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

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-76-AD; Amendment 39-8966; AD 94-14-18]

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

Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that

is applicable to certain de Havilland Model DHC-8-100 series airplanes.

This action requires repetitive inspections of the hydraulic selector

valve to determine the rate of leakage of hydraulic fluid, and

replacement of certain valves with serviceable valves, if necessary.

This AD also provides an optional terminating action for the repetitive

inspections. This amendment is prompted by a report of pilot valve

leakage of hydraulic fluid in a landing gear selector valve on a Model

DHC-7 series airplane. The actions specified in this AD are intended to

prevent inadvertent retraction of the landing gear in the event of a

low voltage condition at the selector valve down solenoid.

DATES: Effective July 26, 1994. The incorporation by reference of

certain publications listed in the regulations is approved by the

Director of the Federal Register as of July 26, 1994.

Comments for inclusion in the Rules Docket must be received on or

before September 9, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 94-NM-76-AD, 1601 Lind Avenue, SW., Renton,

Washington 98055-4056.

The service information referenced in this AD 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;

or at the Office of the Federal Register, 800 North Capitol Street NW.,

suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Danko Kramar, Aerospace 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-

6428; fax (516) 791-9024.

SUPPLEMENTARY INFORMATION: 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 advises that it has received a

report of pilot valve leakage of hydraulic fluid in a landing gear

selector valve on a Model DHC-7 series airplane. The cause of this

leakage has been attributed to a faulty seal. Such leakage, if combined

with a low voltage condition at the selector valve down solenoid, could

result in inadvertent retraction of the landing gear.

Since the same selector valve that is used on Model DHC-7 series

airplanes is installed on Model DHC-8-100 series airplanes, the FAA

finds that the latter airplane model also is subject to the addressed

unsafe condition. The FAA may consider issuance of parallel rulemaking

action to address this unsafe condition on Model DHC-7 series

airplanes.

De Havilland, Inc., has issued Alert Service Bulletin S.B. A8-32-

117, dated December 11, 1992, that describes procedures for repetitive

inspections of the hydraulic selector valve to determine the rate of

leakage of hydraulic fluid, and replacement of certain valves with

serviceable valves, if necessary. Transport Canada Aviation classified

this service bulletin as mandatory and issued Canadian Airworthiness

Directive CF-94-05, dated March 16, 1994, in order to assure the

continued airworthiness of these airplanes in Canada.

De Havilland, Inc., also has developed a valve (Modification 8/

0530) that incorporates several improvements to minimize pilot valve

leakage. This valve is equipped with an improved spring that keeps the

valve firmly seated. The improved valve incorporates a reduced rate of

opening and further restricts the orifice leading to the landing gear

actuators. Replacement of certain valves with these improved valves

will minimize the possibility of inadvertent landing gear retraction.

This airplane model is manufactured in Canada 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, 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, this AD is being issued to prevent inadvertent

retraction of the landing gear in the event of a low voltage condition

at the selector valve down solenoid. This AD requires repetitive

inspections of the hydraulic selector valve to determine the rate of

leakage of hydraulic fluid, and replacement of certain valves with

serviceable valves, if necessary. This AD also provides an optional

terminating action for the repetitive inspections. The actions are

required to be accomplished in accordance with the alert service

bulletin described previously.

Since a situation exists that requires the immediate adoption of

this regulation, it is found that notice and opportunity for prior

public comment hereon are impracticable, and that good cause exists for

making this amendment effective in less than 30 days.

Comments Invited

Although this action is in the form of a final rule that involves

requirements affecting flight safety and, thus, was not preceded by

notice and an opportunity for public comment, comments are invited on

this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All

communications received on or before the closing date for comments will

be considered, and this rule may be amended in light of the comments

received. Factual information that supports the commenter's ideas and

suggestions is extremely helpful in evaluating the effectiveness of the

AD action and determining whether additional rulemaking action would be

needed.

Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the rule that might

suggest a need to modify the 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 that

summarizes each FAA-public contact concerned with the substance of this

AD 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-76-AD.'' The postcard will be date stamped and

returned to the commenter.

The regulations adopted herein will 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 final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

The FAA has determined that this regulation is an emergency

regulation that must be issued immediately to correct an unsafe

condition in aircraft, and is not a ``significant regulatory action''

under Executive Order 12866. It has been determined further that this

action involves an emergency regulation under DOT Regulatory Policies

and Procedures (44 FR 11034, February 26, 1979). If it is determined

that this emergency regulation otherwise would be significant under DOT

Regulatory Policies and Procedures, a final regulatory evaluation will

be prepared and placed in the Rules Docket. A copy of it, if filed, may

be obtained from the Rules Docket at the location provided under the

caption ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by

reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends 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. 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:

94-14-18 de Havilland, Inc.: Amendment 39-8966. Docket 94-NM-76-AD.

Applicability: Model DHC-8-100 series airplanes; serial numbers

003 through 038 inclusive; equipped with landing gear selector

valve, part number 57420 or 57420-3; certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent inadvertent retraction of the landing gear due to

pilot valve leakage, accomplish the following:

(a) Within 300 hours time-in-service after the effective date of

this AD, inspect the hydraulic selector valve to determine the rate

of leakage of hydraulic fluid, in accordance with the Accomplishment

Instructions of de Havilland Alert Service Bulletin S.B. A8-32-117,

dated December 11, 1992.

(1) If the rate of leakage is 100 cubic centimeters (cc) per

minute or less: Repeat the inspection required by paragraph (a) of

this AD thereafter at intervals not to exceed 10,000 hours time-in-

service.

(2) If the rate of leakage is more than 100 cc per minute, but

less than 1,000 cc per minute: Within 300 hours time-in-service,

replace the hydraulic selector valve with a serviceable valve in

accordance with the alert service bulletin. Thereafter, repeat the

inspection required by paragraph (a) of this AD at intervals not to

exceed 10,000 hours time-in-service.

(3) If the rate of leakage is 1,000 cc or more per minute, but

less than 1,500 cc per minute: Within 50 hours time-in-service,

replace the hydraulic selector valve with a serviceable valve in

accordance with the alert service bulletin. Thereafter, repeat the

inspection required by paragraph (a) of this AD at intervals not to

exceed 10,000 hours time-in-service.

(4) If the rate of leakage is 1,500 cc or more per minute: Prior

to further flight, replace the hydraulic selector valve with a

serviceable valve in accordance with the alert service bulletin.

Thereafter, repeat the inspection required by paragraph (a) of this

AD at intervals not to exceed 10,000 hours time-in-service.

(b) Replacement of the hydraulic selector valve, part number

57420 or 57420-3, with an improved valve (Modification 8/0530), part

number 57420-5, constitutes terminating action for the requirements

of 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, 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

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.

(e) The inspections and replacement shall be done in accordance

with de Havilland Alert Service Bulletin S.B. A8-32-117, dated

December 11, 1992. This incorporation by reference was approved by

the Director of the Federal Register in accordance with 5 U.S.C.

552(a) and 1 CFR part 51. Copies may be obtained from de Havilland,

Inc., Garratt Boulevard, Downsview, Ontario M3K 1Y5, Canada. Copies

may be inspected 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; or at the

Office of the Federal Register, 800 North Capitol Street, NW., suite

700, Washington, DC.

(f) This amendment becomes effective on July 26, 1994.

Issued in Renton, Washington, on June 30, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-16406 Filed 7-8-94; 8:45 am]

BILLING CODE 4910-13-U