Airworthiness Directives; Saab Model SAAB SF340A and SAAB 340B Airplanes, Equipped With Flight Equipment and Engineering Limited Model 121 Series Seats

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-NM-23-AD]

Airworthiness Directives; Saab Model SAAB SF340A and SAAB 340B

Airplanes, Equipped With Flight Equipment and Engineering Limited Model

121 Series Seats

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 Saab Model SAAB SF340A and

SAAB 340B airplanes. This proposal would require repetitive inspections

to detect cracking of the tray stop spindle and backrest spindle bosses

on the inboard sections of certain seats; and replacement of the

inboard sections, if necessary. This proposal would also require repair

and identification of the modification plate, which would terminate the

requirement to inspect repetitively. This proposal is prompted by

reports of fatigue cracking in the vicinity of the tray stop spindle

and backrest spindle bosses, which could lead to excessive movement and

eventual failure of the backrest on these seats during aft loading. The

actions specified by the proposed AD are intended to prevent failure of

the backrest on these seats, which could inhibit emergency egress.

DATES: Comments must be received by June 27, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Attention: Rules Docket No. 94-NM-23-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 Flight Equipment and Engineering Limited, Technical

Manager, Nissen House, Grovebury Road, Leighton Buzzard, Bedfordshire,

LU7 8TB, United Kingdom. This information may be examined at the FAA,

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

Washington.

FOR FURTHER INFORMATION CONTACT: Mark Quam, Aerospace Engineer,

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

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

227-2145; 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-23-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-23-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 Flight Equipment and Engineering

Limited (FEEL) Model 121 series seats that are installed on Saab Model

SAAB SF340A and SAAB 340B airplanes. The CAA advises that several

operators of Saab Model SAAB SF340A and SAAB SF340B airplanes found

fatigue cracking in the vicinity of the tray stop spindle and backrest

spindle bosses. Cracking in this area may weaken the machined component

that attaches the backrest of the seats to the main spars of the

airplane and may lead to excessive movement and eventual failure of the

backrest on these seats during aft loading. This condition, if not

corrected, could result in failure of the backrest of these seats,

which could inhibit emergency egress.

FEEL has issued Service Bulletin 25-20-1287, Revision 3, dated

March 1993, that describes procedures for a detailed visual inspection

to detect cracking of the tray stop spindle and backrest spindle bosses

on the inboard section of certain Model 121 series seats; replacement

of the inboard section with a section having the same part number, if

necessary, and repetitively inspecting; and identification of the newly

installed section.

FEEL has also issued Service Bulletin 25-20-1294, Revision 1, dated

May 1993, that describes procedures for repair by replacing the inboard

section of certain Model 121 series seats with a newly designed,

stronger inboard section, and replacing the front beam with a

serviceable beam, if necessary; and identification of the newly

installed section. This repair and identification procedure would

eliminate the need to inspect the inboard sections repetitively.

The CAA classified these service bulletins as mandatory and issued

CAA Airworthiness Directives 006-03-93 and 017-03-93 in order to assure

the continued airworthiness of these airplanes in the United Kingdom.

This airplane model is manufactured in Sweden 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 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 a detailed visual

inspection to detect cracking of the tray stop spindle and backrest

spindle bosses on the inboard section of certain Model 121 series

seats; replacement of the inboard sections with sections having the

same part number and repetitively inspecting, if necessary; and

identification of the newly installed section. This proposal would

require repair (including the installation of stronger inboard

sections) and identification of the stronger inboard sections

(accomplishment of the actions specified in FEEL Service Bulletin 25-

20-1294), which would terminate the requirement to inspect

repetitively. The actions would be required to be accomplished in

accordance with the service bulletins described previously.

The FAA estimates that 73 airplanes of U.S. registry would be

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

hours (1 work hour per seat to inspect and 1 work hour per seat to

replace, with 34 seats per airplane) to accomplish the proposed

actions, and that the average labor rate is $55 per work hour. Required

parts would be provided by the manufacturer at no cost to the operator.

Based on these figures, the total cost impact of the proposed AD on

U.S. operators is estimated to be $273,020, or $3,740 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:

SAAB Aircraft AB: Docket 94-NM-23-AD.

Applicability: Model SAAB SF340A airplanes having serial numbers

004 through 159 inclusive, and Model SAAB 340B airplanes having

serial numbers 160 through 330 inclusive; equipped with Flight

Equipment and Engineering Limited (FEEL) Model 121 series seats

listed in FEEL Service Bulletin 25-20-1294, Revision 1, dated May

1993, or FEEL Service Bulletin 25-20-1287, Revision 3, dated March

1993; certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent failure of the backrest on these seats, which could

inhibit emergency egress, accomplish the following:

(a) Within 28 days after the effective date of this AD, perform

a detailed visual inspection to detect cracking of the tray stop

spindle and backrest spindle bosses of the inboard section of the

seat, in accordance with FEEL Service Bulletin 25-20-1287, Revision

3, dated March 1993.

(1) If no cracking is found, or if cracking is found that does

not penetrate the shear web, repeat the inspection of that seat

thereafter at intervals not to exceed 150 hours time-in-service

until the requirements or paragraph (b) of this AD are accomplished.

(2) If any cracking is found that penetrates the shear web,

prior to further flight, replace the inboard section (up to issue

12), and identify the modification plate with ``25-20-1287A,'' in

accordance with the service bulletin. Thereafter, repeat the

inspection at intervals not to exceed 150 hours time-in-service

until the requirements of paragraph (b) of the AD are accomplished.

(b) Within 6 months after the effective date of this AD, repair

and identify the modification plate with ``25-20-1294,'' in

accordance with FEEL Service Bulletin 25-20-1294, Revision 1, dated

May 1993. Accomplishment of the actions required by this paragraph

constitutes terminating action for the requirements of this AD.

(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

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 April 26, 1994.

James V. Devany,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-10508 Filed 5-2-94; 8:45 am]

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