Airworthiness Directives; British Aerospace Model Viscount 744, 745D, and 810 Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-NM-108-AD]

Airworthiness Directives; British Aerospace Model Viscount 744,

745D, and 810 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

Viscount 744, 745D, and 810 series airplanes. This proposal would

require inspections to detect cracks in the chassis side bracing

structure and in the chassis top strut support intercostals inside the

wings, and replacement of discrepant parts with new parts. This

proposal would also require inspection of the intercostals to determine

the specification of the material, if necessary, and replacement of

discrepant parts with new parts. This proposal is prompted by a report

of cracking in the chassis top strut support intercostal in the side

bracing structure inside the wing due to the effects of metal fatigue.

The actions specified by the proposed AD are intended to prevent such

fatigue-related cracking, which could lead to the failure of the

chassis side bracing structure inside the wings and consequent reduced

structural integrity of the chassis support structure.

DATES: Comments must be received by November 4, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 94-NM-108-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 Regional Aircraft Ltd., Engineering

Support Manager, Military Business Unit, Chadderton Works, Greengate,

Middleton, Manchester M24 1SA, 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-108-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-108-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 Viscount 744,

745D, and 810 series airplanes. The CAA advises that it has received a

report of cracking in the chassis top strut support intercostals of the

side bracing structure inside the wings between stations 81 and 96.

Investigation revealed that such cracking was caused by metal fatigue.

The effects of such fatigue-related cracking could lead to failure of

the chassis top strut support intercostals of the side bracing

structure inside the wings. This condition, if not detected and

corrected in a timely manner, could result in reduced structural

integrity of the chassis support structure.

British Aerospace has issued Viscount Preliminary Technical Leaflet

(PTL) 332, Issue 1, Disc 11 Doc. 4, dated December 2, 1991 (for Model

Viscount 744 and 745D series airplanes), and Viscount PTL 203, Issue 1,

Disc 11 Doc. 2, dated December 2, 1991 (for Model Viscount 810 series

airplanes), which describe procedures for repetitive detailed visual

inspections to detect cracks in the chassis side bracing structure

inside the wings and in the chassis top strut support intercostals

inside the wings, and replacement of discrepant parts with new parts.

These PTL's also describe procedures for an eddy current inspection to

determine the specification of the material of the intercostals, if

necessary; and discarding and replacing discrepant parts with new

parts. The CAA classified these PTL's as mandatory.

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 (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 repetitive detailed

visual inspections to detect cracks in the chassis side bracing

structure and in the chassis top strut support intercostals of the

inner wings, and replacement of discrepant parts with new parts. This

proposed AD would also require an eddy current inspection to determine

the specification of the material of the intercostals, if necessary;

and replacement of discrepant parts with new parts. The actions would

be required to be accomplished in accordance with the PTL's described

previously.

The FAA estimates that 25 Model Viscount 744 and 745D series

airplanes of U.S. registry would be affected by this proposed AD, that

it would take approximately 15 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 $20,625, or $825 per airplane, per

inspection cycle.

The FAA estimates that 4 Model Viscount 810 series airplanes of

U.S. registry would be affected by this proposed AD, that it would take

approximately 15 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 $3,300, or $825 per airplane, per

inspection cycle.

Based on the above figures, the total cost impact of the actions

proposed by this AD on U.S. operators is estimated to be $23,925, or

$825 per airplane, per inspection cycle.

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 (Formerly British

Aerospace Commercial Aircraft Limited, Vickers-Armstrongs Aircraft

Limited): Docket 94-NM-108-AD.

Applicability: All Model Viscount 744, 745D, and 810 series

airplanes, certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent reduced structural integrity of the chassis,

accomplish the following:

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

a detailed visual inspection to detect cracks in the chassis side

bracing structure and in the chassis top strut support intercostals

inside the wings between stations 81 and 96, in accordance with

British Aerospace Viscount Preliminary Technical Leaflet (PTL) 332,

Issue 1, Disc 11 Doc.4, dated December 2, 1991 (for Model Viscount

744 and 745D series airplanes); or British Aerospace Viscount PTL

203, Issue 1, Disc 11 Doc.2, dated December 2, 1991 (for Model

Viscount 810 series airplanes); as applicable.

(1) If no cracking is detected in the chassis side bracing

structure, repeat the inspection thereafter at intervals not to

exceed 1,500 flight hours or 14 months, whichever occurs first.

(2) If any cracking is detected in the chassis side bracing

structure, prior to further flight, replace the cracked side of the

bracing structure with a new structure, in accordance with the

applicable PTL.

(3) If no cracking is detected in the chassis top strut support

intercostal, prior to further flight, perform an eddy current

inspection to determine the specification of the material (either

L72 or L73) of the intercostals, in accordance with the applicable

PTL.

(i) If the material is manufactured from L72, prior to further

flight, replace the chassis top strut support intercostal with and a

new chassis top strut support intercostal, in accordance with the

applicable PTL.

(ii) If the material is manufactured from L73, no further action

is required by paragraph (a)(3) of this AD.

(4) If cracking is detected in the chassis top strut support

intercostal, prior to further flight, replace it with a new chassis

top strut support intercostal, in accordance with the applicable

PTL.

(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

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.

Issued in Renton, Washington, on September 2, 1994.

S.R. Miller,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-22230 Filed 9-8-94; 8:45 am]

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