Airworthiness Directives; British Aerospace Model ATP Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-217-AD]

Airworthiness Directives; British Aerospace Model ATP 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 British Aerospace Model

ATP airplanes. This proposal would require inspections of the DC

connections and cooling fans in certain transformer rectifier units

(TRU) to detect damage or overheating and to ensure correct operation,

and repair or replacement, if necessary. This proposal is prompted by a

report of the loss of all DC electrical power, except for the battery

emergency bus, due to failure of the TRU's, which occurred during

flight. The actions specified by the proposed AD are intended to

prevent loss of essential electrical power required to continue safe

flight of the airplane.

DATES: Comments must be received by April 18, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 93-NM-217-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 Jetstream Aircraft, Inc., P.O. Box 16029, Dulles

International Airport, Washington, DC 20041-6029. 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,

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 No. 93-NM-217-AD.'' The postcard will be 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-217-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 certain British Aerospace Model ATP

airplanes. The CAA advises that it has received a report of the loss of

all DC electrical power, except for the battery emergency bus, which

occurred during flight on a Model ATP airplane. The DC electrical power

was lost due to a failure in each of the two transformer rectifier

units (TRU's.) A loose DC connection in the first TRU caused its

failure. The second TRU failed due to overheat damage to a cooling fan

blade in the unit. The airplane landed safely while operating on

battery power. Failure of both TRU's during flight could result in loss

of essential electrical power required to continue safe flight of the

airplane.

Jetstream has issued Service Bulletin ATP-24-58, dated October 29,

1993, which references two Ferranti service bulletins as additional

sources of service information. (Ferranti is the manufacture of the

TRU's). The Ferranti service bulletins are described below. The CAA

classified the Jetstream service bulletin as mandatory.

Ferranti Service Bulletin 24-20-171, dated September 1993,

describes procedures for repetitive visual inspections of the DC

connections to detect any damage or overheating. This service bulletin

also describes procedures for repetitive torque loading inspections of

each DC connection to ensure that torque loads are within specified

limits, and repetitive verification that each terminal stud is secure

in its mounting by visually observing that the stud does not rotate.

Ferranti Service Bulletin 24-20-172, dated September 1993,

describes procedures for repetitive visual inspections of the cooling

fan blades to detect any damage due to overheating, and a test of the

operation of the cooling fan by energizing the relay and confirming

that cooling air exists from the grill on the top of the unit.

This airplane model is manufactured in the United Kingdom and is

type certificated for operation in the United States under the

provisions of Section 21.29 of the Federal Aviation Regulations 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:

1. Repetitive visual inspections of the DC connections to detect

any damage or overheating, and repair, if necessary;

2. Repetitive torque loading inspections of each DC connection to

ensure that torque loads are within specified limits, and verification

that each terminal stud is secure in its mounting;

3. Repetitive visual inspections of the cooling fan blades to

detect any damage due to overheating, and replacement of the fan blade,

if necessary; and

4. Repetitive functional tests of the operation of the cooling fan

by energizing the relay and confirming that cooling air exits from the

grill on the top of the unit, and repair or replacement of any

malfunctioning or damaged cooling fan or cooling fan relay.

The inspection would be required to be accomplished in accordance

with the Ferranti service bulletins described previously. Replacement

and repair actions would be required to be accomplished in accordance

with the airplane maintenance manual or a method approved by the FAA.

The FAA estimates that 10 airplanes of U.S. registry would be

affected by this proposed AD, that it would take approximately 2 work

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

average labor rate is $55 per work hour. Based on these figures, the

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

be $1,100, or $110 per airplane. This total cost figure assumes that no

operator has yet accomplished the proposed requirements of this AD

action.

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:

British Aerospace (Commercial Aircraft), Limited: Docket 93-NM-217-

AD.

Applicability: Model ATP airplanes equipped with Ferranti

Transformer Rectifier Unit TR202A (Pt. No. 84/59100) or TR202B (Pt.

No. 84/60040), certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent loss of essential electrical power required to

continue safe flight of the airplane, accomplish the following:

(a) Within 225 hours time-in-service after the effective date of

this AD, and thereafter at intervals not to exceed 625 hours time-

in-service, accomplish paragraphs (a)(1), (a)(2), (a)(3), and (a)(4)

of this AD.

(1) Perform a visual inspection of the DC connections to detect

any damage or overheating, in accordance with Ferranti Service

Bulletin 24-20-171, dated September 1993. If any damage or

overheating is found, prior to further flight, repair in accordance

with a method approved by Manager, Standardization Branch, ANM-113,

FAA, Transport Airplane Directorate.

(2) Perform a torque loading inspection of each DC connection to

ensure that torque loads are within the limits specified in Ferranti

Service Bulletin 24-20-171, dated September 1993; and, during this

inspection, ensure that each terminal stud is secure in its mounting

by visually observing that the stud does not rotate; in accordance

with Ferranti Service Bulletin 24-20-171, dated September 1993.

(3) Perform a visual inspection of the cooling fan blades to

detect any damage due to overheating, in accordance with Ferranti

Service Bulletin 24-20-172, dated September 1993. If any damage is

found, prior to further flight, replace the fan blade with a

serviceable part in accordance with the airplane maintenance manual.

(4) Perform a functional test of the operation of the cooling

fan by energizing the relay and confirming that cooling air exits

from the grill on top of the unit, in accordance with Ferranti

Service Bulletin 24-20-172, dated September 1993. Prior to further

flight, repair or replace any malfunctioning or damaged cooling fan

or cooling fan relay, in accordance with the airplane maintenance

manual.

(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 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 February 14, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-3755 Filed 2-17-94; 8:45 am]

BILLING CODE 4910-13-M