AD 97-26-19

This amendment supersedes an existing airworthiness directive (AD), applicable to all Aerospatiale Model ATR42-300 and ATR42-320 series airplanes, that currently requires repetitive ultrasonic inspections to detect fatigue cracks of the lower lugs of the barrel of the main landing gear (MLG); and replacement of cracked lower lugs with new or serviceable parts, and a follow-on inspection. This amendment expands the applicability of the existing AD. This action also provides for an optional terminating action, which, if accomplished, terminates the repetitive inspection requirement. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified in this AD are intended to detect and correct fatigue cracking of the lower lugs of the barrel of the MLG, which could lead to the collapse of the MLG.

Final rule; request for comments.

97-26-19 AEROSPATIALE: Amendment 39-10262. Docket 97-NM-283-AD. Supersedes AD 97-04-09, Amendment 39-9933.

Applicability: All Model ATR42-300 and ATR42-320 series airplanes, 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 (e) 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 and correct fatigue cracking in the lower lugs of the barrel of the main landing gear (MLG), and consequent collapse of the MLG, accomplish the following:

(a) Perform an ultrasonic inspection to detect fatigue cracks of the lower lugs of the barrel of the MLG, in accordance with Messier-Dowty Service Bulletin 631-32-132, dated January 21, 1997, at the time specified in paragraph (a)(1) or (a)(2) of this AD, as applicable:

(1) Within 2 years after the last overhaul or repair of the lower lugs of the barrel of the MLG, or within 60 days after March 7, 1997 (the effective date of AD 97-04-09, amendment 39-9933), whichever occurs later; or

(2) Within 5 years after the installation of a new MLG barrel assembly, or within 60 days after the effective date of this AD, whichever occurs later.

(b) If, during any inspection required by this AD, no echo is detected, or if the echo is less than 20%, repeat the ultrasonic inspection thereafter at intervals not to exceed 900 landings.

(c) If, during any inspection required by this AD, the echo is greater than or equal to 20%, prior to further flight, replace the MLG barrel assembly with a new or serviceable MLG barrel assembly, in accordance with the service bulletin.

(1) If the damaged barrel assembly is replaced with an overhauled or repaired assembly, within 2 years after installation of that overhauled or repaired part, accomplish the actions specified in paragraph (a) of this AD.

(2) If the damaged barrel assembly is replaced with a new barrel assembly, within 5 years after installation of that new part, accomplish the actions specified in paragraph (a) of this AD.

(d) Modification of the lower lugs of the barrel of the MLG in accordance with Messier-Dowty Service Bulletin 631-32-133, dated February 24, 1997, as revised by Messier- Dowty Service Bulletin Change Notice No. 1, dated March 18, 1997, constitutes terminating action forthe repetitive inspection 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, International Branch, ANM-116, 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, 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.

(f) 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.

(g) The actions shall be done in accordance with Messier-Dowty Service Bulletin 631- 32-133, dated February 24, 1997, as revised by Messier-Dowty Service Bulletin Change Notice No. 1, dated March 18, 1997; and Messier-Dowty Service Bulletin 631-32-132, dated January 21, 1997.

(1) The incorporation by reference of Messier-Dowty Service Bulletin 631-32-133, dated February 24, 1997, as revised by Messier-Dowty Service Bulletin Change Notice No. 1, dated March 18, 1997, is approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51.

(2) The incorporation by reference of Messier-Dowty Service Bulletin 631-32-132, dated January 21, 1997, was approved previously by the Director of the Federal Register as of March 7, 1997 (62 FR 7665, February 20, 1997).

(3) 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 96- 294(B)R1, dated September 10, 1997.

(h) This amendment becomes effective on January 7, 1998.

On February 10, 1997, the FAA issued AD 97-04-09, amendment 39-9933 (62 FR 7665, February 20, 1997), which is applicable to certain Aerospatiale Model ATR42-300 and ATR42-320 series airplanes. That AD requires repetitive ultrasonic inspections to detect fatigue cracks of the lower lugs of the barrel of the main landing gear (MLG), for airplanes on which the barrel assembly has been overhauled or repaired. If any lower lug is found to be cracked, the AD further requires replacement of the MLG barrel assembly with new or serviceable parts, and a follow-on inspection. That action was prompted by reports indicating that, due to fatigue cracking in the lower lugs of the barrel, the MLG collapsed. The actions required by that AD are intended to detect and correct such fatigue cracking, which could lead to the collapse of the MLG.

Actions Since Issuance of Previous Rule
Since the issuance of that AD, the Direction G n rale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, advises that further investigation has revealed that the fatigue cracking is the result of a design flaw that may also affect new barrel assemblies that have never been overhauled or repaired. In addition, the DGAC advises that the interval for the repetitive inspections may be extended from 700 landings to 900 landings.

Relevant Service Information
Messier-Dowty has issued Service Bulletin 631-32-133, dated February 24, 1997, which describes procedures to modify the lower lugs of the barrel of the MLG. The modification entails reconditioning the lower lugs and installing new bushings on the swinging lever. Accomplishment of this modification will prevent failure of the lugs due to fatigue cracking. Accomplishment of the modification eliminates the need for the repetitive visual inspections. The DGAC classified this service bulletin as mandatory, and issued French airworthiness directive 96-294(B)R1, dated September 10, 1997, in order to assure the continued airworthiness of these airplanes in France.

FAA's Conclusions
This airplane model is manufactured in France and is type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the DGAC has kept the FAA informed of the situation described above. The FAA has examined the findings of the DGAC, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.

Explanation of Requirements of Rule
Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, this AD supersedes AD 97-04-09 to continue to require repetitive ultrasonic inspections to detect fatigue cracks of thelower lugs of the barrel of the main landing gear (MLG); and replacement of cracked lower lugs with new or serviceable parts, and a follow-on inspection. This AD expands the applicability of the existing AD to include all Model ATR42-300 and -320 series airplanes, regardless of whether the MLG barrel assemblies installed on those airplanes are new, overhauled, or repaired. Additionally, this AD extends the repetitive inspection interval from 700 to 900 landings.

This AD also provides for optional modification of the lower lugs of the barrel of the MLG, which, if accomplished, constitutes terminating action for the repetitive inspection requirements of this AD. The modification is required to be accomplished in accordance with the service bulletin described previously.

Interim Action
This is considered to be interim action. The FAA is currently considering requiring the modification of the lower lugs of the barrel of the MLG. However, the planned compliance time for the installation of the modification is sufficiently long so that prior notice and time for public comment will be practicable.

Determination of Rule's Effective Date
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.

Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for commentswill be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 97-NM-283-AD." The postcard willbe date stamped and returned to the commenter.

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.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, 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 removing amendment 39-9933 (62 FR 7665, February 20, 1997), and by adding a new airworthiness directive (AD), amendment 39-10262, to read as follows: