Airworthiness Directives; de Havilland Model DHC-8-100 and DHC-8- 300 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-206-AD]

Airworthiness Directives; de Havilland Model DHC-8-100 and DHC-8-

300 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 and DHC-8-300 series airplanes. This proposal would require a

revision to the Airplane Flight Manual (AFM) to advise flight crew

members that certain cockpit indications may reveal faulty anti-

collision strobe light units, and to provide procedures for subsequent

flight crew action. This proposal would also require a modification

that eliminates the need for the AFM revision. This proposal is

prompted by reports that the function of the proximity switch

electronics unit (PSEU) may be adversely effected during operation of

the white anti-collision lights. The actions specified by the proposed

AD are intended to ensure correct operation of the PSEU and its

associated systems.

DATES: Comments must be received by May 31, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 93-NM-206-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 de Havilland, Inc., 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: Michele Maurer, Aerospace Engineer,

Systems and Equipment Branch, ANE-173, New York Aircraft Certification

Office, FAA, Engine and Propeller Directorate, 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 93-NM-206-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. 93-NM-206-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 and DHC-8-300 series airplanes.

Transport Canada Aviation advises that three field reports indicate

that the electrical power supplies of the white anti-collision lights

may develop a fault which produces greater than normal electrical

emissions. The cause of this fault has been attributed to a capacitor

failure in some ``Grimes'' strobe light systems. This electromagnetic

interference can adversely affect the operation of the proximity switch

electronics unit (PSEU) and its associated systems. The following

occurrences have resulted:

1. Flashing of the landing gear green locked down advisory

lights during cruise;

2. Fluctuation of the cabin pressurization rate needle during

cruise;

3. Retraction and extension of roll and ground spoilers during

ground operation;

4. Inoperative nose gear steering subsequent to landing; and

5. Unavailable normal wheel brakes below 35-40 knots.

Incorrect operation of the PSEU and its associated systems may

interfere with or distract the flight crew in carrying out its regular

duties during flight or on the ground, and thus serve to compromise the

safe operation of the airplane.

De Havilland, Inc., has issued Alert Service Bulletin S.B. A8-33-

33, dated May 31, 1993, that describes flight crew and maintenance

procedures to detect faulty power supply units. The alert service

bulletin also describes procedures for replacement of any faulty

``Grimes'' unit with a new or serviceable ``Grimes'' unit, or

installation of a new ``Whelan'' system (Modification 8/1273).

De Havilland, Inc., has also issued Service Bulletin S/B 8-33-19,

`Revision A', dated May 31, 1993, that describes procedures for

installation of Modification 8/1273, which entails replacing the

existing anti-collision strobe light system (consisting of anti-

collision strobe lights, brackets, and power supplies) at all three

locations with the new, improved ``Whelen'' anti-collision strobe light

system. (The ``Whelen'' system includes new dual strobes, new brackets,

and new power supplies.) This new system is considered more durable

than the currently installed anti-collision strobe light system. The

``Whelan'' system also has a back-up strobe light at each position.

Transport Canada Aviation classified these service bulletins as

mandatory and issued Canadian Airworthiness Directive CF-93-20, dated

August 3, 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 revising the

Limitations section of the FAA-approved Airplane Flight Manual (AFM) to

advise flight crew members that certain cockpit indications during in-

flight or ground operations may reveal faulty anti-collision strobe

light units, and to provide procedures for subsequent flight crew

action. This proposal would also require replacement of faulty

``Grimes'' units with new or serviceable ``Grimes'' units or

installation of the new ``Whelan'' system (Modification 8/1273). The

proposed AD would also require eventual replacement of the existing

anti-collision strobe light system with the ``Whelen'' anti-collision

strobe light system (Modification 8/1273) at all three locations. When

accomplished, incorporation of this modification would constitute

terminating action for the requirements of this proposal. Following

incorporation of Modification 8/1273, operators would be permitted to

remove the proposed changes to the AFM. The actions would be required

to be accomplished in accordance with the service bulletins described

previously.

Additionally, applicability of the proposed rule would exclude

those airplanes on which Modification 8/1273 has been accomplished

previously, since airplanes so modified are not subject to the unsafe

condition addressed by this proposed AD. The manufacturer has installed

Modification 8/1273 on airplanes having serial numbers 215 and

subsequent.

The FAA estimates that 74 airplanes of U.S. registry would be

affected by this proposed AD, that it would take approximately 16 work

hours per airplane to accomplish the proposed actions, and that the

average labor rate is $55 per work hour. Required parts for

installation of Modification 8/1273 at all three locations would cost

approximately $1,397 per airplane. Based on these figures, the total

cost impact of the proposed AD on U.S. operators is estimated to be

$168,498, or $2,277 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 93-NM-206-AD.

Applicability: Model DHC-8-102, -103, -302, and -311 series

airplanes, serial numbers 003 through 214 inclusive; on which

Modification 8/1273 (as described in de Havilland Service Bulletin

S/B No. 8-33-19, Revision `A', dated May 31, 1993) has not been

accomplished; certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To ensure correct operation of the proximity switch electronics

unit (PSEU) and its associated systems, accomplish the following:

(a) Within 30 days after the effective date of this AD, revise

the Limitations Section of the FAA-approved Airplane Flight Manual

(AFM) to include the following statement. This may be accomplished

by inserting a copy of this AD into the AFM.

``The electrical power supplies for the white anti-collision

lights may fail and cause the following abnormalities:

--Flashing of the landing gear green locked down advisory lights

during cruise;

--Fluctuation of cabin pressurization rate needle during cruise; and

--Retraction and extension of roll and ground spoilers during ground

operation.

The failure may also result in loss of nose landing gear

steering subsequent to landing, and loss of wheel brakes below 35-40

knots.

If any of these abnormal indications are observed, select A/COL

light switch--RED. Leave the switch in this position for the

remainder of the flight.''

(b) If the flight crew reports the occurrence of any of the

cockpit indications stated in paragraph (a) of this AD: Prior to the

next flight, perform the maintenance procedures to confirm and

isolate the faulty power supply unit, in accordance with paragraph

III., part B, Accomplishment Instructions of de Havilland Alert

Service Bulletin S.B. A8-33-33, dated May 31, 1993.

(1) If any power supply unit is determined to be faulty, prior

to further flight, replace the unit with a new or serviceable

``Grimes'' unit or a new ``Whelen'' system in accordance with the

alert service bulletin.

(2) If the specific unit causing the faults cannot be

determined, prior to further flight, replace all three units with

new or serviceable ``Grimes'' units or a new ``Whelen'' system in

accordance with the alert service bulletin. Installation of a new

``Whelen'' system at all three locations constitutes terminating

action for the requirements of this AD, and after installation, the

AFM revision required by paragraph (a) of this AD may be removed.

(c) Within 6 months after the effective date of this AD, install

Modification 8/1273 (which entails replacement of the existing anti-

collision strobe lights, brackets, and power supplies with the

```Whelen' Anti-Collision Strobe Light System'') at all three

locations, in accordance with de Havilland Service Bulletin S/B No.

8-33-19, `Revision A', dated May 31, 1993. Following installation,

the AFM revision required by paragraph (a) of this AD may be

removed.

(d) 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), ANE-170, 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.

(e) Special flight permits may be issued in accordance with 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 March 30, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-8054 Filed 4-4-94; 8:45 am]

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