E7-16103. Airworthiness Directives; Boeing Model 757-200, -200CB, and -300 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 certain Boeing Model 757-200, -200CB, and -300 series airplanes. This proposed AD would require repetitive inspections for cracks of the intercostal tee clips and attachment fasteners at the number 3 and number 4 doorstops of the passenger door cutouts, or repetitive inspections for cracks of the intercostal tee clips; and related investigative/ corrective actions if necessary. This proposed AD also provides an optional terminating action for the repetitive inspections. This proposed AD results from reports of cracked intercostal tee clips at the number 3 and number 4 doorstops of the passenger door cutouts. We are proposing this AD to detect and correct cracking of the tee clips, which could result in additional stress on the adjacent tee clips, surrounding intercostals, edge frame, door structure and doorstops. This additional stress could cause further cracking or breaking of the tee clips, which could result in failure of the door to seal and consequent rapid decompression of the airplane.

DATES:

We must receive comments on this proposed AD by October 1, 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:

Dennis Stremick, 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

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-2007-28990; Directorate Identifier 2007-NM-033-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 eight reports indicating that cracked intercostal tee clips were found at the number 3 and number 4 doorstops of the passenger door cutouts on certain Boeing Model 757-200, -200CB, and -300 series airplanes. These cracks were found during normal maintenance checks on passenger doorway number 4, at the aft edge frame of body station 1681.8 on the left and right sides. On two airplanes, cracks were found on the intercostal tee clips at both the number 3 and number 4 doorstops. The cracks occurred in the radius area of the tee clip, between the horizontal and vertical flange. The number of flight cycles for these airplanes was between 22,700 and 25,000. The cracks in the tee clips are attributed to a preload of the tee clip; continued flight with cracks in the tee clips can place additional stress on the adjacent tee clips, surrounding intercostals, edge frame, door structure and doorstops. This additional stress, if not corrected, could cause further cracking or breaking of the tee clips, which could result in failure of the door to seal and consequent rapid decompression of the airplane.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 757-53A0093, dated November 8, 2006. The service bulletin describes procedures for repetitive detailed inspections with a borescope for cracks of the intercostal tee clips; or repetitive detailed inspections for cracks of the intercostal tee clips and attachment fasteners at the number 3 and number 4 doorstops of the passenger door cutouts after the galley/lavatory has been removed; and related investigative and corrective actions if necessary. The related investigative and corrective actions include the following:

• Condition 1: For airplanes on which any tee clip for only door stop intercostal number 3 is cracked or broken; the procedures specify replacing any cracked tee clip with a new tee clip and contacting Boeing before further flight. In addition, the procedures describe inspections of the door stop fittings on the forward side of body station 1681.8 edge frame; the inner chord, web, and outer chord; the number 4 door structure including the door stop fittings and stop beams above and below the cracked tee clips; and the number 4 aft door frame.
• Condition 2: For airplanes on which any tee clip for only door stop intercostal number 4 is cracked or broken; the procedures specify replacing any cracked tee clip with a new tee clip and contacting Boeing before further flight. In addition, the procedures describe inspections of the tee clip and intercostal for cracking at door stop intercostal number 5; and from door stop number 3 through number 5: Inspecting the door stop fittings on the forward side of the body station 1681.8 edge frame; the inner chord, web, and outer chord; the number 4 door structure including the door stop fittings and stop beams above and below the cracked tee clips; and the number 4 aft door frame.
• Condition 3: For airplanes on which both tee clips for only door stop intercostal numbers 3 and 4 are cracked or broken; the procedures specify replacing the cracked tee clip with a new tee clip and contacting Boeing before further flight. In addition, the procedures describe inspections of the fasteners; the door stop fittings on the forward side of the body station 1681.8 edge frame; the inner chord, web, and outer chord; the number 4 door structure including the door stop fittings and stop beams above and below the cracked tee clips; for airplanes with greater than 28,000 flight cycles, the fasteners and the fillet radius of the stop fittings; and the number 4 aft door frame.

If cracked or broken tee clips are found during any inspection, the procedures describe inspecting the tee clip and intercostal for cracks of the door stop intercostal number 2 and doing inspections from door stop numbers 2 through 5. The additional inspections are for cracks of the door stop fittings; the inner chord, web, and outer chord; and the body station 1681.8 edge frame.

Replacing both tee clips on the left and right sides with new tee clips would eliminate the need for the repetitive inspections. 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 “Difference Between the Proposed AD and Service Information.”

Difference Between the Proposed AD and Service Information

The service bulletin specifies to contact the manufacturer 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.

Costs of Compliance

There are about 912 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 324 airplanes of U.S. registry.

The proposed detailed inspection, if accomplished, would take about 2 work hours per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the inspections proposed by this AD is $51,840, or $160 per airplane, per inspection cycle.

The proposed borescope inspection, if accomplished, would take about 3 work hours per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the inspections proposed by this AD is $77,760, or $240 per airplane, per inspection cycle.

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-2007-28990; Directorate Identifier 2007-NM-033-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by October 1, 2007.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 757-200, -200CB, and -300 series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin 757-53A0093, dated November 8, 2006.

Unsafe Condition

(d) This AD results from reports of cracked intercostal tee clips at the number 3 and number 4 doorstops of the passenger door cutouts. We are issuing this AD to detect and correct cracking of the tee clips, which could result in additional stress on the adjacent tee clips, surrounding intercostals, edge frame, door structure and doorstops. This additional stress could cause further cracking or breaking of the tee clips, which could result in failure of the door to seal and consequent rapid decompression 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.

Repetitive Inspections/Investigative and Corrective Actions

(f) Before the accumulation of 20,000 total flight cycles or within 3,000 flight cycles after the effective date of this AD, whichever is later: Do the applicable inspection specified in paragraph (f)(1) or (f)(2) of this AD by doing all the actions including all applicable related investigative (additional detailed inspections if necessary) and corrective actions; except as provided by paragraph (g) of this AD; in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 757-53A0093, dated November 8, 2006. All related investigative and corrective actions must be done before further flight.

(1) Do a detailed inspection for cracks of the intercostal tee clips and attachment fasteners at the number 3 and number 4 doorstops of the passenger door cutouts. Repeat the inspection thereafter at intervals not to exceed 3,000 flight cycles until accomplishment of the terminating action specified in paragraph (h) of this AD.

(2) Do a detailed inspection with a borescope for cracks of the intercostal tee clips. Repeat the inspection thereafter at intervals not to exceed 3,000 flight cycles until accomplishment of the terminating action specified in paragraph (h) of this AD.

(g) If any cracked structure is found during any inspection required by this AD, and the Accomplishment Instructions of Boeing Alert Service Bulletin 757-53A0093, dated November 8, 2006, specify to contact Boeing for appropriate action: Before further flight, repair any cracked structure using a method approved in accordance with the procedures specified in paragraph (i)(2) of this AD.

Optional Terminating Action

(h) Replacing both intercostal tee clips on the left and right sides with new tee clips in accordance with Part 3 of the Accomplishment Instructions of Boeing Alert Service Bulletin 757-53A0093, dated November 8, 2006, terminates the repetitive inspections required by this AD.

Alternative Methods of Compliance (AMOCs)

(i)(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) 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.

(3) 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.

Issued in Renton, Washington, on August 2, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.