AD 99-25-11

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 all British Aerospace Model BAe 146 series airplanes and certain British Aerospace Model Avro 146-RJ series airplanes was published in the Federal Register on June 28, 1999 (64 FR 34586). That action proposed to require repetitive eddy current inspections to detect fatigue cracking along the face of the retraction attachment boss in the nose landing gear sidewall; and corrective action, 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.

Request to Change the Statement of Unsafe Condition One commenter states that the description of the unsafe condition, as stated in the notice of proposed rulemaking (NPRM), is incorrect. The commenter requests that, instead of stating "suchfatigue cracking, if not corrected, could result in failure of the nose landing gear during take-off and landing," the consequence of such fatigue cracking should be stated as "premature extension of the nose landing gear and/or" depressurization of the aircraft."

The FAA concurs with the commenter s request. Therefore, the statement of unsafe condition has been revised in the summary and the body of the final rule to correctly state the unsafe condition.

Request to Allow Contact of Manufacturer if Cracks Are Found One commenter requests that the final rule be revised to state, "If cracks are found, before further flight[,] either[;] contact BAe Customer Support for further advice or repair in accordance with a method approved by the FAA." ; The commenter states that the proposed requirement for repair prior to further flight in accordance with a method approved by the FAA or Civil Aviation Authority (CAA), is too restrictive and could force operators to ground airplanes with cracks along the face of the retraction attachment boss in the nose landing gear sidewall, regardless of crack length. The commenter states that it has demonstrated by test that ultimate loads can be sustained if a crack has extended to the edge of the retraction attachment boss.

The FAA does not concur with the commenter s request. To require operators to contact the manufacturer for repair instructions, as suggested by the commenter, would be delegating the FAA s rulemaking authority to the manufacturer. In addition, because specific repair instructions were not included in the referenced service bulletin and have not been provided to the FAA by the manufacturer, the FAA cannot include specific repair instructions in the final rule. Also, although the manufacturer has advised that it plans to revise the service bulletin to include repair instructions, the FAA does not consider it appropriate to delay issuance of the final rule while awaiting the revised servicebulletin.

However, the FAA recognizes that the requirement to repair any crack prior to further flight, regardless of the length of the crack, could be, in this case, unnecessarily restrictive. As stated by the commenter, tests have shown that cracked structure within defined limits can sustain limit loads without failure. Thus, the FAA finds that a stringent repetitive inspection program, acceptable to the FAA or CAA, may provide an acceptable level of safety that would allow for deferment of a permanent repair for a certain period of time. Because the manufacturer has not provided the FAA with such a repetitive inspection program nor criteria to allow a temporary deferral of permanent repair, such instructions cannot be included in the final rule. However, to allow for the possibility of a temporary deferral of repair, paragraph (b) of this final rule has been revised to require, if any crack is detected, repair or reinspection prior to further flight in accordance witha method approved by the FAA or CAA.

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 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.

Cost Impact The FAA estimates that 44 airplanes of U.S. registry will be affected by this required AD, that it will take approximately 1 work hour per airplane to accomplish the required inspection, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the required AD on U.S. operators is estimated to be $2,640, or $60 per airplane, per inspection cycle.

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 accomplishthose 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 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: