Federal Aviation Administration, DOT.
This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737, 747, 757, and 767 series airplanes, that requires rework of certain duct assemblies of the environmental control system (ECS) or replacement of the duct assemblies with new or reworked duct assemblies. This action is necessary to prevent potential ignition of fiberglass insulation material installed on the outside of the ECS ducts, which could propagate a small fire and lead to a larger fire. This action is intended to address the identified unsafe condition.
Effective February 2, 2001.
The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of February 2, 2001.
The service information referenced in this AD may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.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
A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 737, 747, 757, and 767 series airplanes was published in the Federal Register on August 10, 2000 (65 FR 48947). That action proposed to require rework of certain duct assemblies of the environmental control system (ECS) or replacement of the duct assemblies with new or reworked duct assemblies.
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
Support for the Proposal
Two commenters support the proposed rule.
Requests to Revise Compliance Time
Several commenters request an extension of the proposed compliance time. Generally, the commenters claim that the proposed five-year compliance time will result in a need to accomplish the proposed requirements on some airplanes before the next scheduled heavy maintenance visit, which would cause significant airplane down time, and would impose a substantial cost penalty. Individual comments are presented below.
One of the commenters suggests that an extension of the compliance time to six years for all aircraft types would not compromise safety any further. Another commenter requests that the compliance time be stated as follows: “* * * within five years after the effective date of the AD, or at the next scheduled heavy maintenance visit, whichever occurs later, not to exceed eight years after the effective date.” This commenter performs segmented “C” checks approximately every two years, and it takes four such checks to reach all areas of the airplane. Therefore, under that commenter's maintenance program, access to the specific areas affected may not occur for eight years.
The Air Transport Association (ATA) of America, on behalf of its members, states that the compliance time should be stated as follows: “* * * within five years after the effective date of this AD, or at the next scheduled heavy maintenance visit, whichever occurs later, not to exceed six years after the effective date.” The ATA contends that this compliance time “would preclude the press associated with significant, unscheduled maintenance visits”; in practical terms, this would affect the installation time of less than 20 percent of the applicable airplanes. The ATA believes that its suggested compliance time would achieve a level of safety equivalent to that intended by the proposed AD.
Another commenter states that it participated in a Boeing-hosted meeting on the subject ECS ducting flammability concerns and asked Boeing to recommend to the FAA that the actions be required during a heavy maintenance visit. The commenter notes that Boeing did indeed make this recommendation to the FAA in the referenced FAA-approved service bulletins. The commenter says that six years would facilitate making use of the first heavy maintenance visit under current maintenance programs. The commenter adds that compliance periods that intend to make use of scheduled down time per an approved maintenance program should reflect an interval taking into account such approved maintenance programs.
Another commenter states that a moderate escalation of the compliance time to 6 years would avoid burdening the operators with excessive costs, and would allow accomplishment of the modification at a heavy maintenance visit. Retaining the proposed 5-year compliance time for Model 757 series Start Printed Page 82899airplanes would require that approximately 17 percent of the fleet (15 airplanes) undergo the modifications at a light or special maintenance visit, which would impose an undue financial burden on some operators.
The commenter adds that a comparison between the compliance time specified in this proposed rule to that given in two previously issued AD's that address similar unsafe conditions cannot be used as a basis for the choice of a compliance time for this proposed rule. [The AD's referenced by the commenter are AD 2000-11-01, amendment 39-11749 (65 FR 34322, May 26, 2000), and AD 2000-11-02, amendment 39-11750 (65 FR 34341, May 26, 2000). Those AD's require replacement of metallized Mylar insulation blankets with new blankets made of more flame-resistant material on certain McDonnell Douglas airplanes.] Based on information about various heavy maintenance intervals provided by the commenter, the operators of airplanes affected by AD 2000-11-01 and AD 2000-11-02 would not be subjected to excessive modification costs since all of the affected airplanes could be modified during a heavy maintenance visit within the 5-year compliance time specified in those two AD's.
The FAA concurs that the compliance time can be extended somewhat. The FAA has closely reviewed the rationale presented by the commenters. In addition, the FAA has examined related comments to AD 2000-11-01 and AD 2000-11-02. In those AD's, the compliance time was extended from four to five years in the final rules.
The FAA acknowledges that a compliance time of six years will more closely align with heavy maintenance visits. Paragraph (a) of the final rule has been revised accordingly. For any operator that performs segmented “C” checks every two years, the revised compliance time should allow enough time to schedule the ducting rework or replacement during one of the next three such checks. The extension of the compliance time also will minimize the amount of unscheduled work and associated down time. The FAA considers that this extension of the compliance time will not adversely affect safety.
Request for Sampling Program
One commenter requests that a sampling program be incorporated for all fleet types affected to determine if BAC 5010, Type 97 adhesive was used on specific airplanes and to establish the requirements for replacing the ECS ducts. The commenter states that neither Boeing nor the FAA has provided concrete evidence that BAC 5010, Type 97 adhesive was used in the assembly of all the ECS ducts. The commenter adds that the applicable service bulletins and proposed rule are based purely on conjecture. The commenter suggests that negative findings in such a sampling program would offer terminating action for the proposed rule.
The FAA does not concur. The FAA finds that there is a significant amount of evidence pointing to widespread use of unsafe adhesives (that is, material and adhesive combinations that are easily ignited and consequently able to propagate a small fire) on Model 737, 747, 757, and 767 series airplanes. Determining which ECS ducts are affected has already been accomplished to a great extent through the efforts of Boeing. The scope of the parts and airplanes affected by the final rule has been significantly reduced through Boeing's efforts in surveying its duct suppliers. Only airplanes having parts that were made by suppliers that used unsafe adhesives in their manufacturing processes have been included in the applicability of this final rule. Although it is possible that some parts may have been manufactured using compliant adhesives, the FAA expects that almost all were manufactured using the BAC 5010, Type 97 adhesive because it is much easier to apply than other types of adhesives. Therefore, the FAA has determined that an option for a sampling program would not provide sufficient value and has not included such an option in this final rule.
However, an operator may request approval of an alternative method of compliance in accordance with the provisions of paragraph (b) of this final rule, provided that evidence is submitted to show that no unsafe adhesive was used in the construction of the ECS ducting on the airplanes in its fleet.
Request for Clarification of Discussion Section
One commenter requests that certain portions of the Discussion section of the proposed rule be rewritten. The commenter specifically asks that this section include the FAA's actual safety concerns, which are that the material is too easy to ignite and is not self-extinguishing. The commenter also asks that the section include a statement indicating that a small electrical arc would be sufficient to ignite the fiberglass insulation material, if this is indeed the case.
Although the Discussion section of the proposed rule is not restated in the final rule, the FAA acknowledges that the commenter's statements are correct. The purpose for issuing this AD is to prevent ignition of insulation material by a small arc, which would then not self-extinguish, but would instead propagate a fire.
After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.
There are approximately 1,162 airplanes of the affected design in the worldwide fleet. The FAA estimates that 403 airplanes of U.S. registry will be affected by this AD. The following table shows the estimated cost impact of the required actions for airplanes affected by this AD. The average labor rate is $60 per work hour. The estimated total cost for all airplanes affected by this AD is $2,552,996.
|Model||U.S.- Registered airplanes||Estimated work hours||Estimated labor cost||Estimated parts cost||Estimated fleet cost|
The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the 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.
The manufacturer has advised the FAA that warranty remedies may be available for parts and labor costs associated with accomplishing the actions that are required by this AD. Therefore, the future economic cost impact of this rule on U.S. operators may be less than the cost impact figures indicated above.
The regulations adopted herein 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. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132.
For the reasons discussed above, I certify that this action (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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption ADDRESSES.Start List of Subjects
List of Subjects in 14 CFR Part 39End List of Subjects
Adoption of the AmendmentStart Amendment Part
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (End Amendment Part Start Part
PART 39—AIRWORTHINESS DIRECTIVESEnd Part Start Amendment Part
1. The authority citation for part 39 continues to read as follows:End Amendment Part
2. Section 39.13 is amended by adding the following new airworthiness directive:End Amendment Part
2000-26-05 Boeing: Amendment 39-12055. Docket 2000-NM-226-AD.
Applicability: Model 737-300, 737-400, 737-500, 747, 757-200, 757-300, 767-200, 767-300, and 767-300F sries airplanes, certificated in any category, having the line numbers listed in the following table:
|Model||Affected line numbers (L/N)||Except L/N|
|737-300, -400, -500,||2591, 2601, 2720, 2723, 2730, 2733, 2734, 2736 through 2850 inclusive, 2852 through 3126 inclusive||N/A|
|747||1011 through 1233 inclusive||1012, 1174, 1216|
|757-200, -300||580 through 895 inclusive||581, 583 through 586 inclusive, 589, 595, 609, 613, 615, 622, 624, 626, 669, 674|
|767-200, -300, -300F||521 through 767 inclusive,||522, 525, 718, 758 770|
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 (b) 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 fiberglass insulation in the environmental control system (ECS) ducts, which could propagate a small fire and lead to a larger fire, accomplish the following:
Rework or Replacement
(a) Within 6 years after the effective date of this AD, rework ECS duct assemblies or replace existing duct assemblies with new or reworked duct assemblies, in accordance with Boeing Alert Service Bulletins 737-21A1129, 747-21A2416, 757-21A0084, 757-21A0085, or 767-21A0158; all including Appendices A and B; all dated June 29, 2000; as applicable.
Alternative Methods of Compliance
(b) 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 Aircraft Certification Office (ACO), FAA. 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.
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
(c) Special flight permits may be issued in accordance with §§ 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.
Incorporation by Reference
(d) The actions shall be done in accordance with Boeing Alert Service Bulletin 737-21A1129, including Appendices A and B; dated June 29, 2000; Boeing Alert Service Bulletin 747-21A2416, including Appendices A and B; dated June 29, 2000; Boeing Alert Service Bulletin 757-21A0084, including Appendices A and B; dated June 29, 2000; Boeing Alert Service Bulletin 757-21A0085, including Appendices A and B; dated June 29, 2000; or Boeing Alert Service Bulletin 767-21A0158; including Appendices A and B; dated June 29, 2000. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplane Group, Start Printed Page 82901P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
(e) This amendment becomes effective on February 2, 2001.Start Signature
Issued in Renton, Washington, on December 20, 2000.
John J. Hickey,
Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 00-33018 Filed 12-28-00; 8:45 am]
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