07; 8:45 am]
BILLING CODE 4910-13-P