[Federal Register Volume 61, Number 170 (Friday, August 30, 1996)]
[Proposed Rules]
[Pages 45910-45912]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-22142]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-29-AD]
RIN 2120-AA64


Airworthiness Directives; Airbus Model A320 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Airbus Model A320 series 
airplanes. This proposal would require repetitive inspections to detect 
wear of the inboard flap trunnions, and modification or replacement, if 
necessary. This proposal would also require the eventual modification 
of the trunnions, which would terminate the repetitive inspections. 
This proposal is prompted by reports of wear damage found on the 
inboard flap drive trunnions that was caused by chafing of the Teflon 
rollers of the chain that actuates the sliding panel of the fairing. 
The actions specified by the proposed AD are intended to prevent such 
chafing and resultant wear damage, which could result in the failure of 
the trunnion primary load path; this would adversely affect the fatigue 
life of the secondary load path and could lead to loss of the flap.

DATES: Comments must be received by October 8, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-29-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 Airbus Industrie, 1 Rond Point Maurice Bellonte, 31707 
Blagnac Cedex, France. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: Tim Backman, Aerospace Engineer, 
Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 
227-2797; fax (206) 227-1149.

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 notice 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 notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 96-NM-29-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-103, Attention: Rules 
Docket No. 96-NM-29-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    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 Airbus Model A320 series 
airplanes. The DGAC advises that several operators have found wear 
marks on the inboard drive flap trunnions (both left-hand and right-
hand) during removal and inspection of the inboard flaps. Investigation 
has revealed that such wear is caused by chafing of the Teflon rollers 
of the drive chain that actuates the sliding panel on the track No. 1 
fairing. This chafing and resultant wear damage, if not corrected, 
could result in the failure of the trunnion primary load path. This 
failure would adversely affect the fatigue life of the secondary load 
path and, consequently, could lead to the loss of the flap.

Explanation of Relevant Service Information

    Airbus has issued Service Bulletin A320-27-1066, dated March 7, 
1994; and Revision 1, dated February 21, 1995. These service bulletins 
describe a program for conducting repetitive inspections to detect wear 
damage of the inboard flap trunnions. The interval for conducting each 
inspection depends

[[Page 45911]]

upon the amount of wear detected during the last inspection. These 
inspections are intended to detect wear marks in the outside diameter 
(primary load path) of the trunnion before they reach a critical depth 
that would lead to failure. If wear damage exceeds a certain amount, 
the service bulletin recommends that the trunnions be modified in 
accordance with the procedures specified in Airbus Service Bulletin 
A320-27-1050. Additionally, if wear damage is great (more than 5.0 mm 
in depth), the service bulletin recommends that Airbus be contacted for 
further actions. The DGAC classified this service bulletin as mandatory 
and issued French airworthiness directive (CN) 94-165-055(B), dated 
July 30, 1994, in order to assure the continued airworthiness of these 
airplanes in France.
    Additionally, Airbus has issued Service Bulletin A320-27-1050, 
Revision 3, dated October 21, 1994, which describes procedures for 
modifying the inboard flap drive trunnions. The modification is 
identified as Modification 22881, and entails installing protective 
half shells on the trunnion assembly to prevent chafing and wear 
damage. Once this modification is accomplished, the repetitive 
inspections of the trunnions to detect wear marks are no longer 
necessary. The DGAC has approved the technical content of this service 
bulletin and has classified it as ``recommended.''

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 the 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 require repetitive 
inspections to detect wear of each inboard flap trunnion. It would also 
require that the trunnion be either modified or replaced, depending 
upon the amount of wear detected.
    This proposed AD also would require that Modification 22881 be 
installed eventually on trunnions of all affected airplanes as 
terminating action for the repetitive inspections.
    The inspection, modification, and replacement actions would be 
required to be accomplished in accordance with the service bulletins 
described previously.

Differences Between Proposed Rule and Service Information

    The inboard flap attachment trunnion is a primary structural 
element that is designed with both a primary and a secondary load path. 
The wear marks that have been found have been located on the outside 
diameter of the trunnion, which is the primary load path. Modification 
22881, described in Airbus Service Bulletin A320-27-1050, entails 
installing protective half-shells on this outside diameter to prevent 
further wear damage.
    Unlike the Airbus service bulletin and the French CN, this proposed 
AD would require the installation of Modification 22881as terminating 
action for the repetitive inspections. The FAA has determined that long 
term continued operational safety will be better assured by 
modifications or design changes to remove the source of the problem, 
rather than by repetitive inspections. Long term inspections may not be 
providing the degree of safety assurance necessary for the transport 
airplane fleet. This, coupled with a better understanding of the human 
factors associated with numerous repetitive inspections, has led the 
FAA to consider placing less emphasis on special procedures and more 
emphasis on design improvements. The proposed modification requirement 
is in consonance with these considerations.

Cost Impact

    The FAA estimates that 91 airplanes of U.S. registry would be 
affected by this proposed AD.
    Accomplishment of the proposed inspections would take approximately 
3 work hours per airplane, at an average labor rate of $60 per work 
hour. (This includes the time necessary to gain access, inspect, and 
close up.) Based on these figures, the cost impact of the proposed 
inspection requirement on U.S. operators is estimated to be $16,380, or 
$180 per airplane, per inspection.
    Accomplishment of the proposed modification would require 
approximately 93 work hours, at an average labor rate of $60 per work 
hour. (This includes the time necessary to gain access, modify, test, 
and close up.) Required parts would cost approximately $1,923 per 
airplane. Based on these figures, the cost impact of the proposed 
modification requirement on U.S. operators is estimated to be $682,773, 
or $7,502 per airplane.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the 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 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    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), 40101, 40113, 44701.

[[Page 45912]]

Sec. 39.13  [Amended]

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

Airbus: Docket 96-NM-29-AD.

    Applicability: Model A320-111, -211, -212, -231, and -232 series 
airplanes; as listed in Airbus Service Bulletin A320-27-1066, 
Revision 1, dated February 21, 1995; and on which Airbus 
Modification 22881 has not been installed; certificated in any 
category.

    Note 1: 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 (c) 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 chafing and resultant wear damage to the inboard flap 
trunnion, which could result in the failure of the trunnion primary 
load path, could adversely affect the fatigue life of the secondary 
load path, and could lead to loss of the flap, accomplish the 
following:
    (a) Prior to the accumulation of 500 flight hours after the 
effective date of this AD, conduct a detailed visual inspection to 
detect wear marks on each inboard flap trunnion (right-hand and 
left-hand), in accordance with Airbus Service Bulletin A320-27-1066, 
dated March 7, 1994, or Revision 1, dated February 21, 1995. Measure 
and record the depth of all wear marks found on each trunnion, in 
accordance with the service bulletin.
    (1) If no wear marks are found or if the depth of the deepest 
wear mark is less than or equal to 2.0 mm: Repeat the inspection at 
intervals not to exceed 5,000 flight hours.
    (2) If the depth of the deepest wear mark is greater 2.0 mm but 
less than or equal to 3.0 mm: Repeat the inspection within the next 
1,000 flight hours. Prior to the accumulation of 5,000 flight hours 
after the initial inspection, modify the trunnion (Modification 
22881) in accordance with Airbus Service Bulletin A320-27-1050, 
Revision 3, dated October 21, 1994. This modification constitutes 
terminating action for the repetitive inspections of that trunnion 
required by this AD.
    (3) If the depth of the deepest wear mark is greater 3.0 mm, but 
is less than or equal to 4.0 mm: Prior to the accumulation of 500 
flight hours after the initial inspection, modify the trunnion 
(Modification 22881) in accordance with Airbus Service Bulletin 
A320-27-1050, Revision 3, dated October 21, 1994. This modification 
constitutes terminating action for the repetitive inspections of 
that trunnion that are required by this AD.
    (4) If the deepest wear mark exceeds 4.0 mm: Prior to further 
flight, replace the trunnion in accordance with the Airbus Model 
A320 Maintenance Manual. This replacement constitutes terminating 
action for the repetitive inspections of that trunnion that are 
required by this AD.
    (b) Prior to the accumulation of 10,000 total flight hours, 
modify each inboard flap trunnion, right-hand and left-hand, 
(Modification 22881) in accordance with Airbus Service Bulletin 
A320-27-1050, Revision 3, dated October 21, 1994. Accomplishment of 
this modification on each trunnion constitutes terminating action 
for the inspections required by 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, Standardization Branch, ANM-113. 
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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Standardization Branch, ANM-113.

    (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.

    Issued in Renton, Washington, on August 23, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-22142 Filed 8-29-96; 8:45 am]
BILLING CODE 4910-13-P