[Federal Register Volume 59, Number 57 (Thursday, March 24, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-6909]


[[Page Unknown]]

[Federal Register: March 24, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-NM-234-AD]

 

Airworthiness Directives; Saab Model SF340A and SAAB 340B 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 certain Saab Model SF340A and SAAB 
340B series airplanes. This proposal would require 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 proposal 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 the proposed 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: Comments must be received by May 17, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 93-NM-234-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 Saab Aircraft AB, Product Support, S581.88, Linko-ping, 
Sweden. 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 93-NM-234-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. 93-NM-234-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The Luftfartsverket, which is the airworthiness authority for 
Sweden, recently notified the FAA that an unsafe condition may exist on 
certain Saab Model SF340A and SAAB 340B series airplanes. The 
Luftfartsverket advises that several operators have reported extension 
and retraction problems on the main landing gear (MLG) due to loose 
retract actuator brackets on the MLG shock struts. These difficulties 
were caused by the shearing at the head of one of the two bracket 
retaining bolts. Laboratory investigations have revealed that the 
fracture of the retaining bolt has been attributed to fatigue or 
hydrogen embrittlement (corrosion). There have also been some cases 
where the retaining bolt for the bonding strap had not been installed 
with a proper amount of washers. This can reduce pre-tension of the 
bolt and allow the bracket to move and apply excessive load on the 
retaining bolts, and can lead to fatigue fracture of the retract 
actuator bracket retaining bolt. A loose retract actuator bracket, if 
not detected and corrected in a timely manner, could interfere with the 
MLG shock strut trunnion support, and subsequently result in the 
inability of the MLG to extend or retract.
    Saab has issued Service Bulletin 340-32-094, dated October 29, 
1993, that describes procedures for 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 corroded, cracked, 
or damaged bolt; and the installation of washers, if any nut is found 
bottoming the threads. The service bulletin also describes procedures 
for 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 nose landing gear (NLG) 
trunnion pin cross bolts. The Luftfartsverket classified this service 
bulletin as mandatory and issued Swedish Airworthiness Directive (SAD) 
No. 1-061, dated November 15, 1993, in order to assure the continued 
airworthiness of these airplanes in Sweden.
    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 Luftfartsverket has kept the FAA informed 
of the situation described above. The FAA has examined the findings of 
the Luftfartsverket, 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 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. The proposed AD would also 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. The actions 
would be required to be accomplished in accordance with the service 
bulletin described previously.
    The FAA estimates that 217 airplanes of U.S. registry would be 
affected by this proposed AD, that it would take approximately 4 work 
hours per airplane to accomplish the proposed 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 proposed 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 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 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.
    (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.
    (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.
    (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.
    (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: 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 
Federal Aviation Regulations (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 March 18, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-6909 Filed 3-23-94; 8:45 am]
BILLING CODE 4910-13-U