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; Amendment 39-9083; AD 94-24-10]

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: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to certain Saab Model SAAB SF340A and SAAB 340B airplanes,

that requires 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 amendment also requires repair and identification of the

modification plate, which would terminate the requirement to inspect

repetitively. This amendment 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

this AD are intended to prevent failure of the backrest on these seats,

which could inhibit emergency egress.

DATES: Effective January 6, 1995.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of January 6, 1995.

ADDRESSES: The service information referenced in this AD 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

Federal Aviation Administration (FAA), Transport Airplane Directorate,

Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the

Office of the Federal Register, 800 North Capitol Street, NW., suite

700, Washington, DC.

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: A proposal to amend part 39 of the Federal

Aviation Regulations (14 CFR part 39) to include an airworthiness

directive (AD) that is applicable to Saab Model SAAB SF340A and SAAB

340B airplanes, equipped with Flight Equipment and Engineering Limited

Model 121 series seats, was published in the Federal Register on May 3,

1994 (59 FR 22771). That action proposed to 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. It also proposed to

require repair and identification of the modification plate, which

would terminate the requirement to inspect repetitively.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the single comment received.

The commenter has no objections to the proposal, but questions the

accuracy of the description of the point of failure, as described in

the preamble to the notice. The preamble stated, ``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'' (emphasis added). The commenter implies that it is not

accurate to state that the failure point is where the seat backrests

attach to the main spar of the airplane. The FAA has reconsidered its

previous description and concurs that clarification is warranted. The

FAA finds that the following wording comprises a more accurate

description:

Cracking in this area may eventually weaken the seat section

such that the spindles attaching the table and seat back to the seat

section may break free during crash loads or normal loads. This

condition, if not corrected, could result in failure of the backrest

of these seats, which could inhibit emergency egress.

This clarification of the description of the failure scenario in no

way alters the basis for issuance of this AD or the unsafe condition

addressed by it.

As a result of recent communications with the Air Transport

Association (ATA) of America, the FAA has learned that, in general,

some operators may misunderstand the legal effect of AD's on airplanes

that are identified in the applicability provision of the AD, but that

have been altered or repaired in the area addressed by the AD. Under

these circumstances, at least one operator appears to have incorrectly

assumed that its airplane was not subject to an AD. On the contrary,

all airplanes identified in the applicability provision of an AD are

legally subject to the AD. If an airplane has been altered or repaired

in the affected area in such a way as to affect compliance with the AD,

the owner or operator is required to obtain FAA approval for an

alternative method of compliance with the AD, in accordance with the

paragraph of each AD that provides for such approvals. A note has been

added to this final rule to clarify this requirement.

The FAA has recently reviewed the figures it has used over the past

several years in calculating the economic impact of AD activity. In

order to account for various inflationary costs in the airline

industry, the FAA has determined that it is necessary to increase the

labor rate used in these calculations from $55 per workhour to $60 per

workhour. The economic impact information below has been revised to

reflect this increase in the specified hourly labor rate.

After careful review of the available data, including the comments

noted above, the FAA has determined that air safety and the public

interest require the adoption of the rule with the changes previously

described. The FAA has determined that these changes will neither

increase the economic burden on any operator nor increase the scope of

the AD.

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

affected by this AD, that it will take approximately 2 work hours per

seat to accomplish the required actions, and that the average labor

rate is $60 per work hour. There are usually 34 seats per airplane.

Required parts will be provided by the manufacturer at no cost to the

operator. Based on these figures, the total cost impact of the AD on

U.S. operators is estimated to be $297,840, or $4,080 per airplane.

The total cost impact figure discussed above is based on

assumptions that no operator has yet accomplished any of the

requirements of this AD action, and that no operator would accomplish

those actions in the future if this AD were not adopted.

The regulations adopted herein will 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 final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is

not a ``significant regulatory action'' under Executive Order 12866;

(2) is not a ``significant rule'' under DOT Regulatory Policies and

Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action

and it is contained in the Rules Docket. A copy of it may be obtained

from the Rules Docket at the location provided under the caption

ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by

reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends 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.

39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

94-24-10 SAAB Aircraft AB: Amendment 39-9083. 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, and FEEL Service Bulletin 25-20-1287, Revision 3, dated March

1993; certificated in any category.

Note 1: This AD applies to each airplane identified in the

preceding applicability provision, regardless of whether it has been

modified, altered, or repaired in the area subject to the

requirements of this AD. For airplanes that have been modified,

altered, or repaired so that the performance of the requirements of

this AD is affected, the owner/operator must use the authority

provided in paragraph (c) to request approval from the FAA. This

approval may address either no action, if the current configuration

eliminates the unsafe condition; or different actions necessary to

address the unsafe condition described in this AD. Such a request

should include an assessment of the effect of the changed

configuration on the unsafe condition addressed by this AD. In no

case does the presence of any modification, alteration, or repair

remove any airplane from the applicability of this AD.

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 2: 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.

(e) The inspection shall be done in accordance with FEEL Service

Bulletin 25-20-1287, Revision 3, dated March 1993. The repair and

identification shall be done in accordance with FEEL Service

Bulletin 25-20-1294, Revision 1, dated May 1993, which contains the

following list of effective pages:

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Revision

Page No. level shown Date shown on

on page page

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1-3, 19................................. 1........... May 1993.

4-18.................................... Basic....... Mar. 1993.

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This incorporation by reference was approved by the Director of the

Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part

51. Copies may be obtained from Flight Equipment and Engineering

Limited, Technical Manager, Nissen House, Grovebury Road, Leighton

Buzzard, Bedfordshire LU7 8TB, United Kingdom. Copies may be

inspected at the FAA, Transport Airplane Directorate, 1601 Lind

Avenue, SW., Renton, Washington; or at the Office of the Federal

Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(f) This amendment becomes effective on January 6, 1995.

Issued in Renton, Washington, on November 23, 1994.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-29437 Filed 12-6-94; 8:45 am]

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