AD 98-06-21

This amendment adopts a new airworthiness directive (AD), applicable to certain British Aerospace BAe Model ATP airplanes, that requires repetitive inspections to detect uneven wear of the heat pack of the main landing gear (MLG) brake unit; measurement and setting of the wear remaining length (WRL) of the wear indicator pin (WIP); and replacement of the brake heat pack unit with a serviceable unit, if necessary. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to detect uneven wear of the brake heat pack unit and prevent failure of the pressure stator of the MLG brake unit, which could result in reduced braking efficiency and consequent longer stopping distances upon landing.

Final rule

98-06-21 BRITISH AEROSPACE REGIONAL AIRCRAFT [Formerly Jetstream Aircraft Limited; British Aerospace (Commercial Aircraft) Limited]: Amendment 39-10399. Docket 96-NM-200-AD.
Applicability: BAe Model ATP airplanes having constructors numbers 2002 through 2067 inclusive, certificated in any category.

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 (c) 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 detect uneven wear of the brake heat pack unit and prevent failure of the pressure stator of the main landing gear (MLG) brake unit, which could result in reduced braking efficiency and consequent longer stopping distances upon landing, accomplish the following:

NOTE 2: Accomplishment of the actions required by paragraphs (a) and (b) of this AD prior to the effective date of this AD in accordance with Jetstream Service Bulletin ATP/J61-32-71, dated May 23, 1996, is considered acceptable for compliance with the applicable actions specified in this amendment.

(a) Within 300 hours time-in-service (TIS) after the effective date of this AD: Perform an inspection of the brake units of the left and right MLG to detect uneven wear at the pressure stator/first rotor interface, measure the wear remaining length (WRL) of the wear indicator pin (WIP), and accomplish the action specified in paragraph (a)(1) or (a)(2) of this AD, as applicable; in accordance with Jetstream Service Bulletin ATP/J61-32-71, Revision 1, dated June 18, 1996.

NOTE 3: Jetstream Service Bulletin ATP/J61-32-71, dated May 23, 1996, and Revision 1, dated June 18, 1996, reference Dunlop Service Bulletin AHA1612/AHA2004-32-1122, dated April 16, 1996, as an additional source of service information for procedures to inspect the brakes, measure the WRL of the WIP, and set the corrected length of the pin.

(1) If the WRL of the WIP is greater than or equal to 0.5 inches: Repeat the action required in paragraph (a) of this AD thereafter at intervals not to exceed 300 hours TIS.

(2) If the WRL of the WIP is less than 0.5 inches: Prior to further flight, measure the thickness of the pressure stator and accomplish the action specified in paragraph (a)(2)(i) or (a)(2)(ii) of this AD, as applicable; and repeat the action required in paragraph (a) of this AD thereafter at intervals not to exceed 300 hours TIS.

(i) If the pressure stator is less than or equal to 0.31 inches thick: Replace the heat pack of the MLG brake unit with a serviceable unit and set the WRL of the WIP to indicate the corrected WRL measurement.

(ii) If the pressure stator exceeds 0.31 inches thick: Set the WRL of the WIP to indicate the corrected WRL measurement.

(b) If, during any inspection required by this AD, the WRL of the WIP on any brake unit shows that the wear status of the brake heat pack is not within the acceptable limits specified in Jetstream Service Bulletin ATP/J61-32-71, dated May 23, 1996, or Revision 1, dated June 18, 1996: Prior to further flight, replace the brake heat pack unit with a serviceable unit in accordance with Jetstream Service Bulletin ATP/J61-32-71, Revision 1, dated June 18, 1996; and repeat the action required in paragraph (a) of this AD thereafter at intervals not to exceed 300 hours TIS.

(c) An alternative method of compliance or adjustment of the initial compliance time that provides an acceptable level of safety may be used if approved by the Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add additional comments, and then send it to the Manager, International Branch, ANM-116.

NOTE 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the International Branch, ANM-116.

(d) 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.

(e) The actions shall be done in accordance with Jetstream Service Bulletin ATP/J61-32-71, Revision 1, dated April 16, 1996, which contains the specified effective pages:

Page Number
Revision Level
Shown on Page
Date
Shown on Page
1, 3
1
June 18, 1996
2, 4, 5
Original
May 23, 1996

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 AI(R) American Support, Inc., 13850 McLearen Road, Herndon, Virginia 20171. 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.

NOTE 5: The subject of this AD is addressed in British airworthiness directive 002-05-96.

(f) This amendment becomes effective on April 23, 1998.

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 British Aerospace BAe Model ATP airplanes was published in the Federal Register on November 26, 1997 (62 FR 63042). That action proposed to require repetitive inspections to detect uneven wear of the heat pack of the main landing gear (MLG) brake unit; measurement and setting of the wear remaining length (WRL) of the wear indicator pin (WIP); and replacement of the brake heat pack unit with a serviceable unit, if necessary.

Comments
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

One commenter supports the proposed rule.

One commenter requests that the proposal be withdrawn because no instances of uneven brake wear of the brake heat pack have occurred. The commenter states thatits airplanes have the lowest brake life of the worldwide fleet of the affected airplanes, the operating environment is different from all other operators of these airplanes models, and that, during maintenance, the whole brake assembly (rather than just the brake heat packs) are changed.

The FAA does not concur with the commenter s request to withdraw the proposal. As explained in the preamble of the proposal, this action was prompted by reports indicating that the heat pack unit of the main landing gear brake unit exhibited uneven wear at the pressure stator/first rotor interface in some instances, which resulted in a small number of failures of the pressure stator. In light of these reports, the FAA identified the existence of an unsafe condition that is likely to exist or develop in the affected airplanes. As a result, the FAA is issuing this AD to eliminate that unsafe condition by requiring repetitive inspections to detect uneven wear of the heat pack; measurement and setting of the wear remaining length of the wear indicator pin; and replacement of the brake heat pack unit with a serviceable unit, if necessary. The AD is the appropriate vehicle for mandating such actions.

Removal of Service Bulletin Citation
The FAA has revised this final rule to move references to Jetstream Service Bulletin ATP/J61-32-71, dated May 23, 1996, from paragraphs (a) and (b) of this AD to a new "NOTE 2." This new note indicates that accomplishment of the actions required by those paragraphs prior to the effective date of this AD in accordance with the original issue of the service bulletin is considered acceptable for compliance with those actions. The FAA has determined that the actions recommended by the original issue of the service bulletin are essentially identical to those specified in Revision 1. Therefore, the FAA finds that it is appropriate to cite the latest revision of the service bulletin and reference the original issue in a note.

Conclusion
Aftercareful 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 as proposed.

Cost Impact
The FAA estimates that 10 airplanes of U.S. registry will be affected by this AD, that it will take approximately 5 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $3,000, or $300 per airplane.

The cost impact figure discussed above is 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.

Regulatory Impact
The regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of powerand responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

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."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (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. Section 39.13 is amended by adding the following new airworthiness directive: