[Federal Register Volume 62, Number 164 (Monday, August 25, 1997)]
[Proposed Rules]
[Pages 44917-44919]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-22487]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-189-AD]
RIN 2120-AA64


Airworthiness Directives; British Aerospace BAe Model ATP 
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 British Aerospace BAe 
Model ATP airplanes. This proposal would require a detailed visual 
inspection of the flap drive torque tubes in the wing root area to 
detect inadequate clearance between the torque tubes and surrounding 
structure or scoring damage to the tubes; and follow-on repetitive 
inspections or corrective action, if necessary. Accomplishment of 
certain replacements and modifications would constitute terminating 
action for the repetitive inspections. This proposal is prompted by 
reports of inadequate clearance between flap drive torque tubes and 
surrounding structures, and possible scoring damage to the tubes. The 
actions specified by the proposed AD are intended to prevent failure of 
the torque tubes, which could result in an asymmetric flap condition 
and reduced controllability of the airplane.

DATES: Comments must be received by October 6, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-189-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 AI(R) American Support, Inc., 13850 Mclearen Road, 
Herndon, Virginia 20171. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: William Schroeder, Aerospace Engineer, 
Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
227-2148; fax (425) 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

[[Page 44918]]

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-189-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-189-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The Civil Aviation Authority (CAA), which is the airworthiness 
authority for the United Kingdom, notified the FAA that an unsafe 
condition may exist on certain British Aerospace BAe Model ATP 
airplanes. The CAA advises that, following reports of restrictions of 
flight control, a zonal survey was conducted of all flying control 
circuits on these airplanes. An area of reduced clearance, which was 
identified between the wing flap control system and wing center section 
structure, was found to affect the aluminum flap drive torque tubes. 
Such inadequate clearance and consequent scoring damage could lead to 
failure of the torque tubes, and result in an asymmetric flap condition 
and reduced controllability of the airplane.

Explanation of Relevant Service Information

    The manufacturer has issued Service Bulletin ATP-27-80, dated April 
23, 1996, which describes procedures for a detailed visual inspection 
of the flap drive torque tubes in the wing root area to detect 
inadequate clearance between the torque tubes and surrounding structure 
or scoring damage to the tubes; and follow-on repetitive inspections, 
if necessary. For certain cases, the service bulletin also describes 
procedures for the replacement of damaged torque tubes with new tubes 
and modification of the surrounding structure to gain adequate 
clearance. Accomplishment of such replacement and modification would 
eliminate the need for the repetitive inspections. The CAA classified 
this service bulletin as mandatory and issued British airworthiness 
directive 003-04-96 in order to assure the continued airworthiness of 
these airplanes in the United Kingdom.

FAA's Conclusions

    This airplane model is manufactured in the United Kingdom 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 CAA has kept the FAA 
informed of the situation described above. The FAA has examined the 
findings of the CAA, 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 require a detailed visual 
inspection of the flap drive torque tubes in the wing root area to 
detect inadequate clearance between the torque tubes and surrounding 
structure or scoring damage to the tubes; and follow-on repetitive 
inspections, if necessary. For certain cases, this proposal also would 
require the replacement of damaged torque tubes with new tubes and 
modification of the surrounding structure to gain adequate clearance. 
Accomplishment of the modification would constitute terminating action 
for the repetitive inspection requirement of this AD. These actions 
would be required to be accomplished in accordance with the service 
bulletin described previously.

Differences Between Proposed Rule and Service Bulletins

    Operators should note that Jetstream Service Bulletin ATP-27-80, 
dated April 23, 1996, differs from this AD in two respects:
    1. The service bulletin recommends that, if inadequate clearance 
exists between any flap drive torque tube and surrounding structure in 
the wing root area, and there is no scoring damage to the tubes, the 
detailed repetitive visual inspections of the tubes, at intervals not 
to exceed 250 hours time-in-service, may continue indefinitely. 
However, the proposed AD would require modification to achieve adequate 
clearance within 2,000 hours time-in-service after the initial 
inspection. 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.
    2. The service bulletin recommends that, if both torque tubes on 
the same side are damaged, and the scoring is within the maximum 
allowable damage limits specified, continued flight is allowed up to 
250 hours time-in-service before new torque tubes are installed. 
However, the proposed AD would require replacing at least one of the 
torque tubes with a new tube prior to further flight. The FAA has 
determined that failure of both torque tubes on one side during the 
same flight could result in an asymmetric flap condition and reduced 
controllability of the airplane. The FAA also has determined that if 
both torque tubes are damaged, even though the damage on either torque 
tube is within the allowable limits specified in the service bulletin 
during repetitive inspections, undetected residual damage could 
propagate unexpectedly and result in the failure of a torque tube. 
Therefore, considering the possible catastrophic results of an 
asymmetric flap condition, this proposed AD requires that at least one 
of the torque tubes on the same side remains undamaged at all times.

Cost Impact

    The FAA estimates that 10 British Aerospace BAe Model ATP airplanes 
of U.S. registry would be affected by this proposed AD, that it would 
take approximately 1 work hour per airplane to accomplish the proposed 
actions, and that the average labor rate is $60 per work hour. Based on 
these figures, the cost impact of the proposed AD on U.S. operators is 
estimated to be $600, or $60 per airplane.
    The cost impact figures discussed above are 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.

[[Page 44919]]

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), 40113, 44701.


Sec. 39.13  [Amended]

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

British Aerospace Regional Aircraft [Formerly Jetstream Aircraft 
Limited, ritish Aerospace (Commercial Aircraft) Limited]: Docket 96-
NM-189-AD.

    Applicability: BAe Model ATP airplanes, constructor numbers 2002 
through 2063 inclusive; 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 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 failure of the torque tubes, which could result in an 
asymmetric flap condition and reduced controllability of the 
airplane, accomplish the following:
    (a) Within 90 days after the effective date of this AD, conduct 
a detailed visual inspection of the flap drive torque tubes in the 
left and right wing root areas to detect inadequate clearance 
between the torque tubes and surrounding structure or scoring damage 
to the tubes, in accordance with Jetstream Service Bulletin ATP-27-
80, dated April 23, 1996.
    (1) If adequate clearance exists between all flap drive torque 
tubes and surrounding structure at the sites specified in the 
service bulletin, with no scoring damage to any of the tubes, no 
further action is required by this AD.
    (2) If inadequate clearance exists between any flap drive torque 
tube and surrounding structure at the sites specified in the service 
bulletin, with no scoring damage to the tubes: Accomplish the 
requirements of paragraphs (a)(2)(i) and (a)(2)(ii) of this AD.
    (i) At intervals not to exceed 250 hours time-in-service, repeat 
the detailed visual inspections required by paragraph (a) of this 
AD.
    (ii) Within 2,000 hours time-in-service after the initial 
inspection required by paragraph (a) of this AD, modify the 
structure to gain the required minimum clearance in accordance with 
the service bulletin. Accomplishment of the modification constitutes 
terminating action for the repetitive inspection requirement of 
paragraph (a)(2)(ii) of this AD.
    (3) If any scoring damage to the torque tubes is detected, 
accomplish the requirements specified in paragraph (a)(3)(i), 
(a)(3)(ii), or (a)(3)(iii) of this AD, as applicable, in accordance 
with the service bulletin, and at the time specified in the 
applicable paragraph.
    (i) If only one torque tube on one side or both sides of the 
airplane is damaged, and the scoring is within the maximum allowable 
damage limits in the service bulletin: Within 250 hours time-in-
service after any inspection required by this AD in which the damage 
was initially detected, modify the surrounding structure to gain the 
required minimum clearance and install a new torque tube.
    (ii) If both torque tubes on the same side of the airplane are 
damaged, and the scoring is within the maximum allowable damage 
limits in the service bulletin: Prior to further flight after any 
inspection required by this AD in which damage was initially 
detected, modify the surrounding structure to gain the required 
minimum clearance and replace at least one of the damaged torque 
tubes with a new torque tube. Within 250 hours time-in-service after 
any inspection in which damage was initially detected, replace the 
remaining damaged torque tube with a new torque tube.
    (iii) If any torque tube is damaged, and the scoring is more 
than the allowable damage limits described in the service bulletin: 
Prior to further flight, modify the surrounding structure to gain 
the required minimum clearance and replace the damaged tube(s) with 
a new torque tube(s).
    (b) Accomplishment of the modification to gain the required 
minimum clearance between the torque tubes and surrounding structure 
and the replacement of damaged torque tube(s) with a new torque 
tube(s) constitutes terminating action for the requirements of this 
AD.
    (c) An alternative method of compliance or adjustment of the 
initial 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 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 19, 1997.
S. R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-22487 Filed 8-22-97; 8:45 am]
BILLING CODE 4910-13-U