Airworthiness Directives; Saab Model SF340A and SAAB 340B Series Airplanes

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-NM-234-AD; Amendment 39-9018; AD 94-18-05]

Airworthiness Directives; Saab Model SF340A and SAAB 340B Series

Airplanes

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 SF340A and SAAB 340B series airplanes.

This amendment requires inspections to detect discrepancies of certain

main landing gear (MLG) retract actuator bracket retaining bolts;

replacement of discrepant parts; installation of washers, if necessary;

and eventual replacement of certain MLG retract actuator bracket

retaining bolts and certain nose landing gear (NLG) trunnion pin cross

bolts. This amendment is prompted by reports of extension and

retraction problems on the MLG, due to loose retract actuator brackets

on the MLG shock struts. The actions specified by this AD are intended

to prevent a loose retract actuator bracket from interfering with the

MLG shock strut trunnion support, which could result in the inability

of the MLG to extend or retract.

DATES: Effective October 11, 1994.

The incorporation by reference of certain publications listed in

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

of October 11, 1994.

ADDRESSES: The service information referenced in this AD may be

obtained from Saab Aircraft AB, Product Support, S581.88, Linkoping,

Sweden. 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 certain Saab Model SF340A and SAAB

340B series airplanes was published in the Federal Register on March

24, 1994 (59 FR 13898). That action proposed to require a one-time

visual inspection to detect corrosion, cracking, or damage of certain

MLG retract actuator bracket retaining bolts and to determine if the

nut is bottoming the threads of certain other bolts; replacement of any

discrepant bolt; and the installation of washers, if any nut is found

bottoming the threads. It also proposed to require a one-time visual

and magnaflux inspection during MLG overhaul to detect any scored,

cracked, or out-of-tolerance condition of certain MLG retract actuator

bracket retainer bolts; replacement of any discrepant bolt; and

eventual replacement of certain MLG retract actuator bracket retaining

bolts and certain NLG trunnion pin cross bolts.

Interested persons have been afforded an opportunity to participate

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

the comments received.

One commenter supports the proposal.

Another commenter requests that the proposed rule be revised to

include reference to Revision 1 of the specified Saab service bulletin.

The FAA concurs. Since issuance of the notice, Saab has issued Revision

1 of Service Bulletin 340-32-094, dated March 4, 1994. This revised

service bulletin is essentially identical to the originally released

version, which was referenced in the notice, but contains certain

clarifications, revised illustrations, and provisions for use of an

alternative washer. The Luftfartsverket, which is the airworthiness

authority for Sweden, has approved the technical content of this

revised service bulletin. The FAA has revised the final rule to include

reference to the revised service bulletin as an additional source of

appropriate service information.

This same commenter requests clarification as to whether or not the

proposed rule would require replacement of corroded bolts if any were

found during the magnaflux inspection that would be required by

paragraph (b)(1) of the proposal. The FAA notes that the Saab Service

Bulletin 340-32-094, which is referenced in the notice, mentions

hydrogen embrittlement (corrosion) as one of the reasons for fractures

of the subject retaining bolts; however, that service bulletin does not

directly address corrosion in its instructions for inspection. That

service bulletin does contain attachments comprised of several AP

Precision Hydraulic, Ltd., service bulletins, however, and several of

those service bulletins do contain instructions for visually inspecting

the retainer bolts for corrosion, cracking, or damage, and removing any

bolt that exhibits such discrepancies. Further, the FAA points out

that, under normal maintenance practices, these bolts are inspected

visually to detect cracks, corrosion, or other damage whenever they are

removed, and are replaced if discrepancies exist. Since the bolts must

be removed for the visual and magnaflux inspections required by

paragraph (b)(1) of the rule, they would necessarily be inspected for

corrosion at that time if normal maintenance practices are followed.

The FAA has added ``Note 1'' to paragraph (b)(1) of the final rule to

remind operators of the need to visually inspect the bolts for

corrosion and to replace any corroded bolts.

After careful review of the available data, including the comment

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 217 airplanes of U.S. registry will be

affected by this AD, that it will take approximately 4 work hours per

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

rate is $55 per work hour. Required parts will be provided at no cost

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

on U.S. operators is estimated to be $47,740, or $220 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:

94-18-05 Saab Aircraft AB: Amendment 39-9018. Docket 93-NM-234-AD.

Applicability: Saab Model SF340A series airplanes, serial

numbers 004 through 159, inclusive; and SAAB 340B series airplanes,

serial numbers 160 through 346, inclusive; certificated in any

category.

Compliance: Required as indicated, unless accomplished

previously.

To prevent the inability of the main landing gear (MLG) to

extend or retract, accomplish the following:

(a) Within 600 landings after the effective date of this AD, or

within 120 days after the effective date of this AD, whichever

occurs earlier, accomplish the requirements of paragraphs (a)(1) and

(a)(2) in accordance with Paragraphs 2.A. and 2.B. of the

Accomplishment Instructions of Saab Service Bulletin 340-32-094,

dated October 29, 1993, or Revision 1, dated March 4, 1994.

(1) Perform a visual inspection of each MLG retract actuator

bracket retaining bolt, Item 792A or 792 [part number (P/N) AIR

124792], as applicable, to detect corrosion, cracking, or damage, in

accordance with the service bulletin. If any corrosion, cracking, or

damage is detected during that inspection, prior to further flight,

replace the existing bolt with a new or serviceable bolt in

accordance with the service bulletin.

(2) Perform a visual inspection of each MLG retract actuator

bracket retaining bolt, Item 840 (P/N AIR 123940), to determine if

the nut of the bolt is bottoming the threads in accordance with the

service bulletin. If any nut bottoms the threads, prior to further

flight, install washers in accordance with the service bulletin.

(b) At the next MLG overhaul, or within 12,000 landings after

the effective date of this AD, whichever occurs earlier, accomplish

the requirements of paragraphs (b)(1) and (b)(2) of this AD in

accordance with Paragraphs C. through F. of the Accomplishment

Instructions of Saab Service Bulletin 340-32-094, dated October 29,

1993, or Revision 1, dated March 4, 1994.

(1) Perform a visual and magnaflux inspection of each MLG

retract actuator bracket retainer bolt, Item 792A or 792 (P/N AIR

124792), as applicable, to detect any scored, cracked, or out-of-

tolerance condition, in accordance with the service bulletin. If any

bolt is found to be scored, cracked, or out-of-tolerance, prior to

further flight, replace the bolt with a serviceable magnafluxed bolt

or with a new bolt, in accordance with the service bulletin.

Note 1: In accordance with normal maintenance practices, the

retainer bolts also should be visually inspected for corrosion when

they are removed during the accomplishment of the inspections

required by this paragraph. Any corroded bolt that is detected

should be replaced with a serviceable bolt or a new bolt.

Instructions for performing visual inspections of the retainer bolts

to detect corrosion are contained in Attachments 1, 2, 5, 6, and 7

of Saab Service Bulletin 340-32-094.

(2) Replace each existing MLG retract actuator bracket retaining

bolt, Item 840 (P/N AIR 123940), with a new bolt, P/N AIR 134736, in

accordance with the service bulletin.

(c) At the next MLG overhaul, or within 12,000 landings after

the effective date of this AD, whichever occurs earlier, remove the

existing nose landing gear trunnion pin cross bolt, P/N NAS 1305-

54D, and replace it with a new bolt, P/N NAS 1305-50D, in accordance

with Paragraphs C. through F. of the Accomplishment Instructions of

Saab Service Bulletin 340-32-094, dated October 29, 1993, or

Revision 1, dated March 4, 1994

(d) 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 Manager, Standardization Branch, ANM-113.

(e) 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.

(f) The actions shall be done in accordance with the following

Saab service bulletins, which contain the following list of

effective pages:

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Saab service bulletin and date- Page No.- Revision level -shown on page Date shown on page

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340-32-094, Oct. 29, 1993....... Title page-....... Original-....................... Oct. 29, 1993.

1-5............... (These pages are not dated.)

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-- Attachment 1

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- 1-4-.............. Original-....................... Apr. 1993.

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Attachment 2

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1-4-.............. Original-....................... Apr. 1993.

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Attachment 3

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1-6-.............. Original-....................... Aug. 1993.

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Attachment 4

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1-6-.............. Original-....................... Aug. 1993.

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Attachment 5

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1, 3-............. (These pages are not dated.) June 1993.

2, 4.............. Original........................

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Attachment 6

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1-4-.............. (These pages are not dated.)

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Attachment 7

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- 1-4-.............. (These pages are not dated.)

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Attachment 8

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- 1-4-.............. (These pages are not dated.)

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340-32-094, Revision 1, Mar. 4, Title page-....... 1-.............................. Mar. 4, 1994. -

1994. 1-6............... 1............................... Mar. 4, 1994.

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Attachment 1

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- 2, 4-............. 1-.............................. Jan. 1994.

1, 3.............. Original........................ Apr. 1993.

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Attachment 2

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2, 4-............. 1-.............................. Jan. 1994.

1, 3.............. Original........................ Apr. 1993.

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Attachment 3

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1-4, 6-7-......... 1-.............................. Jan. 1994.

5................. Original........................ Aug. 1993.

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Attachment 4

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1-4, 6-7-......... 1-.............................. Jan. 1994.

5................. Original........................ Aug. 1993.

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Attachment 5

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- 1-5-.............. 2-.............................. Jan. 1994.

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Attachment 6

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- 1-5-.............. 2-.............................. Jan. 1994.

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Attachment 7

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- 1-5-.............. 2-.............................. Jan. 1994.

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Attachment 8

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- 1-5-.............. 2-.............................. Jan. 1994.

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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 Saab Aircraft AB, Product Support,

S581.88, Linkoping, Sweden. 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.

(g) This amendment becomes effective on October 11, 1994.

Issued in Renton, Washington, on August 24, 1994.

N.B. Martenson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 94-21361 Filed 9-8-94; 8:45 am]

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