00-30122. Airworthiness Directives; Aerospatiale Model ATR42-200, -300, and -320 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to all Aerospatiale Model ATR42-300 and -320 series airplanes. The existing AD requires repetitive ultrasonic inspections to detect cracking of certain lugs on the main landing gear (MLG), replacement of cracked lugs with new or serviceable parts, and a follow-on inspection; and provides for an optional terminating action for the repetitive inspections. This action would remove that terminating action and require new repetitive inspections of the rubber sealant to detect shearing, and corrective action, if necessary. This action also would require new one-time visual and fluorescent penetrant inspections to detect discrepancies of certain lugs and refurbishment of the MLG barrel and swing lever assemblies, which would terminate the requirements of this proposed AD. This action would also revise the applicability of the existing AD. This proposal is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by the proposed AD are intended to detect and correct discrepancies of the MLG barrel lower lugs, which could result in reduced structural integrity and possible collapse of the MLG.

DATES:

Comments must be received by December 28, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-139-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays.

The service information referenced in the proposed rule may be obtained from Aerospatiale, 316 Route de Bayonne, 31060 Toulouse, Cedex 03, France. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Norman B. Martenson, Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed 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 above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 98-NM-139-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-139-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On December 15, 1997, the FAA issued AD 97-26-19, amendment 39-10262 (62 FR 66980, December 23, 1997), applicable to all Aerospatiale Model ATR42-300 and -320 series airplanes, to require 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. The existing AD further provides for an optional terminating action for the repetitive inspections. That action was prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The requirements of that AD are intended to detect and correct fatigue cracking of the lower lugs of the barrel of the MLG, which could lead to collapse of the MLG.

Actions Since Issuance of Previous Rule

Since the issuance of that AD, the Direction Generale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, has advised the FAA of cases of rotation of the MLG bushings at the swinging lever hinge. This rotation damaged the anticorrosion protection of the MLG barrel. These cases occurred on airplanes on which the optional terminating action provided in the existing AD had been accomplished. Corrosion of the MLG barrel, if not corrected, could result in reduced structural integrity and possible collapse of the MLG.

Explanation of Relevant Service Information

Messier-Dowty (the manufacturer of landing gears installed on Model ATR42 series airplanes) has issued Service Bulletin 631-32-144, dated January 19, 1998, which describes procedures for repetitive visual inspections of the rubber sealant around the bushings at the MLG barrel and swinging lever hinge point to detect discrepancies (including shearing or separation). Corrective actions for discrepancies include repeating the actions (including an ultrasonic inspection to detect fatigue cracks of the lower lugs of the MLG barrel, and, if necessary, replacement of the MLG barrel assembly with a new or serviceable MLG barrel assembly) specified by Messier-Dowty Service Bulletin 631-32-132, dated January 21, 1997.

Messier-Dowty has also issued Service Bulletin 631-32-145, dated February 16, 1998, which describes procedures for one-time detailed visual and fluorescent penetrant inspections of the MLG barrel lower lugs; and refurbishment of the barrel lower lug and swinging lever assemblies, including restoration of the protective coating, replacement of the old bushings with new bushings, and installation of lubrication fittings. This service bulletin replaces Messier-Dowty Service Bulletin 631-32-133 (which the existing AD refers to for accomplishment of the optional terminating action).

Accomplishment of the actions specified by the service bulletins is intended to adequately address the identified unsafe condition. The DGAC classified these service bulletins as mandatory and issued French airworthiness directive 1996-294(B) R4, dated March 10, 1999, in order to ensure the continued airworthiness of these airplanes in France.

FAA's Conclusions

These airplane models are manufactured in France and are 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 Proposed 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, the proposed AD would supersede AD 97-26-19 to:

• Continue to require repetitive ultrasonic inspections to detect fatigue cracks of the lower lugs of the MLG barrel, replacement of cracked lower lugs with new or serviceable parts, and a follow-on inspection;
• Require new one-time visual and fluorescent penetrant inspections to detect discrepancies of certain lugs, and refurbishment of the MLG barrel and swing lever assemblies; which would terminate the repetitive inspections;
• Reduce the repetitive interval for the ultrasonic inspection for certain airplanes;
• Revise the applicability to include Model ATR42-200 series airplanes, which have been determined to be subject to the identified unsafe condition;
• Revise the applicability to exclude airplanes that have been refurbished in accordance with Messier-Dowty Service Bulletin 631-32-145; and
• Require operators to report results of inspection findings to Messier-Dowty.

The actions would be required to be accomplished in accordance with the service bulletins described previously, except as discussed below.

Differences Between Proposed AD and French Airworthiness Directive

The proposed AD would require an inspection of the rubber sealant around the bushings at the MLG barrel and swinging lever point within 400 flight hours; the parallel French airworthiness directive recommends accomplishment of the inspection prior to the next “A” check. In developing an appropriate compliance time for this proposed AD, the FAA considered the minimum maintenance intervals recommended by the Maintenance Review Board, the DGAC's recommendation, the degree of urgency associated with addressing the subject unsafe condition, and the average utilization of the affected fleet. Further, because maintenance schedules, including “A” checks, may vary from operator to operator, there would be no assurance that the actions would be accomplished within the proposed compliance time. In light of these factors, the FAA finds that the compliance time of 400 flight hours, as proposed, represents the maximum interval of time allowable for the affected airplanes to continue to operate prior to accomplishing the proposed actions without compromising safety.

Operators should note that, unlike the procedures described in Messier-Dowty Service Bulletin 631-32-144, this proposed AD would not permit further flight with discrepant sealant. The FAA has determined that, because of the safety implications and consequences associated with such discrepancies, any subject sealant that is found to be discrepant must be repaired or modified prior to further flight.

Operators should note that, although Messier-Dowty Service Bulletin 631-32-145 specifies that the manufacturer may be contacted for disposition of certain repair conditions, this proposal would require either replacing the discrepant MLG barrel, or repairing the discrepant part in accordance with a method approved by the FAA or the DGAC (or its delegated agent). In light of the type of repair that would be required to address the identified unsafe condition, and in consonance with existing bilateral airworthiness agreements, the FAA has determined that, for this proposed AD, a repair approved by either the FAA or the DGAC would be acceptable for compliance with this proposed AD.

Cost Impact

There are approximately 84 airplanes of U.S. registry that would be affected by this proposed AD.

The inspection that is currently required by AD 97-26-19, and retained in this proposed AD, takes approximately 2 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required actions on U.S. operators is estimated to be $120 per airplane, per inspection cycle.

The new inspections and refurbishment that are proposed in this AD action would take approximately 29 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Required parts would cost approximately $4,822 per airplane. Based on these figures, the cost impact of the proposed requirements of this AD on U.S. operators is estimated to be $551,208, or $6,562 per airplane.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or proposed 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 proposed herein would not have a substantial direct effect 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, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this proposed regulation (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, 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 copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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 39-10262 (62 FR 66980, December 23, 1997), and by adding a new airworthiness directive (AD), to read as follows:

Aerospatiale: Docket 98-NM-139-AD. Supersedes AD 97-26-19, Amendment 39-10262.

Applicability: Model ATR42-200, -300, and -320 series airplanes; certificated in any category; except airplanes that have been refurbished in accordance with Messier-Dowty Service Bulletin 631-32-145, dated February 16, 1998.

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 (k)(1) 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 discrepancies of the main landing gear (MLG) barrel lower lugs, which could result in reduced structural integrity and possible collapse of the MLG, accomplish the following:

Ultrasonic Inspection

(a) For airplanes on which the actions specified by Messier-Dowty Service Bulletin 631-32-133, dated February 24, 1997, as revised by Change Notice No. 1, dated March 18, 1997, have not been accomplished prior to the effective date of this AD: 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 applicable time specified in paragraph (a)(1), (a)(2), (a)(3), or (a)(4) of this AD.

(1) For Model ATR42-300 and -320 series airplanes: Inspect 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.

(2) For Model ATR42-300 and -320 series airplanes: Inspect within 5 years after the installation of a new MLG barrel assembly, or within 60 days after January 7, 1998 (the effective date of AD 97-26-19, amendment 39-10262); whichever occurs later.

(3) For Model ATR42-200 series airplanes: Inspect within 2 years after the last overhaul or repair of the lower lugs of the barrel of the MLG, or within 60 days after the effective date of this AD, whichever occurs later.

(4) For Model ATR42-200 series airplanes: Inspect 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 specified in paragraph (a) of this AD, no ultrasonic echo (as described in Messier-Dowty Service Bulletin 631-32-133, dated February 24, 1997, as revised by Change Notice No. 1, dated March 18, 1997) is detected, or if the echo is less than 20%: Except as required by paragraph (c) of this AD, repeat the ultrasonic inspection thereafter at intervals not to exceed 900 landings.

(c) For airplanes that are subject to the repetitive inspection requirements of paragraph (b) of this AD: As of the effective date of this AD, repeat the inspection, as specified by Table 1 of this AD, until the requirements of paragraph (f) of this AD are accomplished. Table 1 is as follows:

Table 1.—Repetitive Interval

If the first ultrasonic inspection specified by paragraph (a) of this AD was done . . .	Then repeat the ultrasonic inspection . . .
(1) At least 24 months, and less than 42 months, before the effective date of this AD	Within 500 landings after the first ultrasonic inspection, or within 60 days after the effective date of this AD, whichever occurs later; and thereafter at intervals not to exceed 500 landings.
(2) Less than 24 months before the effective date of this AD, or at any time on or after the effective date of this AD	At intervals not to exceed 900 landings, for a period not to exceed 24 months after the first ultrasonic inspection of (a) of this AD; and thereafter at intervals not to exceed 500 landings.

(d) If, during any inspection specified in paragraph (a) of 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 Messier-Dowty Service Bulletin 631-32-132, dated January 21, 1997.

(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.

Inspection of Sealant

(e) For airplanes on which the actions specified by Messier-Dowty Service

Bulletin 631-32-133, dated February 24, 1997, as revised by Change Notice No. 1, dated March 18, 1997, have been accomplished prior to the effective date of this AD: Within 400 flight hours after the effective date of this AD, perform a detailed visual inspection to detect discrepancies (including shearing or separation) of the rubber sealant between the bushings and the MLG barrel lower lugs, and between the bushing and the swinging lever lug, in accordance with Messier-Dowty Service Bulletin 631-32-144, dated January 19, 1998. Repeat the inspection thereafter at intervals not to exceed 400 flight hours, until accomplishment of the actions required by paragraph (f) of this AD.

Note 2:

For the purposes of this AD, a detailed visual inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”

(1) If no discrepancy is detected, repeat the detailed visual inspection specified in paragraph (e) of this AD thereafter at intervals not to exceed 300 landings, until accomplishment of the actions required by paragraph (f) of this AD.

(2) If any discrepancy is detected, prior to further flight, repeat the ultrasonic inspection and all applicable corrective actions specified by paragraphs (a), (b), and (d) of this AD.

Inspections and MLG Refurbishment

(f) For all airplanes: At the applicable time specified by paragraph (g) or (h) of this AD, accomplish the actions required by paragraphs (f)(1) and (f)(2) of this AD, in accordance with Messier-Dowty Service Bulletin 631-32-145, dated February 16, 1998, or Revision 1, dated May 31, 1999. Accomplishment of the inspections and refurbishment required by this paragraph constitutes terminating action for the requirements of this AD.

(1) Perform a one-time detailed visual inspection and a one-time fluorescent penetrant inspection to detect discrepancies (cracks, corrosion, and material defects) of the barrel lower lugs (outboard and inboard).

(i) If no discrepancy is found, prior to further flight, refurbish the lugs in accordance with the service bulletin.

(ii) If any discrepancy is found, prior to further flight, refurbish the lugs in accordance with the service bulletin and repeat the detailed visual inspection and fluorescent penetrant inspection. If any discrepancy remains, prior to further flight, do the actions specified by either paragraph (f)(1)(ii)(A) or (f)(1)(ii)(B) of this AD.

(A) Replace the damaged MLG barrel with a new or reconditioned barrel.

(B) Repair in accordance with a method approved by either the Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate; or the Direction Generale de l'Aviation Civile (DGAC) (or its delegated agent). For a repair method to be approved by the Manager, International Branch, ANM-116, as required by this paragraph, the Manager's approval letter must specifically reference this AD.

(2) Refurbish the MLG (including restoring the protective treatments, installing new bushings, and installing new lubrication points of the MLG barrel and swinging lever assemblies).

Compliance Times for Inspections and Refurbishment

(g) For airplanes on which the actions specified by Messier-Dowty Service Bulletin 631-32-133, dated February 24, 1997, have not been accomplished prior to the effective date of this AD: Do the actions required by paragraph (f) of this AD at the earlier of the times specified by paragraphs (g)(1) and (g)(2) of this AD.

(1) At the next overhaul of the MLG leg, not to exceed 42 months after the effective date of this AD.

(2) Within 42 months after the first ultrasonic inspection in accordance with paragraph (a) of this AD, or within 60 days after the effective date of this AD, whichever occurs later.

(h) For airplanes on which the actions specified by Messier-Dowty Service Bulletin 631-32-133, dated February 24, 1997, have been accomplished prior the effective date of this AD: Do the actions required by paragraph (f) of this AD within 24 months after the initial sealant inspection required by paragraph (e) of this AD.

Reporting Requirement

(i) At the applicable time specified by paragraph (i)(1) or (i)(2) of this AD, submit a report of the results (both positive and negative findings) of the initial inspections required by paragraphs (a) and (e) of this AD to Messier-Dowty, BP 10-78142 Velizy Cedex, France. Information collection requirements contained in this regulation have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120-0056.

(1) For airplanes on which the inspections are accomplished after the effective date of this AD: Submit a report of each inspection within 10 days after performing the applicable inspection.

(2) For airplanes on which the inspections have been accomplished prior to the effective date of this AD: Submit the report within 10 days after the effective date of this AD.

Spares

(j) As of the effective date of this AD, no person shall install a bushing, part number D66349, on the MLG barrel and swinging lever assemblies on any airplane.

Alternative Methods of Compliance

(k)(1) 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-114.

(2) Alternative methods of compliance approved previously in accordance with AD 97-26-19, amendment 39-10262, are approved as alternative methods of compliance with this AD.

Note 3:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the International Branch, ANM-116.

Special Flight Permits

(l) 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.

Note 4:

The subject of this AD is addressed in French airworthiness directive 1996-294(B) R4, dated March 10, 1999.

Issued in Renton, Washington, on November 20, 2000.

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.