E7-14638. Airworthiness Directives; Boeing Model 707 Airplanes and Model 720 and 720B Series Airplanes

AGENCY:

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

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for all Boeing Model 707 airplanes and Model 720 and 720B series airplanes. This proposed AD would require identifying the material used in the elevator hinge support fittings of the horizontal stabilizer trailing edge, doing repetitive detailed inspections for cracking of the fittings and corrective actions if necessary, and doing an eventual terminating action. This proposed AD results from a report that stress corrosion cracking of the elevator hinge support fittings has been discovered on several Model 707 airplanes. We are proposing this AD to prevent cracking of the elevator hinge support fittings, which could reduce the elevator support stiffness and lead to in-flight airframe vibration, consequent damage to the elevator and horizontal stabilizer, and reduced controllability of the airplane.

DATES:

We must receive comments on this proposed AD by September 13, 2007.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD.

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking Web site: Go to http://www.regulations.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: Room W12-140 on the ground floor of the West Building, 1200 New Jersey Avenue, SE., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for the service information identified in this proposed AD.

FOR FURTHER INFORMATION CONTACT:

Duong Tran, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed in the ADDRESSES section. Include the docket number “FAA-2007-28811; Directorate Identifier 2006-NM-246-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 with FAA personnel concerning this proposed AD. Using the search function of that Web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may visit http://dms.dot.gov.

Examining the Docket

You may examine the AD docket on the Internet at http://dms.dot.gov,, or in person at the Docket Operations office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Operations office (telephone [phone]) is located on the ground floor of the West Building at the DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the Docket Management System receives them.

Discussion

We have received a report indicating that stress corrosion cracking of the elevator hinge support fittings (made of 7079-T6 material) of the horizontal stabilizer trailing edge has been discovered on several Model 707 airplanes. In some cases, multiple fittings on one stabilizer were found to be cracked; excessive cracking at multiple rib locations will reduce the elevator support stiffness. This condition, if not corrected, could lead to in-flight airframe vibration, consequent damage to the elevator and horizontal stabilizer, and reduced controllability of the airplane.

Relevant Service Information

We have reviewed Boeing 707 Alert Service Bulletin A3518, dated October 9, 2006. The alert service bulletin describes procedures for:

• Repetitively verifying whether or not the elevator hinge support fittings of the horizontal stabilizer trailing edge are made of 7079-T6 or 7075-T6 material;
• Modifying certain rib web segments by fabricating and installing nutplates to create access to the web area for inspection;
• Doing initial and repetitive inspections for cracking of hinge support fittings made of 7079-T6 or 7075-T6 material, and corrective actions if necessary; and
• Eventually replacing all affected hinge support fittings with new, improved fittings made of 7075-T7351 material.

Corrective actions include repairing or replacing any cracked fitting with a new or serviceable fitting made of 7079-T6 or 7075-T6 material, or with a new, improved fitting. Replacing any affected fitting with a new, improved fitting made of 7075-T7351 material eliminates the need for the repetitive inspections for that fitting. Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other airplanes of this same type design. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously, except as discussed under “Differences Between the Proposed AD and Service Bulletin.”

Differences Between the Proposed AD and Service Bulletin

The alert service bulletin specifies to contact Boeing for instructions on how to repair certain conditions, but this proposed AD would require repairing those conditions in one of the following ways:

• Using a method that we approve; or
• Using data that meet the certification basis of the airplane, and that have been approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization whom we have authorized to make those findings.

The alert service bulletin does not specify a number of work hours for modifying the rib web segments. However, we have confirmed with Boeing that this action should take about 6 work hours and have estimated the costs to accomplish this proposed AD accordingly.

The alert service bulletin specifies to repeat the verification of the hinge material at intervals not to exceed 180 days after the date on the alert service bulletin or before further flight after the replacement of any hinge support fitting, whichever occurs first. We have confirmed with Boeing that repetitive verification at intervals not to exceed 180 days is not necessary. Therefore, this proposed AD would only require repeat verification of the hinge material before further flight after the replacement of any hinge support fitting.

Costs of Compliance

There are about 185 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 52 airplanes of U.S. registry. The following table provides the estimated costs for U.S. operators to comply with this proposed AD, at an average labor rate of $80 per work hour.

Estimated Costs

Action	Work hours	Parts	Cost per airplane	Fleet cost
Material verification	1	No parts needed	$80	$4,160.
Detailed inspections	24, per inspection cycle	No parts needed	$1,920	$47,840, per inspection cycle.
Modification (fabrication and installation of nutplates)	6	Operator supplied	$480	$24,960.
Terminating action	132	$53,078 1 or $87,750 2	$63,638 1 or $98,310 2	Up to $5,112,120.
1 For Group 1 airplanes.
2 For Group 2 airplanes.

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. 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, 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 Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-28811; Directorate Identifier 2006-NM-246-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by September 13, 2007.

Affected ADs

(b) None.

Applicability

(c) This AD applies to all Model 707-100 long body, -200, -100B long body, and -100B short body series airplanes; Model 707-300, -300B, -300C, and -400 series airplanes; and Model 720 and 720B series airplanes; certificated in any category.

Unsafe Condition

(d) This AD results from a report that stress corrosion cracking of the elevator hinge support fittings of the horizontal stabilizer trailing edge has been discovered on several Model 707 airplanes. We are issuing this AD to prevent cracking of the elevator hinge support fittings, which could reduce the elevator support stiffness and lead to in-flight airframe vibration, consequent damage to the elevator and horizontal stabilizer, and reduced controllability of the airplane.

Compliance

(e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.

Service Bulletin Reference

(f) The term “service bulletin,” as used in this AD, means the Accomplishment Instructions of Boeing 707 Alert Service Bulletin A3518, dated October 9, 2006.

Material Identification

(g) Within 180 days after the effective date of this AD or before further flight after any horizontal stabilizer is replaced: Verify the type of material used in the elevator hinge support fittings of the horizontal stabilizer trailing edge, in accordance with Part 1 of the Accomplishment Instructions of the service bulletin, then do the requirements of paragraph (g)(1) or (g)(2) of this AD, as applicable. Repeat the verification before further flight after the replacement of any hinge support fitting.

(1) For any hinge support fitting made of 7075-T7351 material: No further action is required by paragraph (h) or (i) of this AD.

(2) For any hinge support fitting made of 7079-T6 or 7075-T6 material: Do the actions required by paragraph (h) of this AD.

Repetitive Inspections, One-Time Modification, and Corrective Actions

(h) Before further flight after doing paragraph (g) of this AD, do a detailed inspection for cracking of the hinge support fittings and modify certain segments of the rib webs, in accordance with Part 2 of the Accomplishment Instructions of the service bulletin. For any hinge support fitting found to be cracked or damaged, before further flight, do the actions of paragraph (h)(1) or (h)(2) of this AD; in accordance with Part 3 of the Accomplishment Instructions of the service bulletin. Do all actions in accordance with the Accomplishment Instructions of the service bulletin; except where the service bulletin specifies to contact the manufacturer for repair procedures, this AD requires repair using a method approved in accordance with the procedures specified in paragraph (k) of this AD.

(1) Replace the fitting with a serviceable fitting made of 7079-T6 or 7075-T6 material. Repeat the detailed inspection thereafter at intervals not to exceed 180 days, until the terminating action of paragraph (i) of this AD has been done.

(2) Replace the fitting with a new, improved fitting made of 7075-T7351 material.

Terminating Action

(i) For all airplanes: Within 48 months after the effective date of this AD, replace all hinge support fittings made of 7079-T6 or 7075-T6 material with new, improved fittings made of 7075-T7351 material, in accordance with Part 4 of the Accomplishment Instructions of the service bulletin. Doing this action terminates all requirements of paragraphs (g) and (h) of this AD.

Parts Installation

(j) As of the effective date of this AD, no person may install, on any airplane, a new or serviceable hinge support fitting made of 7079-T6 or 7075-T6 material, unless the requirements of paragraph (h)(1) of this AD are accomplished.

Alternative Methods of Compliance (AMOCs)

(k)(1) The Manager, Seattle Aircraft Certification Office (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) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. 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.

(3) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD, if it is approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization who has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the repair must meet the certification basis of the airplane and the approval must specifically refer to this AD.

Issued in Renton, Washington, on July 18, 2007.

Stephen P. Boyd,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.