[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 [www.gpo.gov]
[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
