[Federal Register Volume 61, Number 170 (Friday, August 30, 1996)]
[Rules and Regulations]
[Pages 45880-45883]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-22009]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 95-NM-243-AD; Amendment 39-9727; AD 96-18-03]
RIN 2120-AA64
Airworthiness Directives; Saab Model SAAB 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 SAAB SF340A and SAAB 340B series
airplanes, that requires installation of an automatic flight idle stop
on the control quadrant in the flight compartment. This amendment is
prompted by several reports of one or both power levers being moved aft
of the flight idle stop on approach. The actions specified by this AD
are intended to prevent such movement of the power lever(s) during
flight, which could result in the loss of power to one or both engines,
as well as severe engine damage.
DATES: Effective October 4, 1996.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of October 4, 1996.
ADDRESSES: 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
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: Ruth E. Harder, Aerospace Engineer,
Standardization Branch, ANM-113, FAA, Transport Airplane Directorate,
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206)
227-1721; fax (206) 227-1149.
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 SAAB SF340A and
SAAB 340B series airplanes was published in the Federal Register on
March 21, 1996 (61 FR 11591). That action proposed to require
installation of an automatic flight idle stop on the control quadrant
in the flight compartment.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received.
Support for the Proposal
One commenter supports the proposal in its entirety.
Request To Extend Compliance Time
Two commenters request that the compliance time for the
installation be extended beyond the proposed 12 months. One commenter
suggests that the compliance time be extended to 18 months so that the
installation may be performed during a regularly scheduled maintenance
interval. This would preclude additional costs incurred from special
scheduling and additional downtime. The other commenter requests that
the compliance time be extended to 20 months because the current number
of available parts and the vendors turnaround time for delivery of
parts will not be able to support the modification of the entire U.S.
fleet of 230 airplanes within 12 months.
The FAA does not concur with the commenters request. In developing
a compliance time for this AD action, the FAA considered not only the
degree of urgency associated with addressing the subject unsafe
condition, but:
1. the recommendations for compliance time specified by the
Luftfartsverket (LFV), which is the airworthiness authority for Sweden,
and by the manufacturer;
2. the availability of required parts; and
3. the practical aspect of installing the required modification
within an interval of time that parallels normal scheduled maintenance
for the majority of affected operators.
Based on information received from the manufacturer relative to
parts availability and vendor turnaround time, the FAA considers that
the 12-month compliance time is adequate if operators make reasonable
efforts to meet this schedule. However, under the provisions of
paragraph (c) of the final rule, the FAA may approve requests for
[[Page 45881]]
adjustments to the compliance time if data are submitted to
substantiate that such an adjustment would provide an acceptable level
of safety.
Request To Reference Latest Revision to Service Information
One commenter requests that the proposal be revised to cite the
latest revisions to the SAAB service bulletins as the appropriate
source of service information.
The FAA concurs with the commenters request. Since issuance of the
notice, SAAB has issued the following revisions to the referenced
service documents:
1. Service Bulletin 340-76-031, Revision 4, dated February 25,
1996.
2. Service Bulletin 340-76-032, Revision 3, dated March 25, 1996.
3. Service Bulletin 340-32-100, Revision 2, dated March 25, 1996.
These revised service bulletins are essentially identical to
previous versions, but contain various minor editorial corrections and
updated cost figures. They do not affect modifications that were
accomplished in accordance with earlier versions of these service
bulletins.
The FAA has revised the final rule to cite the latest versions of
the service bulletins and has added information to specify that
previous accomplishment of the installation in accordance with any
earlier version of the service bulletin is acceptable for compliance
with the applicable parts of the rule.
Request To Allow Continued Flight with Flight Idle Stop Inoperative
One commenter requests that the proposal be revised to provide
relief from the Master Minimum Equipment List (MMEL) provisions to
allow the airplane to continue to be operated if the flight idle (FI)
stop is inoperative. In support of this request, the commenter points
out that the Model SF340 automatic FI stop is unique in that, once the
override mechanism is activated, the system cannot be reset without
maintenance intervention. The commenter requests that the proposed AD
allow affected operators to operate the airplane for at least a single
additional revenue flight to a maintenance base where the FI system can
be reset (or repaired, if necessary). Such relief would preclude what
the commenter considers ``an unreasonable exposure to loss of service''
following such overrides.
The FAA concurs. In the event of a malfunction of the FI stop
system, use of the FI stop override function is available to the flight
crew. However, due to the redundant system design of the FI stop, the
necessity for use of the override is expected to be very rare. In any
case where the automatic system has malfunctioned and/or use of the
override has been necessary, as the commenter correctly notes,
maintenance action is required to return the FI stop system to an
operational condition. If adequate maintenance support is not available
upon landing, the FAA has determined that the airplane may be operated
safely for one revenue flight to a location where appropriate
maintenance can be performed, provided that the FI stop system has been
properly deactivated and placarded for flight crew awareness in
accordance with the provisions of the FAA-approved MMEL. A new
paragraph has been added to the final rule to specify this.
Request To Allow Continued Flight if Anti-Skid System is
Inoperative
This same commenter requests that the proposal be revised to
provide MMEL relief to allow dispatch of an airplane equipped with an
automatic FI stop system when the anti-skid system is inoperative. The
commenter states that, while the quadruple redundancy of the
``release'' signal to the FI stop solenoid will minimize system faults
that cause the solenoid to not release, this redundancy will result in
the inability to defer the anti-skid system.
The FAA does not consider that additional revision of the proposed
rule is necessary. The FI stop system uses wheel-spin-up signals from
the anti-skid system to drive the FI stop to the open position. Other
signals, such as weight-on-wheels signals, are also used to drive the
FI stop to the open position, thus providing a redundant system design
of the FI stop. However, the Abnormal Procedures specified in the FAA-
approved Airplane Flight Manual (AFM) that relate to in-flight failure
of the anti-skid system may include instructions for the flight crew to
activate override of the FI stop upon landing. This use of the FI stop
override then requires maintenance action to reset and, as discussed in
the previous issue, the FAA has determined that a single flight for
return of the aircraft to a location for maintenance will meet
acceptable safety levels. Since the most restrictive requirements take
precedence in the determination of dispatch relief, other equipment,
such as the anti-skid system, may also be required to be repaired to
support the requirements for the FI stop system.
Request To Provide Flight Crew With Indication of Status of FI
System
One commenter supports the intent of the proposal, but requests
that it be revised to include a requirement to provide the flight crew
with adequate indication of the system status and failure annunciation,
as well as a means to verify that the system is operational while in
flight. The commenter considers that a status indicator is required to
inform the flight crew of the mode of the lockout system. As a minimum,
this indicator should inform the crew of two conditions:
1. the system has experienced a failure of some type, and
2. ground idle will not be available when it should be.
This commenter also considers that a means is necessary to allow
the crew to test (fault check) and verify the system status and
operability. Accurate knowledge of the system's status can be critical
to the safety of the operation.
The FAA concurs partially with the commenter's statements about the
need for adequate status indication and crew verification. The
automatic FI stop system has been designed to provide status indication
to the flight crew. The position of the FI stop in either the ``open''
position (no blocking of power levers into beta) or ``closed'' position
is provided by means of indications on the top of the Flight Status
Panel (FSP) as follows:
FI stop (blue): FI stop is open and landing gear is down
and locked. This is the normal indication when the airplane is
electrically powered on the ground. The blue light normally will turn
off when the landing gear is retracted after takeoff, and it does not
illuminate for the duration of the flight. If the landing gear is not
retracted following takeoff, the light will stay on, and the FI stop
will remain open, until all wheels have spun down to less than 9 knots,
which may take up to 90 seconds.
FI stop open (amber): This light indicates an abnormal
situation, showing that the FI stop is open, although landing gear is
not down and locked. The amber light will appear if the FI stop fails
to close after takeoff when the landing gear is retracted, indicating
that there is no protection against movement of the power levers into
beta during flight. This light also will appear if the manual override
knob is pulled, causing the FI stop to open. This status indication is
intended to alert the flight crew when FI stop protection is not
available; therefore, increased crew awareness is necessary to prevent
inadvertent placement of the
[[Page 45882]]
power levers into beta mode during flight.
These status indications do not, however, predict an upcoming
failure of the FI stop to open correctly upon landing. Due to the
redundant system design of the FI stop, and based on the failure
analysis probabilities, malfunction of the FI stop system that would
result in the system remaining closed after touchdown is predicted to
be very infrequent. In the event of a malfunction or if adverse runway
conditions result in the FI stop remaining closed upon touchdown, the
override mechanism is always available to the flight crew. Operators
may refer to SAAB 340 Operations Bulletin No. 52, which describes
procedures to be followed in such an event.
As for the commenter's request for a means to allow the flight crew
to test (fault check) and verify the system status and operability, the
FAA points out that the FI stop lights on the FSP, as described above,
provide an accurate indication of the system operation; in light of
this, the FAA does not consider it necessary to add a flight crew test
in addition to this status information. Additionally, lamp checks may
be performed by the flight crew to ensure that the FI stop indication
lights themselves are operational.
Request To Include Provisions To Minimize Compound System Failures
The same commenter requests that the proposal be revised to include
provisions to minimize or exclude compound systems failures, and to
ensure that the flight crew is able to override the automatic system if
it becomes necessary to do so. If these features are not available, the
commenter requests that the FI stop system be changed to incorporate
them. To support its request, the commenter states that provisions must
be made to eliminate failure modes that would result in certain systems
being simultaneously disabled. The primary concern is the
controllability of the airplane on the ground. Inability to select
ground idle after landing may seriously degrade the airplane's stopping
performance. If a failure that prevents access to ground idle also
disables other ground operation related systems (such as nose wheel
steering), the stopping capability and/or the controllability of the
airplane could be seriously compromised. In order to further improve
the reliability and independence of the FI stop installation, this
commenter urges incorporation of three specific design considerations:
1. the ability to tap the spin-up signal in its rawest usable form,
prior to it being processed by any digital/control component, to avoid
its loss if that component should fail;
2. a redundant, parallel spin-up signal provided in case of a
failure or lack of signal from one sensor;
3. a revision to the system operation that will address the
possibility of reduced wheel spin-up (i.e., hydroplaning).
Related to the possibility of such failures, this commenter also
states that provisions must be made to enable the flight crew to
deliberately and rapidly override the FI stop system. This is necessary
to prevent a system failure from creating a potentially hazardous
situation when the crew is attempting to stop the airplane. The
commenter states that, if power cannot be reduced below flight idle
during the landing roll-out, the stopping capability of the airplane
will be significantly degraded, potentially resulting in a runway
overrun.
The FAA concurs with this commenter's statements, but finds that no
revision to the rule is necessary because the design features suggested
by the commenter already have been incorporated into the FI stop
system. The quadruple redundancy of the ``release'' signal to the FI
stop solenoid has been designed in order to minimize system faults that
would cause the solenoid to not release. If the left or right landing
gear is extended, and if any one of the left or right inboard or
outboard wheel speed signals is greater than 25 knots, or if the left
or right weight-on-wheels signal is true, then the FI stop system is
opened, permitting unrestricted movement of the power levers.
Additionally, in the unlikely event that this combination of data
fails to drive the FI stop to the ``open'' position, a manual override
knob is also available to the flight crew. When this override knob is
pulled, the FI stop will be mechanically forced to the ``open''
position. This combination of the redundant signal inputs and the
override knob was intentionally designed into the FI stop system to
enable selection of beta modes when necessary for slowing action.
Conclusion
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.
Cost Impact
The FAA estimates that 224 airplanes of U.S. registry will be
affected by this proposed AD. Accomplishment of the required
installations will take between 122 and 142 work hours per airplane,
depending upon the configuration of the airplane. The average labor
rate is $60 per work hour. Required parts will cost approximately
$9,300 per airplane. Based on these figures, the cost impact of this AD
on U.S. operators is estimated to be between $3,722,880 and $3,991,680
(or between $16,620 and $17,820 per airplane).
The 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.
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.
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:
[[Page 45883]]
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:
96-18-03 Saab Aircraft AB: Amendment 39-9727. Docket 95-NM-243-AD.
Applicability: Model SAAB SF340A series airplanes, serial
numbers -004 through -159 inclusive; and Model SAAB 340B series
airplanes, serial numbers -160 through -379 inclusive; 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 (c) 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 the movement of both power levers aft of the flight
idle stop during flight, which could result in loss of power to both
engines, as well as severe engine damage, accomplish the following:
(a) Within 12 months after the effective date of this AD,
accomplish the requirements of paragraphs (a)(1), (a)(2), and (a)(3)
of this AD.
Note 2: The actions specified in paragraphs (a)(1) and (a)(2) of
this AD may be accomplished prior to, or in conjunction with, the
accomplishment of the requirement of paragraph (a)(3) of this AD.
(1) Modify the electrical system of the flight idle stop in
accordance with Saab Service Bulletin 340-76-031, Revision 04, dated
February 25, 1996.
Note 3: Accomplishment of this modification prior to the
effective date of this AD in accordance with previous revisions of
Saab Service Bulletin 340-76-031 is considered acceptable for
compliance with this paragraph.
(2) Install a control unit with a wheel spin-up signal in
accordance with Saab Service Bulletin 340-32-100, Revision 02, dated
March 25, 1996.
Note 4: Accomplishment of this installation prior to the
effective date of this AD in accordance with previous revisions of
Saab Service Bulletin 340-32-100 is considered acceptable for
compliance with this paragraph.
(3) Install an automatic flight idle stop on the control
quadrant in the flight compartment in accordance with Saab Service
Bulletin 340-76-032, Revision 03, dated March 25, 1996.
Note 5: Accomplishment of this installation prior to the
effective date of this AD in accordance with previous revisions of
Saab Service Bulletin 340-76-032 is considered acceptable for
compliance with this paragraph.
Note 6: Paragraph 2.A. of the Accomplishment Instructions of
Saab Service Bulletin 340-76-032 specifies procedures for removal of
a mechanical beta stop mechanism from the airplane. Since
installation of a mechanical beta stop mechanism was not previously
required for all airplanes by AD, that mechanism may not have been
installed on certain airplanes affected by this AD. In such cases,
procedures for removal of the mechanical beta stop would not apply.
(b) In cases where the automatic flight idle (FI) stop has
malfunctioned and/or use of the FI stop override has been necessary,
the airplane may be operated for one revenue flight to a location
where required maintenance/repair can be performed, provided that
the FI stop system has been properly deactivated and placarded for
flight crew awareness in accordance with the provisions of the FAA-
approved Master Minimum Equipment List (MMEL).
(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 7: 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 modification and installations shall be done in
accordance with Saab Service Bulletin 340-76-031, Revision 04, dated
February 25, 1996; Saab Service Bulletin 340-32-100, Revision 02,
dated March 25, 1996; and Saab Service Bulletin 340-76-032, Revision
03, dated March 25, 1996. 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.
(f) This amendment becomes effective on October 4, 1996.
Issued in Renton, Washington, on August 21, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 96-22009 Filed 8-29-96; 8:45 am]
BILLING CODE 4910-13-U
