AD 98-21-10

This amendment adopts a new airworthiness directive (AD), applicable to certain Aerospatiale Model ATR42-200 and -300 series airplanes, that requires repetitive inspections for cracking of the lower skin panels of the outer wings; and repair, if necessary. This amendment also requires modification of the panels and a follow-on inspection to detect cracking of the modified areas, which constitute terminating action for the repetitive inspections. This amendment is prompted by the issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent fatigue cracking of the lower skin panels of the outer wings, and consequent reduced structural integrity of the airplane.

Final rule

98-21-10 AEROSPATIALE: Amendment 39-10818. Docket 97-NM-266-AD.

Applicability: Model ATR42-200 and -300 series airplanes on which Avions de Transport Regional Service Bulletins ATR42-57-0040, dated April 21, 1994, and ATR42-57-0038, Revision 2, dated December 18, 1997, have not been accomplished; except for those airplanes on which ATR Modification 2805 has been accomplished; certificated in any category.

NOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 repairon 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 fatigue cracking of the lower skin panels of the outer wings between ribs 13 and 18, and consequent reduced structural integrity of the airplane, accomplish the following:

(a) Prior to the accumulation of 25,500 total landings, or within 500 landings after the effective date of this AD, whichever occurs later, perform an ultrasonic inspection for cracking of the lower skin panels of the outer wings, in accordance with Avions de Transport Regional Service Bulletin ATR42-57-0040, dated April 21, 1994. If any crack is detected, prior to further flight, repair it in accordance with a method approved by the Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate. Thereafter, repeat the inspection at intervals not to exceed 9,000 landings.

(b) Prior to the accumulation of 32,500 total landings, or within 500 landings after the effective date of this AD, whichever occurs later, modify the lower skin panels of the outer wings, and perform a follow-on high frequency eddy current (HFEC) inspection for cracking of the modified areas, in accordance with Avions de Transport Regional Service Bulletin ATR42-57-0038, Revision 2, dated December 18, 1997. If any crack is detected, prior to further flight, repair it in accordance with a method approved by the Manager, International Branch, ANM-116. Accomplishment of the modification and follow-on HFEC inspection constitutes terminating action for the repetitive ultrasonic inspection requirements of paragraph (a) of this AD.

(c) 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, International Branch, ANM-116. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, International Branch, ANM-116.

NOTE 2: 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) Except for the repairs provided for in paragraphs (a) and (b) of this AD, the actions shall be done in accordance with the following Avions de Transport Regional Service Bulletins, which contain the specified list of effective pages:

Service Bulletin
Referenced and Date
Page Number
Shown on Page
Revision Level
Shown on Page
Date
Shown on Page
ATR42-57-0040,
April 21, 1994
1-15
Original
April 21, 1994
ATR42-57-0038,
Revision 2,
December 18, 1997
1-11, 21, 31-36
53, 55

18, 22, 27, 28, 37, 38,
51, 52, 56, 57

12-17, 19, 20, 23-26,
29, 30, 39-50, 54
2

1

Original
December 18, 1997

December 20, 1995

December 19, 1994

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 Aerospatiale, 316 Route de Bayonne, 31060 Toulouse, Cedex 03, France. 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 3: The subject of this AD is addressed in French airworthiness directive 93-190-051(B), dated October 27, 1993.

(f) This amendment becomes effective on November 12, 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 Aerospatiale Model ATR42-200 and -300 series airplanes was published in the Federal Register on February 10, 1998 (63 FR 6683). That action proposed to require repetitive inspections for cracking of the lower skin panels of the outer wings; repair, if necessary; modification of the panels; and a follow-on inspection to detect cracking of the modified areas, which would constitute 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 comments received.

Support for the Proposal
One commenter supports the proposed AD.

Request to Revise Applicability of the Proposal
One commenter, the manufacturer, requests that the applicability of the proposed AD be revised to exclude airplanes on which ATR Modification 2805 has been accomplished. The commenter states that this modification was developed to address cracking that was detected during full-scale fatigue testing and has been accomplished on certain airplanes during production. The commenter also points out that French airworthiness directive 93-190-051(B), which was referenced in the proposal as the parallel French airworthiness directive, excludes airplanes on which ATR Modification 2805 has been accomplished.

The FAA concurs with the commenter s request and has revised the applicability of the final rule to exclude airplanes on which ATR Modification 2805 has been accomplished.

Request to Revise Compliance Time
This same commenter expresses concern regarding the planned compliance time for the actions specified in the proposed AD. The commenter states that, for certain airplanes, the proposal allows a delay of 500 landings before the actions must be accomplished, and that sucha delay could allow those airplanes to exceed the thresholds specified in the French airworthiness directive. The commenter points out that those thresholds were defined according to a specific fatigue and damage tolerance analysis.

Although no specific request to change the final rule is made by the commenter in this regard, the FAA infers that the commenter is requesting that the FAA reduce or eliminate the grace period in the final rule. The FAA does not concur with the commenter s request and notes that the compliance times, as stated in the proposal, do indeed follow those specified by the French airworthiness directive. Specifically, the French airworthiness directive calls for accomplishment of the initial inspection prior to the accumulation of 26,000 total flights. Paragraph (a) of this final rule specifies that the initial inspection is to be accomplished prior to the accumulation of 25,500 total landings, or within 500 landings after the effective date of the AD, whichever occurs later.

Similarly, the French airworthiness directive calls for accomplishment of the modification prior to the accumulation of 33,000 total flights. Paragraph (b) of the final rule specifies that the modification is to be accomplished prior to the accumulation of 32,500 total landings, or within 500 landings after the effective date of this AD, whichever occurs later. The FAA considers that the grace period of 500 landings allows operators whose airplanes have exceeded the thresholds of 25,500 and 32,500 total landings adequate time to accomplish the inspections and modification, respectively, while adhering as closely as possible to the compliance times specified in the French airworthiness directive. No change to the final rule is necessary in this regard.

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 change described previously. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD.

Cost Impact
The FAA estimates that 101 airplanes of U.S. registry will be affected by this AD.

It will take approximately 4 work hours per airplane to accomplish the required ultrasonic inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the ultrasonic inspection required by this AD on U.S. operators is estimated to be $24,240, or $240 per airplane, per inspection cycle.

It will take approximately 280 work hours per airplane to accomplish the required modification, at an average labor rate of $60 per work hour. The cost of required parts will range from $1,576 to $6,373 per airplane. Based on these figures, the cost impact of the modification required by this AD on U.S. operators is estimated to be between $1,855,976 ($18,376 per airplane) and $2,340,473 ($23,173 per airplane).

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.

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: