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Proposed Rule

Airworthiness Directives; Boeing Model 737-300, -400, and -500 Series Airplanes

Document Details

Information about this document as published in the Federal Register.

Published Document

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AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Supplemental notice of proposed rulemaking; reopening of comment period.

SUMMARY:

This document revises an earlier proposed airworthiness directive (AD), applicable to certain Boeing Model 737-300, -400, and -500 series airplanes, that would have required replacement of the hinge assemblies on certain escape slide compartments of the forward doors with new, stronger hinge assemblies. This new action revises the proposed rule by adding an inspection for incorrectly crimped hinge assemblies, and corrective action if necessary, for certain airplanes. The actions specified by this new proposed AD are intended to prevent forward door escape slides from falling out of their compartments into the airplane interior and inflating, which could impede an evacuation in the event of an emergency. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by October 14, 2003.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2001-NM-88-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 (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2001-NM-88-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 Airplane Group, 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.

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FOR FURTHER INFORMATION CONTACT:

Keith Ladderud, Aerospace Engineer, Cabin Safety and Environmental Systems Branch, ANM-150S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6435; fax (425) 917-6590.

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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 2001-NM-88-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. 2001-NM-88-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to add an airworthiness directive (AD), applicable to certain Boeing Model 737-300, -400, and -500 series airplanes, was published as a notice of proposed rulemaking (NPRM) in the Federal Register on July 9, 2002 (67 FR 45412). That NPRM (the “original NPRM”) would have required replacement of the hinge assemblies on certain escape slide compartments of the forward doors with new, stronger hinge assemblies. The original NPRM was prompted by an investigation that revealed that the soft aluminum hinge assemblies on the escape slide compartments on affected airplanes are susceptible to deformation. That condition, if not corrected, could result in forward door escape slides falling out of their compartments into the airplane interior and inflating, which could impede an evacuation in the event of an emergency.

Comments

Due consideration has been given to the comments received in response to the original NPRM.

Support for the Original NPRM

Several commenters support the original NPRM. One commenter adds that accomplishment of the proposed actions will help eliminate unintended slide deployments on affected airplanes.

Request To Cite Revised Service Bulletin

The manufacturer states that Boeing Service Bulletin 737-25-1430, dated February 22, 2001, misidentifies certain part numbers in the Existing Parts Accountability table. (That service bulletin was cited as the appropriate source of service information for the actions specified in the original NPRM.) The manufacturer advises of the revision of that service bulletin to correct the part number discrepancy, and requests that the original NPRM be revised to cite the revised service bulletin.

The FAA agrees with the request. Revision 1 of the service bulletin, dated April 10, 2003, was issued to correct the part numbers and to add an inspection for incorrectly crimped hinge assemblies for airplanes already modified by the original issue of the service bulletin, which may have not ensured that all hinge assemblies are crimped at one or both ends. An incorrectly crimped hinge assembly may not hold the hinge pin correctly. In this supplemental NPRM: Start Printed Page 54870

  • Paragraph (a) has been revised to limit its applicability to airplanes on which the original issue of the service bulletin has not been done.
  • Paragraph (a) has been revised to cite Revision 1 of the service bulletin.
  • New paragraph (b) has been added to require inspection of airplanes on which the original service bulletin was done.
  • Subsequent paragraphs have been reidentified accordingly.

Request To Withdraw the Proposed AD

One commenter requests withdrawal of the proposed AD as unnecessary. The commenter suggests that the proposed AD was prompted by an isolated incident during which multiple unfavorable conditions existed. The commenter, an operator, reports that, since the early 1990s, its affected airplanes have flown over seven million miles without an escape slide inflating inside the cabin.

The FAA does not agree with the request to withdraw the original NPRM. While few slides have actually inflated inside an airplane, there have been multiple incidents of escape slides dropping out of the closed door-mounted stowage compartment into the passenger compartment. An escape slide that drops out of its compartment could automatically inflate inside the passenger compartment and impede an emergency evacuation. This supplemental NPRM would mandate a design change that will prevent the slide from dropping out of its closed compartment.

Request for Additional Information

One commenter, an operator, suggests that the manufacturer investigate the prevalence of the incident that prompted this AD (i.e., an escape slide dropping out of its closed door-mounted stowage compartment and inflating inside the passenger compartment). The operator asserts its intent to ascertain the background of the unsafe condition by requesting from Boeing all previous correspondence on this issue between the manufacturer and operators.

The FAA acknowledges the comment, although the commenter requests no specific change to the original NPRM. In light of the previous comment and response, the FAA finds it necessary to proceed with this AD action to address the identified unsafe condition.

Request To Extend the Compliance Time

Several commenters request that the proposed compliance time to replace the hinge assemblies be extended from 24 months to 36 months to enable operators to do the work during the normal overhaul schedule for the escape slides.

The FAA agrees with this request. In revising this compliance time, the FAA considered the safety implications, parts availability, and typical maintenance schedules of affected operators. Extending the compliance time to the suggested 36 months will not adversely affect safety but will accommodate the time necessary for the operators to obtain replacement parts and schedule the work. Paragraph (a) of the original NPRM has been revised accordingly in this supplemental NPRM.

Request To Revise Compliance Time

Several commenters request revision of paragraph (b) of the original NPRM (paragraph (c) in this supplemental NPRM), which specifies that certain hinge assemblies may no longer be installed after the effective date of the AD. The commenters request that this compliance time be extended to coincide with the compliance time to replace all hinge assemblies. The commenters state that this extension would give operators more time to update airplane manuals and prevent unforeseen delays if parts are not readily available.

The FAA does not agree. Once an unsafe condition has been identified, the FAA generally prohibits that condition from being introduced (or re-introduced) into the fleet. When it is determined that replacement (safe) parts are immediately available to operators, the FAA typically prohibits installation of the unsafe parts as of the effective date of the AD. While this AD action was being developed, the FAA carefully considered all relevant information including parts availability and determined that sufficient parts would be available to meet operator demand.

Further, the FAA considers the period of time between publication of the final rule in the Federal Register and the effective date of the AD (35 days) sufficient for operators to determine their immediate need for parts and to obtain them. In individual cases where this is not possible, this supplemental NPRM contains a provision (in paragraph (d)) that would allow operators to request an extension of the compliance time, based upon a specific showing of need. The FAA considers that this provision ensures an adequate level of safety without imposing any undue burden on operators.

No change to this supplemental NPRM is necessary regarding this issue.

Request for Coinciding Compliance Times

One commenter questions the timing of this AD in connection with the issuance of AD 2001-15-01, amendment 39-12335 (66 FR 38361, July 24, 2001). AD 2001-15-01 requires modification of the escape slides by modifying the latch assembly and installing a cover assembly on the trigger housing of the inflation cylinder. The commenter advises that the two ADs will require closely associated work at different times. The FAA infers that the commenter requests harmonization of the ADs' compliance times.

The FAA does not agree. The compliance time for AD 2001-15-01 is 18 months for some actions and 36 months for the remaining actions, effective from August 28, 2001. Therefore, a coordinated work schedule for the two ADs would necessitate a shorter compliance time for the proposed requirements in this supplemental NPRM. As stated previously, the FAA finds the proposed compliance time'extended to 36 months as requested'to be adequate. No further change to this supplemental NPRM is necessary regarding the compliance time.

Request To Provide Alternative Actions

One commenter requests that the original NPRM be revised to provide for the option of repetitively inspecting and testing the hinge assemblies, instead of replacing them within the specified compliance time. The commenter states that the alternative repetitive inspections would prevent the unnecessary replacement of functional parts.

The FAA does not agree, based on the determination that the subject hinge assemblies are weak and must be replaced within the proposed compliance time. The FAA has determined that long-term continued operational safety will be better ensured by modifications or design changes to remove the source of the problem, rather than by repetitive inspections. Long-term inspections may not provide the degree of safety assurance necessary for the transport airplane fleet. This, coupled with a better understanding of the human factors associated with numerous repetitive inspections, has led the FAA to consider placing less emphasis on special procedures and more emphasis on design improvements. The proposed modification requirement is consistent with these considerations. No further Start Printed Page 54871change to this supplemental NPRM is necessary regarding this issue.

Request To Allow Alternative Finishes

One commenter prefers that the service bulletin avoid specifying the finish (for the primer or topcoat) to be used to conceal the flush rivets. Because some operators may have already painted the container assemblies with an unspecified finish, the operator suggests that the original NPRM be revised to specifically allow use of an “equivalent” finish.

The FAA does not agree. An “operator's equivalent procedure” may be used only if approved as an alternative method of compliance (AMOC) in accordance with paragraph (d) of this supplemental NPRM. No change to this supplemental NPRM is necessary regarding this issue.

Request To Revise Reference to Service Bulletin Figure

One operator suggests that Boeing Service Bulletin 737-25-1430 depicts the latch assembly in use before AD 2001-15-01 was issued. This latch assembly, part number 65C19901-20, is depicted in Figure 2, Sheet 2 of 6, of that service bulletin. The commenter suggests this was an oversight, but expresses concern about the potential confusion it may raise for other operators. The FAA infers that the commenter requests that reference to this figure be revised or removed from the proposed AD.

The FAA agrees. As stated earlier, this supplemental NPRM has been revised to cite Revision 1 of the service bulletin, which includes the commenter's suggested change.

Request To Revise Part Reidentification Method

One commenter requests a revision of the method of reidentification (reidentifying the part number) specified in the original NPRM. The commenter doubts that the existing part number would be present on all affected escape slide covers, which may have been subject to prior maintenance, repair, or repainting. The commenter suggests reidentifying the reworked escape slide compartment by adding “SB 737-25-1430 Compliant” adjacent to any existing part numbers.

The FAA does not agree with the request. Reidentification with the new part number, as proposed in this supplemental NPRM, would ensure that the correct part number is installed. However, the FAA may consider requests for AMOCs if submitted with detailed procedures that would ensure an acceptable level of safety, under the provisions of paragraph (d) of this supplemental NPRM.

Request To Revise Description of Unsafe Condition

The manufacturer states that an escape slide released from its compartment into the airplane interior would not always automatically inflate. The commenter requests that the original NPRM be revised to imply only the potential for the slide to inflate—the slide “could,” rather than “would,” automatically inflate. The original NPRM refers to one incident of the escape slide inflating inside the airplane; in that instance, the commenter suggests that the severe swerving motion of the airplane likely caused the escape slide to move across the floor and inflate. The FAA infers that the commenter requests that the discussion of the unsafe condition identified in the original NPRM be reworded accordingly.

The FAA agrees that the commenter's suggested wording is clearer than the wording in the Discussion section of the original NPRM. Although this supplemental NPRM does not repeat that section, the events associated with the identified unsafe condition are clarified in the discussion under “Request to Withdraw the Proposed AD.”

Request To Revise Cost Estimate

Several commenters report that the price of the replacement parts has increased since the original NPRM was issued. The manufacturer has confirmed that the current parts cost is $1,569. The Cost Impact section has been revised accordingly in this supplemental NPRM.

Additional Changes to the Original NPRM

In the original NPRM, the heading for paragraph (b) is “Spare Parts.” In this supplemental NPRM, the heading for that paragraph (reidentified as paragraph (c)) has been renamed “Part Installation” to more accurately define the proposed requirement.

Conclusion

Since certain changes expand the scope of the original NPRM, the FAA has determined that it is necessary to reopen the comment period to provide additional opportunity for public comment.

Cost Impact

There are approximately 1,974 airplanes of the affected design in the worldwide fleet. The FAA estimates that 793 airplanes of U.S. registry would be affected by this supplemental NPRM.

Replacement of the hinge assemblies, if necessary, would take approximately 5 work hours per airplane, at an average labor rate of $65 per work hour. Required parts would cost approximately $1,569 per airplane. Based on these figures, the cost impact of the proposed hinge replacement is estimated to be $1,894 per airplane.

The inspection, if necessary, would take approximately 1 to 3 work hours per airplane, at an average labor rate of $65 per work hour. Based on these figures, the cost impact of the proposed inspection is estimated to be $65 to $195 per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the 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.

Start List of Subjects

List of Subjects in 14 CFR Part 39

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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:

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PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Start Authority

Authority: 49 U.S.C. 106(g), 40113, 44701.

End Authority
[Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

Boeing: Docket 2001-NM-88-AD.

Applicability: Model 737-300, -400, and -500 series airplanes; certificated in any category; as listed in Boeing Special Attention Service Bulletin 737-25-1430, Revision 1, dated April 10, 2003.

Compliance: Required as indicated, unless accomplished previously.

To prevent forward door escape slides from falling out of their compartments into the airplane interior and inflating, which could impede an evacuation in the event of emergency, accomplish the following:

Hinge Assembly Replacement

(a) For airplanes on which the hinge assemblies have not been replaced as of the effective date of this AD in accordance with Boeing Special Attention Service Bulletin 737-25-1430, dated February 22, 2001: Within 36 months after the effective date of this AD, replace the hinge assemblies on the escape slide stowage compartments of the forward doors with new, stronger hinge assemblies, in accordance with Part 1 of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-25-1430, Revision 1, dated April 10, 2003.

Hinge Assembly Inspection

(b) For airplanes on which the hinge assemblies were replaced before the effective date of this AD in accordance with Boeing Special Attention Service Bulletin 737-25-1430, dated February 22, 2001: Within 36 months after the effective date of this AD, perform a general visual inspection for incorrectly crimped hinge assemblies, in accordance with Part 2 of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-25-1430, Revision 1, dated April 10, 2003. If any hinge assembly is not correctly crimped, perform corrective action before further flight in accordance with Revision 1 of the service bulletin.

Note 1:

For the purposes of this AD, a general visual inspection is defined as: “A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity. This level of inspection is made from within touching distance unless otherwise specified. A mirror may be necessary to enhance visual access to all exposed surfaces in the inspection area. This level of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight, or droplight and may require removal or opening of access panels or doors. Stands, ladders, or platforms may be required to gain proximity to the area being checked.”

Part Installation

(c) As of the effective date of this AD, no person may install a hinge assembly P/N 65C30431-6 or 65C30431-7 on any airplane.

Alternative Methods of Compliance

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

Start Signature

Issued in Renton, Washington, on September 15, 2003.

Ali Bahrami,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. 03-23936 Filed 9-18-03; 8:45 am]

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