Airworthiness Directives; Fokker Model F28 Mark 0100 Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-38-AD]

Airworthiness Directives; Fokker Model F28 Mark 0100 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 Fokker Model F28 Mark 0100

series airplanes. This proposal would require replacement of the

autopilot disconnect switches with modified units. This proposal is

prompted by several incidents in which the flight crew did not depress

both halves of the autopilot disconnect switch during the LAND 2 or

LAND 3 approach and, as a result, one autopilot remained engaged. This

condition resulted in unanticipated movements of the stabilizer trim

and higher than anticipated control forces of the flight controls. The

actions specified by the proposed AD are intended to prevent the flight

crew from inadvertently disconnecting only one autopilot when both

autopilots are engaged, which could result in unanticipated control

surface movements.

DATES: Comments must be received by June 20, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 94-NM-38-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 Fokker Aircraft USA, Inc., 1199 North Fairfax Street,

Alexandria, Virginia 22314. This information may be examined at the

FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton,

Washington.

FOR FURTHER INFORMATION CONTACT: Tim Dulin, Aerospace Engineer,

Standardization Branch, ANM-113, FAA, Transport Airplane Directorate,

1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone (206)

227-2141; fax (206) 227-1320.

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-38-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-38-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

The Rijksluchtvaartdienst (RLD), which is the airworthiness

authority for the Netherlands, recently notified the FAA that an unsafe

condition may exist on certain Fokker Model F28 Mark 0100 series

airplanes. The RLD advises that operators have reported several

incidents in which the flight crew did not depress both halves of the

autopilot disconnect switch during the LAND 2 or LAND 3 approach and,

as a result, one autopilot remained engaged. Although certain aural

warnings sounded and visual indicators illuminated in these situations,

the flight crew still believed that both autopilots had been

disconnected. Consequently, unanticipated movements of the stabilizer

trim and higher than anticipated control forces of the flight controls

occurred. Inadvertent disconnection of only one autopilot when both

autopilots are engaged could result in unanticipated control surface

movements.

Fokker has issued Service Bulletin SBF100-22-020, dated September

25, 1990, that describes procedures for replacement of the autopilot

disconnect switches with modified units. Installation of the modified

units will ensure that if one-half of the autopilot disconnect switch

is depressed, both autopilots will disengage; in addition, the system

will remain separated. The RLD classified this service bulletin as

mandatory and issued Netherlands Airworthiness Directive 90-112(A),

dated October 15, 1990, in order to assure the continued airworthiness

of these airplanes in the Netherlands.

This airplane model is manufactured in the Netherlands 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, the RLD has kept the FAA informed of the

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

RLD, 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 replacement of the

autopilot disconnect switches with modified units. The actions would be

required to be accomplished in accordance with the service bulletin

described previously.

The FAA estimates that 19 airplanes of U.S. registry would be

affected by this proposed AD, that it would take approximately 8 work

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

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

approximately $2,500 per airplane. Based on these figures, the total

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

$55,860, or $2,940 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:

Fokker: Docket 94-NM-38-AD.

Applicability: Model F28 Mark 0100 series airplanes; serial

numbers 11244 through 11286 inclusive, 11289 through 11293

inclusive, 11295 through 11297 inclusive, 11300, 11303, 11306,

11308, 11310, 11312, and 11313; certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent the flight crew from inadvertently disconnecting only

one autopilot when both autopilots are engaged, which could result

in unanticipated control surface movements, accomplish the

following:

(a) Within 6 months after the effective date of this AD, replace

the autopilot disconnect switches with modified units, in accordance

with Fokker Service Bulletin SBF100-22-020, dated September 25,

1990.

(b) As of 6 months after the effective date of this AD, no

person shall install an autopilot disconnect switch, part number

A47007-401 or A47007-403, on any airplane.

(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, Standardization Branch, ANM-113,

FAA, Transport Airplane Directorate. Operators shall submit their

requests through an appropriate FAA Principal Maintenance Inspector,

who may add comments and then send it to the Manager,

Standardization Branch, ANM-113.

Note: Information concerning the existence of approved

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

obtained from the Standardization Branch, ANM-113.

(d) Special flight permits may be issued in accordance with

Federal Aviation Regulations (FAR) Sec. 21.197 and Sec. 21.199 to

operate the airplane to a location where the requirements of this AD

can be accomplished.

Issued in Renton, Washington, on May 5, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certificate

Service.

[FR Doc. 94-11353 Filed 5-10-94; 8:45 am]

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