[Federal Register Volume 59, Number 67 (Thursday, April 7, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-8326]
[[Page Unknown]]
[Federal Register: April 7, 1994]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-06-AD]
Airworthiness Directives; de Havilland Model DHC-8-100 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 de Havilland Model DHC-8-
100 series airplanes. This proposal would require modification of the
potentiometer lever stops on the nose wheel steering. This proposal is
prompted by a report that the potentiometer stops installed currently
on these airplanes are too short to limit excessive uncontrolled
potentiometer movement in the event of a mechanical link failure. The
actions specified by the proposed AD are intended to prevent the
airplane from departing the runway during takeoff or landing in the
event of the failure of the mechanical link between the rudder pedals
and the potentiometer.
DATES: Comments must be received by June 1, 1994.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 94-NM-06-AD, 1601 Lind Avenue SW., Renton,
Washington 98055-4056. Comments may be inspected at this location
between 9 a.m. and 3 p.m., Monday through Friday, except Federal
holidays.
The service information referenced in the proposed rule may be
obtained from Bombardier Inc., Bombardier Regional Aircraft Division,
Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. This information
may be examined at the FAA, Transport Airplane Directorate, 1601 Lind
Avenue, SW., Renton, Washington; or at the FAA, Engine and Propeller
Directorate, New York Aircraft Certification Office, 181 South Franklin
Avenue, Valley Stream, New York.
FOR FURTHER INFORMATION CONTACT: Bradford Chin, Electronics Engineer,
Systems and Equipment Branch, ANE-173, FAA, Engine and Propeller
Directorate, New York Aircraft Certification Office, 181 South Franklin
Avenue, room 202, Valley Stream, New York 11581; telephone (516) 791-
6427; fax (516) 791-9024.
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 94-NM-06-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. 94-NM-06-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
Transport Canada Aviation, which is the airworthiness authority for
Canada, recently notified the FAA that an unsafe condition may exist on
certain de Havilland Model DHC-8-100 series airplanes. Transport Canada
Aviation advises that when a Model DHC-8 series airplane is in the high
speed taxi mode during takeoff or landing, nose gear steering is
limited to 7 degrees left or right of center and is controlled through
rudder pedal movement. Rotary movement of the rudder input quadrant is
transmitted to a dual potentiometer via a mechanical link and fork
lever. The potentiometer converts this movement into electrical
signals, which are sent to an electronic control unit (ECU) located in
the nose of the airplane. Subsequently, the ECU signals the electro-
hydraulic actuator on the nose gear, thereby rotating the nose gear in
the required direction.
If the mechanical link connecting the potentiometer to the rudder
input quadrant fails, excessive uncontrolled potentiometer lever
movement is restricted by small metal stops located outside the normal
angular travel of the fork lever. These ``potentiometer stops'' limit
the size of the signal sent to the ECU only in the event of a
mechanical link failure. On certain Model DHC-8-100 series airplanes,
the currently installed potentiometer stops are too short to restrict
excessive fork lever movement in the event of a mechanical link
failure. In this case, a signal that is too large would be sent to the
ECU, which could cause the nose gear to exceed its 7-degree limitation.
This condition, if not corrected, could result in the airplane
departing the runway during takeoff or landing.
Bombardier Inc. has issued de Havilland Service Bulletin S.B. 8-32-
99, Revision `A,' dated July 26, 1993, that describes procedures for
modification of the potentiometer lever stops on the nose wheel
steering (Modification 8/1809) on certain Model DHC-8-100 and -300
series airplanes. Accomplishment of this modification will restore
overtravel protection by relocating the potentiometer lever stops.
Relocation of the stops will ensure that excessive fork lever movement
is restricted in the event of a mechanical link failure. Transport
Canada Aviation classified this service bulletin as mandatory and
issued Canadian Airworthiness Directive (AD) No. CF-93-24, dated
September 29, 1993, in order to assure the continued airworthiness of
these airplanes in Canada.
Although the effectivity of the service bulletin includes certain
Model DHC-8-100 and -300 series airplanes, Canadian AD No. CF-93-24 is
applicable only to certain Model DHC-8-100 series airplanes. The
service bulletin states that the potentiometer stops on certain Model
DHC-8-300 series airplanes are contacted by the lever prematurely,
resulting in deformation of the stops. However, the FAA has been
advised that, although deformation of the potentiometer stops on these
airplanes can occur, excessive potentiometer lever movement would still
be restricted in the event of failure of a mechanical link. In light of
this information, the FAA finds that Model DHC-8-300 series airplanes
are not subject to the addressed unsafe condition.
This airplane model is manufactured in Canada and is type
certificated for operation in the United States under the provisions of
Sec. 21.29 of the Federal Aviation Regulations and the applicable
bilateral airworthiness agreement. Pursuant to this bilateral
airworthiness agreement, Transport Canada Aviation has kept the FAA
informed of the situation described above. The FAA has examined the
findings of Transport Canada Aviation, 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.
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 modification of the
potentiometer lever stops on the nose wheel steering. The actions would
be required to be accomplished in accordance with the service bulletin
described previously.
The FAA estimates that 48 airplanes of U.S. registry would be
affected by this proposed AD, that it would take approximately 3 work
hours per airplane to accomplish the proposed actions, and that the
average labor rate is $55 per work hour. The cost for required parts
would be minimal. Based on these figures, the total cost impact of the
proposed AD on U.S. operators is estimated to be $7,920, or $165 per
airplane.
The total 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.
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 14
CFR part 39 of the Federal Aviation Regulations as follows:
PART 39--AIRWORTHINESS DIRECTIVES-
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
De Havilland, Inc.: Docket 94-NM-06-AD.
Applicability: Model DHC-8-102, -103, and -106 airplanes, serial
numbers 003 through 334 inclusive; certificated in any category.
Compliance: Required as indicated, unless accomplished
previously.
To prevent the airplane from departing the runway during takeoff
or landing, accomplish the following:
(a) Within 6 months after the effective date of this AD, modify
the potentiometer lever stops on the nose wheel steering in
accordance with de Havilland Service Bulletin S.B. 8-32-99, Revision
``A,'' dated July 26, 1993.
(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, New York Aircraft Certification
Office (ACO), FAA, Engine and Propeller Directorate.
Operators shall submit their requests through an appropriate FAA
Principal Maintenance Inspector, who may add comments and then send
it to the Manager, New York ACO.
Note: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the New York ACO.
(c) Special flight permits may be issued in accordance with
Federal Aviation Regulations (FAR) 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 April 1, 1994.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-8326 Filed 4-6-94; 8:45 am]
BILLING CODE 4910-13-U
