Airworthiness Directives; De Havilland Model DHC-8 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-20-AD]

Airworthiness Directives; De Havilland Model DHC-8 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 all de Havilland Model DHC-8

series airplanes. This proposal would require removal of the aluminum

or brass hardware in the firewall terminal block and battery shunt

cable assemblies and replacement with steel hardware. This proposal is

prompted by the results of an investigation, which revealed that

corroded aluminum washers in the DC firewall terminal block and battery

shunt cable assemblies may loosen the electrical connections. The

actions specified by the proposed AD are intended to prevent

interruption of DC electrical power due to connections that may have

loosened from corrosion.

DATES: Comments must be received by June 3, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-103,

Attention: Rules Docket No. 94-NM-20-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, room 202, Valley Stream, New York.

FOR FURTHER INFORMATION CONTACT: Peter Cuneo, Electrical 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-20-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-20-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

all de Havilland Model DHC-8 series airplanes. Transport Canada

Aviation advises that the results of an investigation revealed that

aluminum washers used in the DC firewall terminal block and battery

shunt cable assemblies of all Model DHC-8 series airplanes could cause

corrosion at the electrical connections. Such corrosion could either

loosen a connection and/or generate a high electrical resistance at the

connection points. This condition, if not corrected, could result in

interruption of DC electrical power due to connections that may have

loosened from corrosion.

Bombardier, Inc., has issued de Havilland Service Bulletin S.B. 8-

24-47, Revision `A', dated November 29, 1993, that describes procedures

for removal of the aluminum or brass hardware in the firewall terminal

block and battery shunt cable assemblies and replacement with steel

hardware (Modification 8/1984). Transport Canada Aviation classified

this service bulletin as mandatory and issued Canadian Airworthiness

Directive CF-93-31, dated December 17, 1993, in order to assure the

continued airworthiness of these airplanes in Canada.

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 removal of the

aluminum or brass hardware in the firewall terminal block and battery

shunt cable assemblies and replacement with steel hardware

(Modification 8/1984). The actions would be required to be accomplished

in accordance with the service bulletin described previously.

The FAA estimates that 130 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. Required parts would be

nominal in cost. Based on these figures, the total cost impact of the

proposed AD on U.S. operators is estimated to be $21,450, 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-20-AD.

Applicability: All Model DHC-8 series airplanes, certificated in

any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent interruption of DC electrical power due to

connections that may have loosened from corrosion, accomplish the

following:

(a) Within 60 days after the effective date of this AD, remove

the aluminum or brass hardware in the firewall terminal block and

battery shunt cable assemblies and replace with steel hardware

(Modification 8/1984), in accordance with de Havilland Service

Bulletin S.B. 8-24-47, Revision `A,' dated November 29, 1993.

(b) As of the effective date of this AD, no person shall install

on any airplane a terminal block, part number 72470052-101 or

82450068-001, unless it has been previously reworked and bears the

identification 8/1984.

(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, 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.

(d) 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 18, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-9728 Filed 4-21-94; 8:45 am]

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