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 Model BAe 146 and Model Avro 146-RJ series airplanes was published in the Federal Register on June 17, 1997 (62 FR 32701). That action proposed to require repetitive detailed visual inspections of the top wing skins for stress corrosion cracks, damage, or missing surface protective finish of the metallic surfaces, and repair, if necessary.
Consideration of Comments
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.
Components Made of 7150-T651 Aluminum Material
The commenter supports the proposed AD. However, the commenter expresses a concern that other airplane components made from the same material could pose a similar problem. As a result, the commenter requests the FAA to accomplish the following actions:
- Identify any other aircraft components made from the same material.
- Review the inspection criteria and frequency for those applications.
- Ensure that a failure of the material will be detected prior to the failure posing a risk to continued flight safety.
The FAA acknowledges the concerns of the commenter. Based on additional information from the manufacturer, the FAA has determined that the problem is limited to a discrepant production lot of 7150-T651 aluminum material that was produced with the incorrect thickness for the wing skins. In addition, the FAA has determined that no other components made of this aluminum material are affected. In light of this information, the FAA finds that it is unnecessary to take any additional action, and that the actions required by this AD are adequate in order to ensure the continued safety of the fleet.
Explanation of New Service Information
Since the issuance of the proposed AD, the manufacturer issued British Aerospace Service Bulletin SB.57-49, Revision 1, dated June 19, 1997, which replaces British Aerospace Service Bulletin SB.57-49, dated June 4, 1996. Revision 1 reduces the effectivity specified in the previous service bulletin to those airplanes on which 7150-T651 aluminum material from a discrepant production lot was used for the top wing skins. The discrepant material was manufactured with an inappropriate thickness, which causes the wings to be susceptible to early stress corrosion cracking on the top wing skin, and which could result in reduced structural integrity of the airplane wing. However, since the discovery of this problem, subsequent 7150-T651 aluminum material used for the top wing skins has been machined to the appropriate thickness and, as a result, is not susceptible to early stress corrosion cracking. In all other respects, Revision 1 of the service bulletin is essentially the same as the original issue of the service bulletin.
The FAA has reduced the applicability of this final rule to those airplanes having wing skins made from 7150-T651 aluminum material, as specified in British Aerospace Service Bulletin SB.57-49, Revision 1, dated June 19, 1997. In addition, the FAA has revised paragraph (a) of the final rule to require accomplishment of those actions in accordance with either the original service bulletin or Revision 1.
Conclusion
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 described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.
Cost Impact
The FAA estimates that 12 British Aerospace Model BAe 146 and Model Avro 146-RJ series airplanes of U.S. registry will be affected by this AD, that it will take approximately 4 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 $2,880, or $240 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 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 nota "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: