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Proposed Rule

Airworthiness Directives; Boeing Model 747, 757, 767, and 777 Series Airplanes

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Information about this document as published in the Federal Register.

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Start Preamble

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747, 757, 767, and 777 series airplanes. This proposal would require modification of certain drip shields located on the flight deck, and follow-on actions. This action is necessary to prevent potential ignition of the moisture barrier cover of the drip shield, which could propagate a small fire that results from an otherwise harmless electrical arc, leading to a larger fire. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by September 25, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-217-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 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. 2000-NM-217-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 for Windows 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.

Start Further Info

FOR FURTHER INFORMATION CONTACT:

James Cashdollar, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2785; fax (425) 227-1181.

End Further Info End Preamble Start Supplemental Information

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 notice 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 notice must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2000-NM-217-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. 2000-NM-217-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received a report that; on certain Boeing Model 747, 757, 767, and 777 series airplanes; the airplane manufacturer found some drip shields assembled with the moisture barrier cover bonded to the insulation and multiple insulation layers bonded together using a non-flame-resistant adhesive. Such assembly of the drip shield reduces the fire resistance of the moisture barrier cover and insulation. As a result, the drip shield assemblies do not meet the requirements of Section 25.853 (“Fire Protection: Compartment Interiors”) of the Federal Aviation Regulations (14 CFR 25.853). This condition, if not corrected, could result in potential ignition of the moisture barrier cover of the drip shield, which could propagate a small fire that results from an otherwise harmless electrical arc, leading to a larger fire.

Other Relevant Rulemaking

On May 19, 2000, the FAA issued AD 2000-11-01, amendment 39-11749 (65 FR 34322, May 26, 2000), which is applicable to certain McDonnell Douglas Model DC-9-80 and MD-90-30 series airplanes and Model MD-88 airplanes; and AD 2000-11-02, amendment 39-11750 (65 FR 34341, May 26, 2000), which is applicable to certain McDonnell Douglas Model DC-10-10F, DC-10-15, DC-10-30, DC-10-30F, DC-10-40, MD-11, and MD-11F series airplanes. These AD's require determination of whether, and at what locations, insulation blankets made of metallized polyethyleneteraphthalate (MPET) are installed, and replacement of any MPET insulation blankets with new blankets made of metallized Tedlar or equivalent blanket material. Those AD's were prompted by reports of fires (in flight and on the ground) on certain airplanes equipped with MPET insulation blankets. Such insulation blankets could propagate a small fire that is the result of an otherwise harmless electrical arc, and could result in a much larger fire.

The unsafe condition addressed by those AD's is similar to that addressed in this proposed AD. The material used to manufacture the drip shields that are the subject of this AD can be ignited by a small ignition source and propagate a fire in a manner similar to the MPET insulation blankets. However, while AD 2000-11-01 and AD 2000-11-02 require replacement of MPET insulation blankets with new blankets, this proposed AD would require isolation of the drip shields from all potential Start Printed Page 48951ignition sources rather than replacement of the drip shields. The decision to mandate modification of the drip shields rather than replacement of the drip shields with new drip shields made of another material is based on the difficulties associated with removing the drip shields from the airplane (for example, disassembly of flight deck and disconnection of wiring for flight controls). The FAA finds that, in lieu of replacement of the drip shields, modification of the drip shields to isolate them from all potential ignition sources will ensure an acceptable level of safety.

A similar unsafe condition exists related to fiberglass insulation installed on the ducts of the environmental control system (ECS) on certain Boeing Model 737, 747, 757, and 767 series airplanes. During fire testing, samples of fiberglass insulation from the ECS ducts, with BMS8-142 vapor barrier bonded to the outer surface of the insulation with BAC5010 Type 97 adhesive, burned at a rate faster than allowed by Section 25.853 (“Fire Protection: Compartment Interiors”) of the Federal Aviation Regulations (14 CFR 25.853). This condition, if not corrected, could result in potential ignition of fiberglass insulation in the ECS ducts, which could propagate a small fire and lead to a larger fire. A separate rulemaking action [notice of proposed rulemaking, Rules Docket No. 2000-NM-226-AD] is being issued to address that unsafe condition on affected airplanes.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletins 747-25-3253, 767-25-0290, and 777-25-0164; all including Appendices A, B, and C; all dated June 29, 2000; and 757-25-0226 and 757-25-0228; both including Appendices A, B, and C; both dated July 3, 2000. These service bulletins describe procedures for modification of certain drip shields located on the flight deck, and follow-on actions. The modification involves installation of fire blocks in areas where the drip shields are exposed to potential ignition sources. The fire block consists of fire-resistant flexible cargo liner fabric as a primary barrier. For large gaps between the drip shield and structure, the fire block uses fire-resistant foam and glass fabric. As follow-on actions, the service bulletins describe procedures for a one-time functional test of any system disturbed during the modification of the drip shields, and installation of placards to inform maintenance personnel that the drip shields have been fire blocked and any modification must be accomplished in accordance with the applicable service bulletin. Accomplishment of the actions specified in the service bulletins is intended to adequately address the identified unsafe condition.

In addition, Boeing Service Bulletins 747-25-3253 and 767-25-0290 describe procedures to allow sampling of the insulation and adhesive of the drip shields on certain airplanes, in lieu of the modification described above. The service bulletins recommend that operators take samples of the drip shields on these airplanes and submit the samples to Boeing for testing. If the testing of all of the samples yields positive results, modification of the airplane with fire blocks is not necessary. If the testing is negative, the airplane must be modified in accordance with the applicable service bulletin.

Explanation of Requirements of Proposed Rule

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 the actions specified in the applicable service bulletins described previously, except as discussed below. For Model 747 and 767 series airplanes listed in Group 1 in the applicable service bulletins, the proposed AD would allow accomplishment of the optional sampling of drip shields described previously.

Differences Between Proposed Rule and Service Bulletins

Operators should note that the service bulletins specify that the modification of the drip shields is to be accomplished at the next heavy maintenance check. The FAA finds that such a compliance time will not ensure that the modifications are accomplished in a timely manner. In developing an appropriate compliance time for this AD, the FAA considered not only the manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition, as well as the compliance time for the actions required by the previously described AD 2000-11-01 and AD 2000-11-02. AD 2000-11-01 and AD 2000-11-02 require replacement of MPET insulation blankets on affected airplanes within five years after June 30, 2000 (the effective date of those AD's). In light of all of these factors, and especially the similarity of the unsafe condition addressed in this proposed AD to that addressed in the AD's described previously, the FAA finds a compliance time of five years after the effective date of this AD for initiating the proposed actions to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.

In addition, operators should note that the service bulletins specify that methods for modification of any areas of the drip shield where wires or equipment were added on the outboard surface of the drip shield (that is, between the drip shield and the airplane structure) “must be approved separately.” However, the service bulletins do not specify who must approve these methods. Therefore, paragraph (b) of this proposed AD specifies that modification of these areas must be accomplished in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA.

Operators also should note that, although Boeing Service Bulletin 777-25-0164 does not direct operators to perform a functional test on any system disturbed during the modification of the drip shield, the FAA has determined that such a functional test is necessary. Therefore, the functional tests required by paragraph (a)(2) of this AD applies to all airplanes affected by this AD. The functional tests must be accomplished in accordance with the applicable chapter of the applicable Airplane Maintenance Manual (AMM). Also, none of the relevant service bulletins specify corrective actions if any functional test fails. Therefore, paragraph (a)(2) of this AD requires, if any functional test fails, isolation of the fault, correction of the discrepancy in accordance with the applicable AMM, and repetition of the failed test until it is successfully accomplished.

Cost Impact

There are approximately 3,137 airplanes of the affected design in the worldwide fleet. The FAA estimates that 999 airplanes of U.S. registry would be affected by this proposed AD. The following table shows the estimated cost impact for airplanes affected by this AD. The average labor rate is $60 per work hour. The estimated maximum total cost for all airplanes affected by this proposed AD is $3,695,460. Start Printed Page 48952

ModelU.S.- registered airplanesWork hours (estimated)Labor cost (estimated)Parts cost (estimated)Maximum fleet cost (estimated)
74719439$2,340$2,300 to 3,500$1,132,960
757491261,5601,7001,600,660
767258171,0202,300856,560
7775631801,700105,280

For Model 747 and 767 series airplanes listed in Group 1 in the applicable service bulletin, in lieu of accomplishment of the modification of the drip shields, this proposed AD provides an option to take samples of the drip shields to determine if the modification is necessary. Therefore, the cost impact of this proposed AD as presented above may be reduced if some airplanes do not need the modification. For airplanes that accomplish the sampling, it would take approximately 18 work hours, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the sampling on affected U.S. operators is estimated to be $1,080 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 proposed 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.

The manufacturer has advised the FAA that warranty remedies may be available for parts and labor costs associated with accomplishing the actions that would be required by this proposed AD. Therefore, the future economic cost impact of this rule on U.S. operators may be less than the cost impact figures indicated above.

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

End List of Subjects

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:

Start Part

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 2000-NM-217-AD.

Applicability: Model 747, 757, 767, and 777 series airplanes having the line numbers listed below; certificated in any category.

ModelAffected line numbers (L/N)Except L/N
7471 through 1234 inclusive1174, 1216
7572 through 895 inclusive870, 886, 894
7671 through 768 inclusive758
7772 through 254 inclusive120, 219, 230, 235, 242, 245, 249

Note 1:

This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (d) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To prevent potential ignition of the moisture barrier cover of the drip shield, which could propagate a small fire that results from an otherwise harmless electrical arc, leading to a larger fire, accomplish the following:

Modification

(a) Within 5 years after the effective date of this AD, accomplish paragraphs (a)(1), (a)(2), and (a)(3) of this AD; in accordance with Boeing Service Bulletin 747-25-3253, 767-25-0290, or 777-25-0164; all including Appendices A, B, and C; all dated June 29, 2000; or 757-25-0226 or 757-25-0228; both including Appendices A, B, and C; both dated July 3, 2000; as applicable; except as provided by paragraph (b) of this AD.

(1) Modify drip shields located on the flight deck by installing fire blocks.

(2) Prior to further flight following accomplishment of paragraph (a)(1) of this AD, perform a functional test of any system disturbed by the modification, in accordance with the applicable service bulletin or the Airplane Maintenance Manual (AMM), as applicable. If any functional test fails, prior to further flight, isolate the fault, correct the Start Printed Page 48953discrepancy in accordance with the applicable AMM, and repeat the failed test until it is successfully accomplished.

(3) Prior to further flight following the accomplishment of paragraphs (a)(1) and (a)(2) of this AD, install placards on all modified drip shields.

(b) If any wires or equipment are installed on the outboard surface of the drip shield (that is, between the drip shield and the airplane structure), modify that area in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA.

Optional Sampling (Certain Model 747 and 767 Series Airplanes)

(c) For Model 747 and 767 series airplanes listed in Group 1 in Boeing Service Bulletins 747-25-3253 and 767-25-0290: In lieu of accomplishment of paragraph (a) of this AD, within 5 years after the effective date of this AD, collect samples of the insulation and adhesive of the drip shields, and submit the samples to the manufacturer for testing, in accordance with Boeing Service Bulletin 747-25-3253 or 767-25-0290; both including Appendices A, B, and C; both dated June 29, 2000; as applicable.

(1) If the test on all samples is positive, no further action is required by this AD.

(2) If the test on any sample is negative, accomplish paragraph (a) of this AD before the compliance time specified in that paragraph.

Alternative Methods of Compliance

(d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO.

Note 2:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

Special Flight Permits

(e) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

Start Signature

Issued in Renton, Washington, on August 4, 2000.

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

[FR Doc. 00-20243 Filed 8-9-00; 8:45 am]

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