Airworthiness Directives; British Aerospace Model BAe 146-100A, - 200A, and -300A Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-126-AD]

Airworthiness Directives; British Aerospace Model BAe 146-100A, -

200A, and -300A 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 British Aerospace Model BAe

146-100A, -200A, and -300A series airplanes. This proposal would

require conducting closed loop tests to determine the setting of the

underfrequency trip level on suspect generator control units (GCU), and

either the correction of discrepancies or replacement of the GCU. This

proposal is prompted by several malfunctions of in-service GCU's due to

the effects of setting the underfrequency trip level too high. The

actions specified by the proposed AD are intended to correct GCU's that

may have the underfrequency level set too high, which could result in

the unwanted shut down of an electrical generator; this condition may

lead to loss of all generated electrical power on the airplane when

other generator faults or failures occur.

DATES: Comments must be received by January 13, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 94-NM-126-AD, 1601 Lind Avenue, SW.,

Renton, Washington 98055-4056. Comments may be inspected at this

location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except

Federal holidays.

The service information referenced in the proposed rule may be

obtained from British Aerospace Holdings, Inc., Avro International

Aerospace Division, P.O. Box 16039, Dulles International Airport,

Washington DC 20041-6039; and GEC-Marconi Aerospace Ltd, Titchfield,

Fareham, Hampshire P014 4QA, England. This information may be examined

at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW.,

Renton, Washington.

FOR FURTHER INFORMATION CONTACT: William Schroeder, Aerospace Engineer,

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

Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056;

telephone (206) 227-2148; 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-126-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-126-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

Discussion

The Civil Aviation Authority (CAA), which is the airworthiness

authority for the United Kingdom, recently notified the FAA that an

unsafe condition may exist on all British Aerospace Model BAe 146-100A,

-200A, and -300A series airplanes. The CAA advises that reports have

been received of several malfunctions of in-service generator control

units (GCU). Investigation revealed that GCU's repaired or adjusted by

workshops other than GEC-Marconi may have the underfrequency trip level

set too high. The cause has been attributed to the fact that the GEC-

Marconi Component Maintenance Manual does not recommend that the

underfrequency trip level be checked during the closed loop test. (GEC-

Marconi is the manufacturer of the subject GCU's.) Setting the

underfrequency level too high could lead to the shut down of an

electrical generator. If an electrical generator shuts down when other

generator faults or failures occur, all generated electrical power on

the airplane may be lost.

Avro International Aerospace (a division of British Aerospace) has

issued Service Bulletin S.B. 24-103, dated March 24, 1994, which

describes procedures for checking the part and serial number on the

data plate of each GCU to identify discrepant units, replacing the

discrepant GCU with a serviceable unit, and conducting post assembly

testing. The CAA classified this service bulletin as mandatory.

GEC-Marconi has issued Service Bulletin HGE 24-23, dated March 11,

1994, which describes procedures for conducting closed loop tests to

determine the setting of the underfrequency trip level, adjusting the

underfrequency trip level, and conducting post assembly testing. This

service bulletin also describes the part and serial number of affected

GCU's.

This airplane model is manufactured in the United Kingdom and is

type certificated for operation in the United States under the

provisions of Sec. 21.29 of the Federal Aviation Regulations (14 CFR

21.29) and the applicable bilateral airworthiness agreement. Pursuant

to this bilateral airworthiness agreement, the CAA has kept the FAA

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

findings of the CAA, 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 checking the part

and serial number on the data plate of each GCU to identify discrepant

units, and conducting closed loop tests on affected GCU's to determine

the setting of the underfrequency trip level. The proposed AD would

also require either adjusting the underfrequency trip level or

replacing the discrepant GCU with a serviceable unit, and conducting

post assembly testing. The actions would be required to be accomplished

in accordance with the service bulletins described previously.

The FAA estimates that 43 airplanes of U.S. registry would be

affected by this proposed AD, that it would take approximately 1 work

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

average labor rate is $60 per work hour. Based on these figures, the

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

be $2,580, or $60 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

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:

British Aerospace Regional Aircraft Limited, AVRO International

Aerospace Division (Formerly British Aerospace, plc; British

Aerospace Commercial Aircraft Limited): Docket 94-NM-126-AD.

Applicability: All Model British Aerospace Model BAe 146-100A, -

200A, and -300A series airplanes, certificated in any category.

Compliance: Required as indicated, unless accomplished

previously. -To correct generator control units (GCU) that may have

the under-frequency trip level set too high, which could lead to the

unwanted shut down of an electrical generator, accomplish the

following:

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

the part and serial number on the data plate of each generator

control unit (GCU). If the part number is one of those affected and

the serial number is listed in Addendum 1 of GEC-Marconi Service

Bulletin HGE 24-23, dated March 11, 1994, prior to further flight,

conduct a closed loop test to determine the setting of the

underfrequency trip level, in accordance with that service bulletin.

(1) If the level exceeds that specified in GEC-Marconi Service

Bulletin HGE 24-23, dated March 11, 1994, prior to further flight,

adjust the level in accordance with that service bulletin; or

replace the GCU with a serviceable unit, in accordance with Avro

Service Bulletin S.B. 24-103, dated March 24, 1994.

(2) Prior to further flight, after adjustment or replacement of

the GCU as required by paragraph (a)(1) of this AD, conduct the post

assembly testing in accordance with Avro Service Bulletin S.B. 24-

103, dated March 24, 1994.

(b) 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.

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

Secs. 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.

Issued in Renton, Washington, on November 9, 1994.

S.R. Miller, Acting Manager,

Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. 94-28245 Filed 11-15-94; 8:45 am]

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