04-12576. Airworthiness Directives; Boeing Model 707 and 720 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to all Boeing Model 707 and 720 series airplanes, that currently requires inspections of the upper and lower chords of the wing front and rear spars, repair if necessary, and application of corrosion inhibitor to the inspected areas. This action would remove the requirements of the existing AD, require new detailed inspections and new high frequency eddy current (HFEC) inspections for corrosion and cracking, and require certain related follow-on and investigative actions, if necessary. This action also would expand the area of inspection to include the dry bay areas. The actions specified by the proposed AD are intended to find and fix corrosion and stress corrosion cracking of the upper and lower chords on the wing front and rear spars, which could result in reduced structural integrity of the wing. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by July 19, 2004.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2003-NM-06-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 [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. Comments sent via fax or the Internet must contain “Docket No. 2003-NM-06-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 Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Candice Gerretsen, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

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 2003-NM-06-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. 2003-NM-06-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On April 11, 2001, the FAA issued AD 2001-08-02, amendment 39-12179 (66 FR 20383, April 23, 2001), applicable to all Boeing Model 707 and 720 series airplanes, to require inspections of the upper and lower chords of the wing front and rear spars, repair if necessary, and application of corrosion inhibitor to the inspected areas. That action was prompted by a report indicating that a 31-inch crack was found in the radius of the lower chord of the wing front spar in the dry bay area between wing stations 360 and 400. Investigation revealed that 19 inches of the crack were due to stress corrosion, while the remainder was due to ductile separation. The requirements of that AD are intended to find and fix stress corrosion cracking of the upper and lower chords on the wing front and rear spars, which could result in reduced structural integrity of the wing.

Actions Since Issuance of Previous Rule

Since the issuance of that AD, the FAA has received a report indicating that an operator had found a 31-inch crack during a routine inspection six months after it had done the inspection described in Boeing Service Bulletin 3240, Revision 3, dated October 18, 1985 (a referenced source of service information in AD 2001-08-02).

Explanation of Relevant Service Information

We have reviewed and approved Boeing 707 Alert Service Bulletin A3240, Revision 4, dated September 6, 2001. Revision 4 puts more emphasis than Revision 3 on the detailed inspections for corrosion of the upper and lower chords on the front and rear spars, adds a new high frequency eddy current (HFEC) inspection for corrosion and cracking, and expands the area of inspection to include the dry bay areas of the wings. Revision 4 also describes procedures for repair of corrosion and follow-on actions (removing finish, applying a chemical film treatment and primer to certain areas, measuring depth of any removed material, and accomplishing further HFEC inspections, if necessary) for conditions within certain areas or limits. For certain conditions outside the areas or limits specified by Revision 4, the service bulletin specifies that operators contact Boeing for repair. Revision 4 also specifies that operators contact Boeing for any cracking that is found. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

Pertinent requirements of existing ADs are generally restated in a proposed AD. However, due to the complexity of the requirements of AD 2001-08-02 and the fact that some of the requirements of that AD are no longer correct or necessary, we have clarified in Note 1 of this proposed AD that the requirements specified in this proposed AD remove the requirements specified in AD 2001-08-02. We have determined that the actions and compliance times specified in this proposed AD would adequately address the identified unsafe condition in a timely manner.

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require accomplishment of actions specified in Revision 4 of Boeing 707 Alert Service Bulletin A3240, dated September 6, 2001. Except as described below, the actions would be required to be accomplished in accordance with Revision 4.

Difference Between the Service Bulletin and the Proposed AD

Although the service bulletin specifies that operators should contact the manufacturer for certain conditions outside the limits specified in the service bulletin and for disposition of any cracking found, this proposed AD would require operators to repair such conditions or cracking per a method approved by the FAA.

Additionally, where the service bulletin recommends doing the detailed inspections described in Boeing All Base Message M-7200-01-00062 within 30 days after the release of the service bulletin, this proposed AD would require accomplishment of the detailed inspections of the areas per Revision 4 of Boeing 707 Alert Service Bulletin A3240, dated September 6, 2001, within 30 days after the effective date of the AD.

Where the service bulletin specifies applying BMS 3-23 corrosion inhibitor or a Boeing approved equivalent, this proposed AD would require that any application of an equivalent corrosion inhibitor be approved by the FAA.

Change to Labor Rate Estimate

We have reviewed the figures we have used over the past several years to calculate AD costs to operators. To account for various inflationary costs in the airline industry, we find it necessary to increase the labor rate used in these calculations from $60 per work hour to $65 per work hour. The cost impact information, below, reflects this increase in the specified hourly labor rate.

Cost Impact

There are approximately 230 airplanes of the affected design in the worldwide fleet. The FAA estimates that 42 airplanes of U.S. registry would be affected by this proposed AD.

The new actions that are proposed in this AD would not include those actions required by AD 2001-08-02. Therefore, cost impact figures for those actions are not necessary nor provided for in this proposed AD.

The new actions that are proposed in this AD action would take approximately 212 work hours per airplane to accomplish, at an average labor rate of $65 per work hour. Based on these figures, the cost impact of the proposed requirements of this AD on U.S. operators is estimated to be $578,760, or $13,780 per airplane.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the current or 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.

Regulatory Impact

The regulations proposed herein 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. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this 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) if promulgated, 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. A copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

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.

§ 39.13

[Amended]

2. Section 39.13 is amended by removing amendment 39-12179 (66 FR 20383, April 23, 2001), and by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 2003-NM-06-AD. Supersedes AD 2001-08-02, Amendment 39-12179.

Applicability: All Model 707 and 720 series airplanes, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To find and fix corrosion and stress corrosion cracking of the upper and lower spar chords on the front and rear spars of the wing, which could result in reduced structural integrity of the wing, accomplish the following:

Superseding the Requirements of AD 2001-08-02

Note 1:

As of the effective date of this AD, the requirements of AD 2001-08-02, amendment 39-12179, are no longer effective or required.

Definition of Service Bulletin

(a) The term “service bulletin,” as used in this AD, means the Accomplishment Instructions of Boeing 707 Alert Service Bulletin A3240, Revision 4, dated September 6, 2001.

Detailed Inspection

(b) Within 30 days after the effective date of this AD, do a detailed inspection of the entire length of the external surfaces of the front and rear wing spar chords and the internal surfaces of the front spar chords in the dry bays of the wings for corrosion, any signs of corrosion (e.g., blistering or signs of fuel leaks), or cracking; per the Accomplishment Instructions of the service bulletin. If no corrosion or cracking is found, before further flight: Except as specified in paragraph (e) of this AD, accomplish any applicable follow-on actions or investigative actions, per the Accomplishment Instructions of the service bulletin.

Other Repetitive Inspections

(c) Within 6 months after the effective date of this AD, perform a detailed inspection and a high frequency eddy current (HFEC) inspection of the entire length of the external surfaces of the front and rear wing spar chords and the internal surfaces of the front spar chords in the dry bays of the wings for any corrosion, signs of corrosion (e.g., blistering or signs of fuel leaks), or cracking; per the Accomplishment Instructions of the service bulletin. If no corrosion or cracking is found, before further flight, accomplish any applicable follow-on or investigative actions specified in the Accomplishment Instructions of the service bulletin and the actions specified in paragraph (e) of this AD. Thereafter, repeat the detailed and HFEC inspections at intervals not to exceed 12 months.

Repair of Corrosion

(d) If any corrosion or signs of corrosion (e.g., blistering or signs of fuel leaks) are found during any inspection required by this AD: Before further flight, repair per paragraph (d)(1) or (d)(2) of this AD, as applicable.

(1) If the corrosion is within the areas and limits specified in the service bulletin: Except as required by paragraph (e) of this AD, repair and accomplish all applicable follow-on and investigative actions, per the Accomplishment Instructions of the alert service bulletin.

(2) If the corrosion is outside the areas or limits specified in the service bulletin, repair per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or per data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative (DER) who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD.

Application of Corrosion Inhibitor

(e) Where the Accomplishment Instructions of the service bulletin specifies to apply BMS 3-23 (a corrosion inhibitor) or a Boeing approved equivalent, this AD requires that BMS 3-23 must be used or that any application of an equivalent corrosion inhibitor be approved by the Manager, Seattle ACO, or per data meeting the type certification basis of the airplane approved by a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD.

Repair of Cracking

(f) If any cracking is found during any inspection required by this AD, including cracks that have been previously stop-drilled but not permanently repaired: Before further flight, repair per a method approved by the Manager, Seattle ACO; or per data meeting the type certification basis of the airplane approved by a Boeing Company DER who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the approval letter must specifically reference this AD. Operators should note that “stop drilling” of cracks as a means to defer repair is not permitted by this AD.

Alternative Methods of Compliance

(g) In accordance with 14 CFR 39.19, the Manager, Seattle ACO, FAA, is authorized to approve alternative methods of compliance for this AD.

Issued in Renton, Washington, on May 26, 2004.

Kevin M. Mullin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.