AD Amdt-39-11031

[Federal Register Volume 64, Number 27 (Wednesday, February 10, 1999)]
[Rules and Regulations]
[Pages 6522-6526]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 99-3033]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-373-AD; Amendment 39-11031; AD 99-04-07]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to certain Saab Model SAAB SF340A and SAAB 340B series 
airplanes. This action requires a review of the airplane maintenance 
records to identify the bottom engine vibration isolator, an inspection 
of the aft engine vibration isolator to determine whether the 
deflection is within limits, and various follow-on actions. This 
amendment is prompted by issuance of mandatory continuing airworthiness 
information by a foreign civil airworthiness authority. The actions 
specified in this AD are intended to prevent excessive engine 
vibration, which could lead to damage of the nacelle structure and 
result in reduced structural integrity and fire shielding capability of 
the nacelle structure, or which could lead to chafing of the fire 
sensor loop and a consequent nuisance fire warning and result in a 
precautionary engine shutdown.

DATES: Effective February 25, 1999.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director

[[Page 6523]]

of the Federal Register as of February 25, 1999.
    Comments for inclusion in the Rules Docket must be received on or 
before March 12, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-373-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.
    The service information referenced in this AD may be obtained from 
Saab Aircraft AB, SAAB Aircraft Product Support, S-581.88, Linkoping, 
Sweden. This information may be examined 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.

FOR FURTHER INFORMATION CONTACT: Norman B. Martenson, Manager, 
International Branch, ANM-116, FAA, Transport Airplane Directorate, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
227-2110; fax (425) 227-1149.

SUPPLEMENTARY INFORMATION: The Luftfartsverket (LFV), which is the 
airworthiness authority for Sweden, notified the FAA that an unsafe 
condition may exist on certain Saab Model SAAB SF340A and SAAB 340B 
series airplanes. The LFV advises that degraded bottom engine mounts 
have been found on several airplanes. Investigation has revealed that 
the isolator material used in the manufacture of certain bottom engine 
mounts degrades after a short time in service. Such degradation of the 
isolator material changes the damping characteristics of the engine 
support system and results in excessive engine vibration. Such 
excessive engine vibration could lead to damage of the nacelle 
structure, and consequent reduced structural integrity and fire 
shielding capability of the nacelle.
    The LFV also advises that it has received a report of chafing of 
the fire sensor loop on several airplanes. Such chafing also has been 
attributed to excessive engine vibration and could result in a nuisance 
fire warning and a precautionary engine shutdown. Precautionary engine 
shutdown could compromise the safe takeoff of the airplane.
    In addition, the LFV advises that it has received a report 
indicating that the air pressure tube of the engine nacelle was found 
damaged on several airplanes. That damage also has been attributed to 
excessive engine vibration. Damage to the air pressure tube could cause 
loss of cooling to the power turbine discs of the engine, which could 
result in failure of the blades of the power turbine disc, and 
consequent uncontained failure of the engine.

Explanation of Relevant Service Information

    Saab has issued Service Bulletin SAAB 340-71-057, Revision 02, 
dated January 26, 1999, including Attachment 1, dated January 20, 1999. 
The service bulletin describes procedures for a review of the airplane 
maintenance records to identify the bottom engine vibration isolator, a 
visual inspection of the aft engine vibration isolator to determine 
whether the deflection is within limits, and various follow-on actions. 
The follow-on actions, as applicable, include one repetition of the 
visual inspection of the aft engine vibration isolator to determine 
whether the deflection is within limits; a one-time visual inspection 
to detect chafing of the area around the engine; replacement of the 
existing bottom engine vibration isolator with a new part; repair or 
replacement of discrepant parts; visual inspections to detect damage of 
the side and aft engine vibration isolators, and replacement, if 
necessary; and detailed visual inspections to detect cracked or broken 
parts of the engine mount support fitting, adjacent structure, and 
attaching hardware of the bottom, side, and aft engine mount support 
fittings.
    The Saab service bulletin references Barry Controls Service Letter 
939-71-02, dated January 20, 1999, as the appropriate source of 
criteria for the inspection of the bottom vibration isolator. The Saab 
service bulletin includes that service letter as Attachment 1.
    The Saab service bulletin references Barry Controls Component 
Maintenance Manual Section 71-20-20, dated October 15, 1993, as an 
additional source of service information to accomplish the visual 
inspection of the side and aft engine vibration isolators.
    Accomplishment of the actions specified in the Saab service 
bulletin is intended to adequately address the identified unsafe 
condition. The LFV classified Saab Service Bulletin SAAB 340-71-057, 
Revision 1, dated December 18, 1998 (including Attachment 1, dated 
December 11, 1998), as mandatory and issued Swedish airworthiness 
directive SAD 1-135R1, dated December 18, 1998, in order to assure the 
continued airworthiness of these airplanes in Sweden.

FAA's Conclusions

    These airplane models are manufactured in Sweden and are 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 LFV has kept the FAA informed of 
the situation described above. The FAA has examined the findings of the 
LFV, 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.

Explanation of Requirements of Rule

    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, this AD is being issued to prevent excessive 
engine vibration, which could lead to damage of the nacelle structure 
and result in reduced structural integrity and fire shielding 
capability of the nacelle structure, or which could lead to chafing of 
the fire sensor loop and a consequent nuisance fire warning and result 
in a precautionary engine shutdown. This AD requires accomplishment of 
the actions specified in the Saab service bulletin described 
previously, except as discussed below.

Differences Between This Rule and the Service Bulletin

    Operators should note that, although the service bulletin describes 
procedures for a detailed visual inspection of the bottom engine 
vibration isolator if any chafing of the area around the engine is 
detected, this AD requires replacement of the bottom engine vibration 
isolator with a new part if any such chafing is found. The FAA has 
determined that a detailed visual inspection may not provide the degree 
of safety assurance necessary for the transport airplane fleet. The FAA 
finds that continued safety of the transport airplane fleet will be 
better assured by elimination of the source of the problem (i.e., by 
replacing the bottom engine vibration isolator), rather than by an 
inspection. The replacement requirement is in consonance with these 
conditions.
    Operators also should note that, although the service bulletin 
specifies detailed visual inspections of the affected engine mount 
support fitting, adjacent structure, and attaching hardware if any 
engine vibration

[[Page 6524]]

isolator is replaced; the service bulletin does not specify any source 
of service information for corrective actions if any discrepancies are 
found during such inspections. This AD requires any cracked or broken 
part of the engine mount support fitting, adjacent structure, and 
attaching hardware of the bottom, side, and aft engine mount support 
fittings to be repaired prior to further flight in accordance with the 
SAAB 340 Structural Repair Manual.
    Operators also should note that the service bulletin specifies, for 
airplanes on which no chafing is detected during the inspection of the 
area around the engine, a visual inspection of the aft engine vibration 
isolator to determine whether the deflection is within allowable limits 
following replacement of the bottom vibration isolator. However, the 
service bulletin does not specify what actions should be accomplished 
if, during such inspection, the deflection is determined to be outside 
the limits specified in the service bulletin. This AD requires repair 
prior to further flight in accordance with a method approved by the FAA 
or the LFV (or its delegated agent), for airplanes on which no chafing 
is detected, but on which the deflection of the aft engine vibration 
isolator is determined to be outside the limits specified in the 
service bulletin.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 98-NM-373-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    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.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, 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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

99-04-07  Saab Aircraft AB: Amendment 39-11031. Docket 98-NM-373-AD.

    Applicability: Model SAAB SF340A series airplanes, serial 
numbers 004 through 159 inclusive; and Model SAAB 340B series 
airplanes, serial numbers 160 through 453 inclusive; as specified in 
Saab Service Bulletin SAAB 340-71-057, Revision 02, January 26, 
1999, including Attachment 1, dated January 20, 1999; 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 request approval for an 
alternative method of compliance in accordance with paragraph (h) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent excessive engine vibration, which could result in 
damage of the nacelle structure and reduced structural integrity and 
fire shielding capability of the nacelle structure, or which could 
result in chafing of the fire sensor loop and a consequent nuisance 
fire warning and precautionary engine shutdown; accomplish the 
following:
    (a) Within 400 flight hours after the effective date of this AD, 
review the airplane maintenance records to determine the serial 
number of the bottom engine vibration isolator assembly; in 
accordance with Saab Service Bulletin SAAB 340-71-057, Revision 02, 
dated January 26, 1999, including Attachment 1, dated January 20, 
1999.
    (1) If the serial number of the bottom engine vibration isolator 
assembly is listed in Attachment 1 of the service bulletin: Prior to 
further flight, accomplish the requirements of paragraph (b) of this 
AD.
    (2) If the serial number of the bottom engine vibration isolator 
assembly is not listed in Attachment 1 of the service bulletin, and 
the assembly was received new from or overhauled by Barry Controls: 
No further action is required by this AD.
    (3) If the serial number of the bottom engine vibration isolator 
assembly is not listed in Attachment 1 of the service bulletin,

[[Page 6525]]

and was not received new from or overhauled by Barry Controls; or if 
the serial number cannot be identified: Prior to further flight, 
accomplish the requirements of paragraph (c) of this AD.
    (b) For airplanes on which the serial number of the bottom 
engine vibration isolator is determined, during the review of the 
maintenance records required by paragraph (a) of this AD, to be 
listed in Attachment 1, dated January 20, 1999, of Saab Service 
Bulletin SAAB 340-71-057, Revision 02, dated January 26, 1999: Prior 
to further flight, remove the bottom engine vibration isolator and 
perform a one-time visual inspection of the area around the engine 
to detect chafing, in accordance with the service bulletin.
    (1) If no chafing is detected, prior to further flight, install 
a new bottom engine vibration isolator having a molded assembly with 
a cure date other than 9801 through 9825 inclusive, and perform a 
visual inspection of the aft engine vibration isolator to determine 
whether the deflection is within allowable limits, in accordance 
with the service bulletin.
    (i) If the deflection of the aft engine vibration isolator is 
within the limits specified in the service bulletin, no further 
action is required by this AD.
    (ii) If the deflection of the aft engine vibration isolator is 
outside the limits specified in the service bulletin, prior to 
further flight, repair in accordance with a method approved by the 
Manager, International Branch, ANM-116, FAA, Transport Airplane 
Directorate; or the Luftfartsverket (LFV) (or its delegated agent).
    (2) If any chafing is detected, prior to further flight, 
accomplish the requirements of paragraph (e) of this AD.

    Note 2: Inspections and corrective actions accomplished prior to 
the effective date of this AD in accordance with Saab Service 
Bulletin SAAB 340-71-057, dated November 20, 1998; or Revision 01, 
dated December 18, 1998, including Attachment 1, dated December 11, 
1998; are considered acceptable for compliance with the applicable 
actions specified in this amendment.

    (c) For airplanes on which, during the review of the maintenance 
records required by paragraph (a) of this AD, the serial number of 
the bottom engine vibration isolator assembly is determined not to 
be listed in Attachment 1, dated January 20, 1999, of Saab Service 
Bulletin SAAB 340-71-057, Revision 02, dated January 26, 1999; and 
was not received new from or overhauled by Barry Controls; or cannot 
be identified: Prior to further flight, perform a visual inspection 
of the aft engine vibration isolator to determine whether the 
deflection is within allowable limits, and of the area around the 
engine to detect chafing; in accordance with Saab Service Bulletin 
SAAB 340-71-057, Revision 02, dated January 26, 1999, including 
Attachment 1, dated January 20, 1999; and accomplish the 
requirements of paragraph (c)(1), (c)(2), (c)(3), or (c)(4); as 
applicable.
    (1) If the deflection of the aft engine vibration isolator is 
within the limits specified in the service bulletin, if no chafing 
of the area around the engine is detected, and if the bottom engine 
vibration isolator has accumulated 250 flight hours or more: No 
further action is required by this AD.
    (2) If the deflection of the aft engine vibration isolator is 
within the limits specified in the service bulletin, if no chafing 
of the area around the engine is detected, and if the bottom engine 
vibration isolator has accumulated fewer than 250 flight hours: 
Repeat the inspection required by paragraph (b) of this AD one time 
within 250 flight hours after accomplishment of the first inspection 
required by paragraph (b) of this AD.
    (3) If the deflection of the aft engine vibration isolator is 
outside the limits specified in the service bulletin, and if no 
chafing of the area around the engine is detected: Prior to further 
flight, accomplish the requirements of paragraph (d) of this AD.
    (4) If any chafing of the area around the engine is detected: 
Prior to further flight, accomplish the requirements of paragraph 
(e) of this AD.
    (d) For airplanes on which, during the inspection required by 
paragraph (c) of this AD, the deflection of the aft engine vibration 
isolator is determined to be outside the limits specified in Saab 
Service Bulletin SAAB 340-71-057, Revision 02, dated January 26, 
1999, including Attachment 1, dated January 20, 1999; and no chafing 
of the area around the engine is detected: Prior to further flight, 
remove the aft engine vibration isolator, rotate the isolator 180 
degrees, and perform a visual inspection of the snubbers to detect 
damage, in accordance with the service bulletin. Prior to further 
flight, repair any discrepant snubber or replace with a new or 
serviceable snubber, as applicable; reinstall the aft engine 
vibration isolator; and perform a visual inspection of the isolator 
to determine whether the deflection is within allowable limits; in 
accordance with the service bulletin.
    (1) If the deflection of the aft engine vibration isolator is 
within the limits specified in the service bulletin and no chafing 
is detected, no further action is required by this AD.
    (2) If the deflection of the aft engine vibration isolator is 
outside the limits specified in the service bulletin, prior to 
further flight, accomplish the requirements of paragraph (e) of this 
AD.
    (e) For airplanes on which, during the inspection required by 
paragraph (b) or (c) of this AD, any chafing of the area around the 
engine was detected; or for airplanes on which, during the 
inspection required by paragraph (d)(2) of this AD, the deflection 
of the aft engine vibration isolator is determined to be outside the 
limits specified in Saab Service Bulletin SAAB 340-71-057, Revision 
02, dated January 26, 1999, including Attachment 1, dated January 
20, 1999: Prior to further flight, repair any chafing of the area 
around the engine, and replace any discrepant parts with new parts, 
and remove the bottom vibration isolator; in accordance with the 
service bulletin; and, prior to further flight, accomplish the 
requirements of paragraphs (e)(1), (e)(2), (e)(3), and (e)(4) of 
this AD.
    (1) Perform a detailed visual inspection to detect cracked or 
broken parts of the bottom engine mount support fitting, and its 
adjacent structure and attaching hardware, in accordance with the 
service bulletin. Except as provided by paragraph (f) of this AD, 
prior to further flight, repair any cracked or broken part in 
accordance with the SAAB 340 Structural Repair Manual (SRM).
    (2) Install a new bottom vibration isolator having a molded 
assembly with a cure date other than 9801 through 9825 inclusive, in 
accordance with the service bulletin.
    (3) Perform a detailed visual inspection of the side and the aft 
engine vibration isolators for damage, in accordance with the 
service bulletin. If any damage is detected, prior to further 
flight, replace any damaged isolator with a new part, and perform a 
detailed visual inspection to detect cracked or broken parts of the 
affected engine mount support fitting and its adjacent structure and 
attaching hardware, in accordance with the service bulletin. Except 
as provided by paragraph (f) of this AD, if any damage of the 
fittings and adjacent structure is found, prior to further flight, 
repair in accordance with the SRM.

    Note 3: Saab Service Bulletin SAAB 340-71-057, Revision 02, 
references Barry Controls Component Maintenance Manual Section 71-
20-20, dated October 15, 1993, as an additional source of service 
information for accomplishment of the visual inspection of the side 
and aft engine vibration isolators.

    (4) Perform a visual inspection of the aft engine vibration 
isolator to determine whether the deflection is within allowable 
limits, in accordance with the service bulletin.
    (i) If the deflection of the aft engine vibration isolator is 
within the limits specified in the service bulletin, no further 
action is required by this AD.
    (ii) If the deflection of the aft engine vibration isolator is 
outside the limits specified in the service bulletin, accomplish the 
requirements of paragraph (f) of this AD.
    (f) If, during the inspections required by paragraph (e)(1) or 
(e)(3) of this AD, any damage is found that is outside the limits 
specified by the SRM; or if, during the inspection of the aft engine 
vibration isolator required by paragraph (e)(4) of this AD, the 
deflection is outside the limits specified in the service bulletin: 
Prior to further flight, repair in accordance with a method approved 
by the Manager, International Branch, ANM-116, FAA, or the LFV (or 
its delegated agent).
    (g) As of the effective date of this AD, no person shall install 
on any airplane a bottom vibration isolator molded assembly having 
P/N 00-13226-03 and a cure date 9801 through 9825 inclusive.
    (h) 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, International Branch, ANM-116. 
Operators shall submit their requests through an appropriate FAA 
Principal Maintenance Inspector, who may add comments and then send 
it to the Manager, International Branch, ANM-116.

    Note 4: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be

[[Page 6526]]

obtained from the International Branch, ANM-116.

    (i) 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.
    (j) Except for the repair actions as provided by paragraphs 
(b)(1)(ii), (e)(1), (e)(3), and (f) of this AD, the actions shall be 
done in accordance with Saab Service Bulletin SAAB 340-71-057, 
Revision 02, dated January 26, 1999, including Attachment 1, dated 
January 20, 1999, which contains the following list of effective 
pages:

------------------------------------------------------------------------
                                    Revision
                                      level
             Page No.               shown on      Date shown on page
                                      page
------------------------------------------------------------------------
1-5...............................        02  Jan. 26, 1999.
           Attachment 1
1-10..............................      None  Jan. 20, 1999.
------------------------------------------------------------------------

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, SAAB Aircraft 
Product Support, S-581.88, 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.

    Note 5: The subject of this AD is addressed in Swedish 
airworthiness directive SAD 1-135R1, dated December 18, 1998.

    (k) This amendment becomes effective on February 25, 1999.

    Issued in Renton, Washington, on February 2, 1999.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-3033 Filed 2-9-99; 8:45 am]
BILLING CODE 4910-13-U