E7-14433. Airworthiness Directives; Thrush Aircraft, Inc. Models S2R Series Airplanes

AGENCY:

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

ACTION:

Notice of proposed rulemaking (NPRM).

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: [phone].
• 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: [phone]; 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: [phone]; facsimile: [phone]; e-mail: [e-mail]; or

—Mike Cann, Aerospace Engineer, ACE-117A, Atlanta Aircraft Certification Office, One Crown Center, 1895 Phoenix Blvd., Suite 450, Atlanta, Georgia 30349; telephone: [phone]; facsimile: [phone]; e-mail: [e-mail].

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 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:

Labor cost	Parts cost	Total cost per airplane	Total cost on U.S. operators
8 work-hours × $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:

Labor cost	Parts cost	Total cost per airplane
12 work-hours × $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:

Labor cost	Parts cost	Total cost per airplane	Total cost on U.S. operators
30 work-hours × $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.

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 [phone]) 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.

§ 39.13

[Amended]

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

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: [phone]; facsimile: [phone]; e-mail: [e-mail]; or Mike Cann, Aerospace Engineer, ACE-117A, Atlanta Aircraft Certification Office, One Crown Center, 1895 Phoenix Blvd., Suite 450, Atlanta, Georgia 30349; telephone: [phone]; facsimile: [phone]; e-mail: [e-mail]. 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: [phone]; 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.