E8-18812. Airworthiness Directives; Boeing Model 737-100, -200, -200C, -300, -400, and -500 Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final rule.

SUMMARY:

We are adopting a new airworthiness directive (AD) for certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. This AD requires repetitive inspections to detect cracking of the body station 303.9 frame, and corrective action if necessary. This AD also provides for optional terminating action for the repetitive inspections. This AD results from reports of cracks found at the cutout in the web of body station frame 303.9 inboard of stringer 16L. We are issuing this AD to detect and correct such cracking, which could prevent the left forward entry door from sealing correctly, and could cause in-flight decompression of the airplane.

DATES:

This AD is effective September 23, 2008.

The Director of the Federal Register approved the incorporation by reference of certain publications listed in this AD as of September 23, 2008.

ADDRESSES:

For service information identified in this AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

Examining the AD Docket

You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this AD, the regulatory evaluation, any comments received, and other information. The address for the Docket Office (telephone [phone]) is the Document Management Facility, U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT:

Howard Hall, 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:

Discussion

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an airworthiness directive (AD) that would apply to certain Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That NPRM was published in the Federal Register on September 13, 2007 (72 FR 52314). That NPRM proposed to require repetitive inspections to detect cracking of the body station 303.9 frame, and corrective action if necessary. That NPRM also proposed optional terminating action for the repetitive inspections.

Comments

We gave the public the opportunity to participate in developing this AD. We considered the comments received.

Support for the NPRM

Boeing concurs with the NPRM.

Request To Delay Final Rule

The Air Transport Association (ATA), on behalf of its member United Airlines, requests that we delay issuing the final rule until kits (to repair cracks or to terminate the repetitive inspections) are readily available from Boeing. Only Boeing kits are specified; Boeing kit 65C37763-8 is under parts management control by Boeing.

We disagree with the request to delay issuing the final rule. To delay this action would be inappropriate, since we have determined that an unsafe condition exists, and that inspections must be conducted in a timely manner to ensure continued safety. Boeing is aware of the pending AD. We have been advised that kits are currently available from Boeing Spares, and that Boeing has already made forecasts to ensure continued kit availability. Operators that order out-of-stock kits from Boeing can request permission from Boeing Spares to manufacture the kits. We have been advised that Boeing Spares will provide the drawings and specifications required to make kits. The kits related to this AD are made up of simple parts that should be easy for operators to fabricate. We have not changed the final rule regarding this issue.

Request To Allow Existing Repairs as Terminating Action

Continental requests that we revise the NPRM to allow existing FAA-approved repairs (in the inspection area specified in the NPRM) as terminating action for the proposed repetitive inspections. The commenter notes that the service bulletin has no provisions for inspecting existing FAA-approved repairs.

While certain previously installed repairs might be acceptable as a terminating action for the AD inspections, we cannot classify all previously installed repairs—even ones approved by the FAA—as terminating action unless the repair is properly evaluated in light of the requirements of this AD. Paragraph (j) of the final rule provides operators the opportunity to request approval of specific repair configurations as terminating action. Such a request should include data/rationale to show that the repair configuration provides an acceptable level of safety without continued inspections. We have not changed the final rule regarding this issue.

Request To Extend Grace Period

Continental Airlines requests that we revise the NPRM to extend the grace period for the initial inspection (for airplanes that have exceeded the specified flight-cycle threshold). The commenter requests an extension from 2,250 flight cycles to 4,500 flight cycles to coincide with a scheduled heavy maintenance check. The commenter asserts that the proposed grace period would not give operators adequate time to comply with the AD without added financial and logistical burden on the airlines. The commenter refers to AD 2005-20-03, amendment 39-14296 (70 FR 56361, September 27, 2005). That AD also applies to Boeing Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. That AD requires repetitive inspections of the intercostal webs, attachment clips, and stringer splice channels for cracks; and corrective action if necessary. The commenter states that the inspection area is the same for AD 2005-20-03 and the subject NPRM. The grace period for that AD is 4,500 flight cycles, so extending the grace period in the NPRM to 4,500 flight cycles will provide an acceptable safety level in this AD.

We agree with the commenter's request and rationale. We have revised paragraph (h) in this final rule accordingly. We have coordinated this change with Boeing.

Request To Relax Dimensional Tolerances

Continental requests that the dimensional requirements be specified to a maximum of two decimal places with a tolerance of ± 0.03 inch. Figure 11, detail A, of Boeing Alert Service Bulletin 737-53A1188, Revision 2, dated May 9, 2007, specifies enlarging the slotted hole to dimensions of three decimal places. (Boeing Alert Service Bulletin 737-53A1197, dated August 25, 2006, contains similar specifications.) The commenter asserts that a tight (three-decimal-place) tolerance is virtually impossible to attain with this particular modification.

We agree that the noted dimension in the service bulletin is shown to three decimal places. But we disagree that the actual “build to” or “measure to” dimensions must be controlled to three decimal places. According to paragraph 3.A. of the Accomplishment Instructions of the service bulletin, the tolerance for linear dimensions is ± 0.03 inch. Given the two-decimal-place accuracy of this tolerance, the corresponding final dimension will require only two-decimal-place accuracy. So, for example, for a specified dimension of 1.29900 ± 0.03, the final “build to” and “measure to” dimensions, when appropriately rounded to the 2-decimal-place tolerance accuracy, are 1.27-1.33. We have not changed the final rule regarding this issue.

Clarification of Required Service Information

We have revised the final rule to clarify that Revision 2 of Boeing Alert Service Bulletin 737-53A1188 must be used for the requirements of paragraph (f) of this AD.

Conclusion

We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We also determined that these changes will not increase the economic burden on any operator or increase the scope of the AD.

Costs of Compliance

There are about 2,765 airplanes of the affected design in the worldwide fleet. The following table provides the estimated costs, depending on airplane configuration, for U.S. operators to comply with this AD.

Estimated Costs

Action	Work hours	Average labor rate per hour	Parts	Cost per airplane	Number of U.S.- registered airplanes	Fleet cost
Inspection	1 to 4	$80	None	$80 to $320, per inspection cycle	1,154	$92,320 to $369,280, per inspection cycle.
Repair/preventive change, if done	12 to 30	80	$564 to $2,236	$1,524 to $4,636	Up to 1,154	Up to $5,349,944.

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

This AD will not have federalism implications under Executive Order 13132. This AD will 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 this AD:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Is not a “significant rule” under 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.

You can find our regulatory evaluation and the estimated costs of compliance in the AD Docket.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• Safety

Adoption of the Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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:

2008-17-03 Boeing: Amendment 39-15641. Docket No. FAA-2007-29174; Directorate Identifier 2007-NM-125-AD.

Effective Date

(a) This airworthiness directive (AD) is effective September 23, 2008.

Affected ADs

(b) None.

Applicability

(c) This AD applies to the airplanes, certificated in any category, identified in Table 1 of this AD.

Table 1—Applicability

Boeing model—	As identified in Boeing Alert Service Bulletin—
737-100, -200, and -200C series airplanes	737-53A1197, dated August 25, 2006.
737-300, -400, and -500 series airplanes	737-53A1188, Revision 2, dated May 9, 2007, or 737-53A1197, dated August 25, 2006.

Unsafe Condition

(d) This AD results from reports of cracks found at the cutout in the web of body station frame 303.9 inboard of stringer 16L. We are issuing this AD to detect and correct such cracking, which could prevent the left forward entry door from sealing correctly, and could cause in-flight 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: Service Bulletin 737-53A1188

(f) For airplanes identified in Boeing Alert Service Bulletin 737-53A1188, Revision 2, dated May 9, 2007, including airplanes modified by the repair/preventive change specified in the original version, dated April 9, 1998; or Revision 1, dated March 18, 1999; of the service bulletin: Do detailed and high frequency eddy current (HFEC) inspections in the web and doubler around the slotted holes in the frame web at stringers 15L and 16L, in accordance with the Accomplishment Instructions of Revision 2 of the service bulletin. Do the inspections at the applicable time specified in paragraph 1.E. of Revision 2 of the service bulletin, except as provided by paragraph (h) of this AD. Do all applicable corrective actions before further flight in accordance with Revision 2 of the service bulletin, except as provided by paragraph (i) of this AD. Repeat the inspections at intervals not to exceed 4,500 flight cycles until accomplishment of the repair/preventive change in accordance with Revision 2 of the service bulletin, which terminates the repetitive inspection requirements. A repair/preventive change done in accordance with the original version or Revision 1 of the service bulletin does not terminate the repetitive inspections, but the repetitive inspections may be terminated after the existing kit is replaced with a new kit in accordance with paragraph 3.B., Part II, step 3, or Part III, step 3, of Revision 2 of the service bulletin.

Repetitive Inspections: Service Bulletin 737-53A1197

(g) For airplanes identified in Boeing Alert Service Bulletin 737-53A1197, dated August 25, 2006: Do an ultrasound inspection of the slot-shaped cutout in the web for the door stop strap at stringer 16L, an HFEC inspection of the web along the upper and lower edges of the doubler around the doorstop strap at stringer 16L, and a detailed inspection of the web around the doubler for the cutout at stringer 16L, in accordance with the Accomplishment Instructions of the service bulletin. Do the inspections at the applicable time specified in paragraph 1.E. of the service bulletin, except as provided by paragraph (h) of this AD. Do all applicable corrective actions before further flight in accordance with the service bulletin, except as provided by paragraph (i) of this AD. Repeat the inspections at intervals not to exceed 4,500 flight cycles, until accomplishment of the repair/preventive change in accordance with the service bulletin, which terminates the repetitive inspections.

Exceptions to Service Bulletin Specifications

(h) Where Boeing Alert Service Bulletin 737-53A1188, Revision 2, dated May 9, 2007, and Boeing Alert Service Bulletin 737-53A1197, dated August 25, 2006, specify a compliance time after release of the service bulletin, this AD requires compliance within the specified time after the effective date of this AD. For the initial inspection, the grace period for airplanes that have exceeded the specified threshold is extended to 4,500 flight cycles after the effective date of this AD.

(i) Where Boeing Alert Service Bulletin 737-53A1188, Revision 2, dated May 9, 2007, and Boeing Alert Service Bulletin 737-53A1197, dated August 25, 2006, specify to contact Boeing for appropriate action, including repair of damage outside the scope of the service bulletin, repair using a method approved in accordance with the procedures specified in paragraph (j) of this AD.

Alternative Methods of Compliance (AMOCs)

(j)(1) The Manager, Seattle Aircraft Certification Office, FAA, ATTN: Howard Hall, Aerospace Engineer, Airframe Branch, ANM-120S; telephone [phone]; fax [phone]; has the authority to approve AMOCs for this AD, if requested using 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.

Material Incorporated by Reference

(k) You must use Boeing Alert Service Bulletin 737-53A1188, Revision 2, dated May 9, 2007; or Boeing Alert Service Bulletin 737-53A1197, dated August 25, 2006; as applicable; to do the actions required by this AD; unless the AD specifies otherwise.

(1) The Director of the Federal Register approved the incorporation by reference of this service information under 5 U.S.C. 552(a) and 1 CFR part 51.

(2) For service information identified in this AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

(3) You may review copies of the service information incorporated by reference at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to http://www.archives.gov/​federal_​register/​code_​of_​federal_​regulations/​ibr_​locations.html.

Issued in Renton, Washington, on August 6, 2008.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.