AD 94-08-12

This amendment adopts a new airworthiness directive (AD), applicable to certain Aerospatiale Model ATR72 series airplanes, that requires inspections to detect cracking in the brake side half hub in the bearing housing area of certain main landing gear (MLG) wheels, and replacement of the MLG wheel, if necessary. This amendment also requires the eventual replacement of certain MLG wheels with other wheels, as terminating action for the repetitive inspections. This amendment is prompted by in-service experience that indicates the possibility of fatigue cracking occurring in the subject area. The actions specified by this AD are intended to prevent failure of the brake side half hub due to fatigue cracking, which could lead to separation of the MLG wheel and tire from the axle.

Final rule.

94-08-12 AEROSPATIALE: Amendment 39-8884. Docket 93-NM-184-AD.

Applicability: Model ATR72 airplanes; equipped with Dunlop main landing gear (MLG) wheels, part number AHA1752 Pre Mod 6; certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent failure of the brake side half hub due to fatigue cracking, which could lead to separation of the MLG wheel and tire from the axle, accomplish the following:

(a) At the next tire change after the effective date of this AD, or within 60 days after the effective date of this AD, whichever occurs later, conduct an eddy current inspection to detect cracking in the bearing housing of the brake side half hub of Dunlop MLG wheels, part number AHA1752 Pre Mod 6, in accordance with the Accomplishment Instructions of Dunlop Limited, Aviation Division, Service Bulletin AHA1752-32-1069, dated June 28, 1993.

(b) If no cracking is detected, repeat the inspection specified in paragraph (a) of this AD thereafter at every tire change until the requirements of paragraph (d) of this AD are accomplished.

(c) If any cracking is detected, prior to further flight, accomplish one of the following:

(1) Replace the complete MLG wheel with a serviceable MLG wheel having part number AHA1752 Pre Mod 6. Thereafter, repeat the inspections specified in paragraph (a) of this AD at every tire change. Or

(2) Replace the complete MLG wheel with a MLG wheel having part number AHA1752 Post Mod 6. Such replacement constitutes terminating action for the inspection requirements of this AD. Or

(3) Replace the complete MLG wheel with a MLG wheel having part number AHA1890. Such replacement constitutes terminating action for the inspection requirements of this AD.

(d) Within 6 months after the effective date of this AD, replace all Dunlop MLG wheels having part number AHA1752 Pre Mod 6, with MLG wheels having either part number AHA1752 Post Mod 6 or part number AHA1890. Such replacement constitutes terminating action for the requirements of this AD.

(e) 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, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Standardization Branch, ANM-113.

NOTE: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113.

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

(g) The inspections shall be done in accordance with Dunlop Limited, Aviation Division, Service Bulletin AHA1752-32-1069, dated June 28, 1993. 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 Dunlop Limited, Aviation Division, Silverton House, Vincent Square, London SW1P 2PL, United Kingdom. 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.

(h) This amendment becomes effective on June 6, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations to include an airworthiness directive (AD) that is applicable to certain Aerospatiale Model ATR72 series airplanes was published in the Federal Register on November 19, 1993 (58 FR 61038). That action proposed to require repetitive eddy current inspections to detect cracking in the bearing housing of the brake side half hub of Dunlop MLG wheels, part number AHA1752 Pre Mod 6. Additionally, that action proposed to require that, if any cracked half hub assemblies are detected, the complete wheel must be replaced. If certain improved replacement wheels are installed, the repetitive eddy current inspections may be discontinued. That action also proposed to require the eventual replacement of all MLG wheels having part number AHA1752 Pre Mod 6 with other (improved) wheels, as terminating action for the repetitive inspections.

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

The commenter supports the proposed rule.

After careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

The FAA estimates that 16 airplanes of U.S. registry will be affected by this AD, that it will take approximately 2 work hours per airplane to accomplish the required actions, and that the average labor rate is $55 per work hour. Based on these figures, the total cost impact of the inspection actions on U.S. operators is estimated to be $1,760, or $110 per airplane, per inspection. Should a cracked half hub assembly be found, replacement wheel assemblies will be provided by Dunlop at no charge to the operator.

The required wheel replacement action will require approximately 2 work hours to accomplish, at an average labor charge of $55 per work hour. Replacement parts will be provided by Dunlop at no charge to the operators, as part of Dunlop's repair/replacement program. Based on these figures, the total cost impact of the replacement actions on U.S. operators is estimated to be $1,760, or $110 per airplane.

The total 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 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 power and 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 14 CFR part 39 of the Federal Aviation Regulations as follows:
PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.
39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: