Airworthiness Directives; Aerospatiale Model ATR42-300 and ATR42- 320 Series Airplanes

[Federal Register Volume 62, Number 34 (Thursday, February 20, 1997)]
[Rules and Regulations]
[Pages 7665-7667]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-3843]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-24-AD; Amendment 39-9933; AD 97-04-09]
RIN 2120-AA64


Airworthiness Directives; Aerospatiale Model ATR42-300 and ATR42-
320 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Aerospatiale Model ATR42-300 and ATR42-320 
series airplanes. This action 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 ones and a follow-on inspection. This amendment is 
prompted by reports indicating that, due to fatigue cracking in the 
lower lugs of the barrel, the MLG collapsed. The actions specified in 
this AD are intended to detect and correct such fatigue cracking, which 
could lead to the collapse of the MLG.

DATES: Effective March 7, 1997.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of March 7, 1997.
    Comments for inclusion in the Rules Docket must be received on or 
before April 21, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 97-NM-24-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056.
    The service information referenced in this AD 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; or at the 
Office of the Federal Register, 800 North Capitol Street, NW., suite 
700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Gary Lium, Aerospace Engineer, 
Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 
227-1112; fax (206) 227-1149.

SUPPLEMENTARY INFORMATION: The Direction Generale de l'Aviation Civile 
(DGAC), which is the airworthiness authority for France, recently 
notified the FAA that an unsafe condition may exist on certain 
Aerospatiale Model ATR42-300 and ATR42-320 series airplanes. The DGAC 
advises that it has received reports indicating that the main landing 
gear (MLG) collapsed on two airplanes; one incident occurred during 
taxi and the other during landing roll. Investigation revealed that, 
following normal overhaul or repair procedures, moisture may enter the 
joint between the fixed barrel and the shock absorbing portion of the 
trailing arm of the MLG. Such moisture could result in corrosion and 
consequent fatigue cracking in the lower lugs of the barrel of the MLG, 
which is the main attachment point for the joint.
    Fatigue cracking in the lower lugs of the barrel of the MLG, if not 
detected and corrected in a timely manner, could lead to the collapse 
of the MLG.

Explanation of Relevant Service Information

    Messier-Dowty has issued Service Bulletin No. 631-32-132, dated 
January 21, 1997, which describes procedures for performing repetitive 
ultrasonic inspections to detect fatigue cracks of the barrel lower 
lugs of MLG. The service bulletin also describes procedures for 
replacement of cracked barrel lower lugs with new or serviceable ones 
and a follow-on inspection. The DGAC classified this service bulletin 
as mandatory and issued French airworthiness directive 96-294(B), dated 
January 15, 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 is being issued to detect and correct 
fatigue cracking in the lower lugs of the barrel, which could result in 
collapse of the MLG. This AD requires repetitive ultrasonic inspections 
to detect fatigue cracks of the lower lugs of the barrel of MLG. This 
AD also requires replacement of cracked lower lugs with new or 
serviceable ones and a follow-on inspection. The actions are required 
to be accomplished in accordance with the service bulletin described 
previously.

Interim Action

    The FAA is considering further rulemaking action to supersede this 
AD to require modification of the lower lugs of the barrel of the MLG, 
which will constitute terminating action for the repetitive inspections 
required by this AD action. However, the planned compliance time for 
these actions is sufficiently long so that prior notice and time for 
public comment will be practicable.

[[Page 7666]]

    In addition, the FAA is continuing to investigate whether the 
existing design of the lower lugs of the barrel makes overhauls or 
repairs difficult to accomplish correctly. Preliminary investigation 
results indicate that, following an improperly overhauled or repaired 
lower lug of the barrel, moisture could enter the joint between the 
fixed barrel and the shock absorbing portion of the trailing arm of the 
MLG. Such moisture could result in corrosion and consequent fatigue 
cracking in the lower lugs of the barrel, which may lead to the 
collapse of the MLG. Once final action is identified, the FAA may 
consider additional rulemaking.

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 comments will 
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-24-AD.'' The postcard will be 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.


Sec. 39.13   [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

97-04-09  Aerospatiale: Amendment 39-9933. Docket 97-NM-24-AD.

    Applicability: Model ATR42-300 and ATR42-320 series airplanes, 
on which the lower lugs of the barrel of the main landing gear (MLG) 
have been overhauled or repaired, certificated in any category.

    Note 1: This AD does not affect new barrel assemblies that have 
never been overhauled or repaired.
    Note 2: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
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 (b) 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 prevent fatigue cracking in the lower lugs of the barrel and 
consequent collapse of the MLG, accomplish the following:
    (a) Prior to the accumulation of 2 years time-in-service since 
last overhaul or repair of the barrel lower lugs of the MLG, or 
within 60 days after the effective date of this AD, whichever occurs 
later, 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.
    (1) If no echo is detected or the echo is less than 20%, repeat 
the ultrasonic inspection thereafter at intervals not to exceed 700 
landings.
    (2) If any echo is greater than or equal to 20%, prior to 
further flight, replace the barrel assembly with a new or 
serviceable barrel assembly, in accordance with the service 
bulletin. After replacement, prior to the accumulation of 2 years 
time-in-service on that replacement part, accomplish the actions 
specified in paragraph (a) of this AD.
    (b) 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, Standardization Branch, ANM-113, 
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, 
Standardization Branch, ANM-113.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Standardization Branch, ANM-113.

    (c) 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.
    (d) The inspections and replacement shall be done in accordance 
with Messier-Dowty Service Bulletin 631-32-132, dated January 21, 
1997. 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,

[[Page 7667]]

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.
    (e) This amendment becomes effective on March 7, 1997.

    Issued in Renton, Washington, on February 10, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-3843 Filed 2-19-97; 8:45 am]
BILLING CODE 4910-13-U

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