Airworthiness Directives: de Havilland DHC-6 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-CE-52-AD]

Airworthiness Directives: de Havilland DHC-6 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes to adopt a new airworthiness directive

(AD) that would apply to de Havilland DHC-6 series airplanes. The

proposed action would require repetitively inspecting the horizontal

stabilizer center hinge bracket for cracks, and replacing any cracked

center hinge bracket. Several reports of cracks in the horizontal

stabilizer center hinge bracket flange on the affected airplanes

prompted the proposed action. The actions specified by the proposed AD

are intended to prevent separation of the elevator control support from

the airplane as a result of a cracked horizontal stabilizer center

hinge bracket, which could result in reduced controllability of the

airplane.

DATES: Comments must be received on or before April 22, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Central Region, Office of the Assistant Chief

Counsel, Attention: Rules Docket No. 93-CE-52-AD, room 1558, 601 E.

12th Street, Kansas City, Missouri 64106. Comments may be inspected at

this location between 8 a.m. and 4 p.m., Monday through Friday,

holidays excepted.

Service information that applies to the proposed AD may be obtained

from de Havilland, Inc., 123 Garratt Boulevard, Downsview, Ontario,

Canada, M3K 1Y5. This information also may be examined at the Rules

Docket at the address above.

FOR FURTHER INFORMATION CONTACT: Jon Hjelm, Aerospace Engineer, FAA,

New York Aircraft Certification Office, 181 South Franklin Avenue, room

202, Valley Stream, New York 11581; telephone (516) 791-6220; facsimile

(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 should 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 that summarizes 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 No. 93-CE-52-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, Central Region, Office of the Assistant Chief Counsel,

Attention: Rules Docket No. 93-CE-52-AD, room 1558, 601 E. 12th Street,

Kansas City, Missouri 64106.

Discussion

Transport Canada, which is the airworthiness authority for Canada,

recently notified the FAA that an unsafe condition may exist on de

Havilland DHC-6 series airplanes. Transport Canada reports that the

horizontal stabilizer center hinge bracket has cracked on several of

the above referenced airplanes.

De Havilland has issued Service Bulletin (SB) 6/512, dated October

25, 1991, which specifies procedures for (1) inspecting the horizontal

stabilizer center hinge bracket for cracks; and (2) replacing this

center hinge bracket. Transport Canada classified this service bulletin

as mandatory and issued Transport Canada AD CF-92-05, dated February 7,

1992, 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 has kept the FAA informed of

the situation described above. The FAA has examined the findings of

Transport Canada, 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 in other de Havilland DHC-6 series airplanes of the

same type design, the proposed AD would require repetitively inspecting

the horizontal stabilizer center hinge bracket for cracks, and

replacing any cracked center hinge bracket. The proposed action would

be accomplished in accordance with the ACCOMPLISHMENT INSTRUCTIONS

section of de Havilland SB 6/512, dated October 25, 1991.

The FAA estimates that 169 airplanes in the U.S. registry would be

affected by the proposed AD, that it would take approximately 1

workhour per airplane to accomplish the proposed inspection, and that

the average labor rate is approximately $55 an hour. Based on these

figures, the total cost impact of the proposed AD on U.S. operators is

estimated to be $9,295. This figure only includes the cost for the

initial inspection and does not include replacement costs if a center

hinge bracket was found cracked nor does it include repetitive

inspection costs. The FAA has no way to determine how many center hinge

brackets may be cracked or how many repetitive inspections each owner/

operator may incur.

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 action (1) is

not a ``significant regulatory action'' under Executive Order 12866;

(2) is not a ``significant rule'' under 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 has been placed 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 AD to read

as follows:

De Havilland: Docket No. 93-CE-52-AD.

Applicability: Models DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-

300 airplanes (all serial numbers), certificated in any category.

Compliance: Required within the next 250 hours time-in-service

(TIS), unless already accomplished, and thereafter at intervals not

to exceed 1,200 hours TIS.

To prevent separation of the elevator control support from the

airplane as a result of a cracked horizontal stabilizer center hinge

bracket, which could result in reduced controllability of the

airplane, accomplish the following:

(a) Inspect the horizontal stabilizer center hinge bracket for

cracks in accordance with the ACCOMPLISHMENT INSTRUCTIONS section of

de Havilland Service Bulletin 6/512, dated October 25, 1991, except

that where dye penetrant inspections are specified, accomplish

visual inspections with a strong light source and 10X magnifying

glass. If any cracks are found, prior to further flight, replace the

center hinge bracket in accordance with the referenced service

bulletin.

Note 1: The repetitive inspection requirement of this AD still

applies if the center hinge bracket is replaced.

(b) Special flight permits may be issued in accordance with 14

CFR 21.197 and 21.199 to operate the airplane to a location where

the requirements of this AD can be accomplished.

(c) An alternative method of compliance or adjustment of the

initial or repetitive compliance times that provides an equivalent

level of safety may be approved by the Manager, New York Aircraft

Certification Office (ACO), FAA, 181 South Franklin Avenue, room

202, Valley Stream, New York 11581. The request shall be forwarded

through an appropriate FAA Maintenance Inspector, who may add

comments and then send it to the Manager, New York ACO.

Note 2: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the New York ACO.

(d) All persons affected by this directive may obtain copies of

the document referred to herein upon request to de Havilland, Inc.,

123 Garratt Boulevard, Downsview, Ontario M3K 1Y5 Canada; or may

examine this document at the FAA, Central Region, Office of the

Assistant Chief Counsel, room 1558, 601 E. 12th Street, Kansas City,

Missouri 64106.

Issued in Kansas City, Missouri, on February 11, 1994.

Michael K. Dahl,

Acting Manager, Small Airplane Directorate, Aircraft Certification

Office.

[FR Doc. 94-3576 Filed 2-16-94; 8:45 am]

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