AD Amdt-39-9480

[Federal Register Volume 61, Number 5 (Monday, January 8, 1996)]
[Rules and Regulations]
[Pages 511-513]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 96-188]



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Federal Register / Vol. 61, No. 5 / Monday, January 8, 1996 / Rules 
and Regulations

[[Page 511]]


DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-260-AD; Amendment 39-9480; AD 96-01-04]


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 revising the Airplane Flight Manual 
(AFM) to require verification that the auto-ignition system is 
operational; to define icing conditions at higher ambient temperatures; 
and to provide the flight crew with limitations and procedures to aid 
in the avoidance of engine power interruptions. This amendment is 
prompted by a report of complete power loss of the left engine and 
power fluctuations on the right engine as a result of build up of ice 
and/or slush in the engine inlet and subsequent ingestion into the 
engines; the auto-ignition system of the left engine had failed, which 
prevented automatic restart of the engine following power interruption. 
The actions specified in this AD are intended to prevent failure of the 
auto-ignition system to re-light the engine in the event of power 
interruptions due to the ingestion of ice and/or slush into the engine, 
which could result in engine flameout and subsequent shutdown, and to 
provide the flight crew with guidance to aid in avoidance of such 
occurrences.

DATES: Effective January 23, 1996.
    Comments for inclusion in the Rules Docket must be received on or 
before March 8, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-260-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.
    The information concerning this amendment may be obtained from or 
examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, 
SW., Renton, Washington.

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: The FAA has received a report indicating 
that an unsafe condition may exist on certain Saab Model SAAB SF340A 
and SAAB 340B series airplanes. Recently, an incident occurred on a 
Model SAAB 340B series airplane during which, shortly after exiting 
icing conditions, the left engine of the airplane shut down abruptly 
and the right engine experienced multiple power interruptions.
    Subsequent investigation revealed that shutdown of the left engine 
occurred due to ingestion of ice and/or slush into the engine from the 
inlet. In addition, the auto-ignition system had failed on that engine; 
therefore, engine re-light did not occur. Failure of the auto-ignition 
system, which is a component of the engine Digital Electronic 
Controller (DEC), was the result of a broken fuse. This fuse failure 
also caused the engine turbine (or Np) overspeed protection system to 
be inoperative.
    The interruptions of power to the right engine also were caused by 
ingestion of ice and/or slush into the engine; however, the auto-
ignition system for the right engine was operational and engine re-
light occurred. In addition, failure of the auto-ignition system can 
exist concurrently such that engine re-light does not occur. These 
conditions, if not corrected, could result in engine flameout and 
subsequent shutdown.
    Although single event power interruptions have occurred previously 
on this airplane type, recent occurrences of multiple power 
interruptions demonstrate a need to increase the safety margin for 
flight in icing conditions. Activation of the engine anti-icing system 
at higher ambient temperatures will reduce the ice/slush build-up 
within the engine inlet and will improve the engine surge margin.
    In light of the information discussed previously, the FAA finds 
that certain limitations and procedures should be included in the FAA-
approved Airplane Flight Manual (AFM) to:

--provide the flight crew with procedures to verify that the auto-
ignition system is operational;
--expand the current definition of icing conditions by increasing the 
temperature at which those conditions exist from +5 degrees Celsius to 
+10 degrees Celsius; and
--alert the flight crew to certain icing conditions during which power 
to an engine may be interrupted, and provide the flight crew with 
guidance to aid in avoidance of such occurrences.

    The FAA has determined that such limitations and procedures 
currently are not defined adequately in the AFM for these airplanes.
    This airplane model is manufactured in Sweden and is 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 Luftfartsverket (LFV), which is 
the airworthiness authority for Sweden, 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.
    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 failure of the 
auto-ignition system to re-light the engine in the event of power 
interruptions due to the ingestion of ice and/or slush into the engine, 
which could result in engine flameout and subsequent shutdown; and 

[[Page 512]]
to provide the flight crew with guidance to aid in avoidance of such 
occurrences.
    This AD requires the following:

--revising the Limitations Section of the AFM to require verification 
that the auto-ignition system is operational;
--revising the Limitations Section of the AFM to define icing 
conditions at higher ambient temperatures;
--revising the Normal Procedures Section of the AFM to alert the flight 
crew to certain icing conditions during which power to an engine may be 
interrupted, and to provide the flight crew with limitations and 
procedures to aid in avoidance of interruptions of power to an engine.

    For Model SAAB 340B series airplanes having an auto-ignition system 
that is found to be inoperative, this AD requires a test of the Np 
overspeed system to ensure that it is operative, and repair, if 
necessary.
    This is considered to be interim action until final action is 
identified, at which time the FAA may consider further rulemaking.
    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 95-NM-260-AD.'' The postcard will be date stamped and 
returned to the commenter.
    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, 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 USC 106(g), 40101, 40113, 44701.


Sec. 39.13  [Amended]

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

96-01-04 SAAB Aircraft AB: Amendment 39-9480. Docket 95-NM-260-AD.

    Applicability: Model SAAB SF340A series airplanes, serial 
numbers 004 through 159 inclusive; and Model SAAB 340B series 
airplanes, serial numbers 160 and subsequent; 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 use the authority 
provided in paragraph (c) of this AD to request approval from the 
FAA. This approval may address either no action, if the current 
configuration eliminates the unsafe condition; or different actions 
necessary to address the unsafe condition described in this AD. Such 
a request should include an assessment of the effect of the changed 
configuration on the unsafe condition addressed by this AD. In no 
case does the presence of any modification, alteration, or repair 
remove any airplane from the applicability of this AD.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the auto-ignition system to re-light the 
engine in the event of power interruptions due to the ingestion of 
ice and/or slush into the engine, which could result in engine 
flameout and subsequent shutdown; and to provide the flight crew 
with guidance to aid in avoidance of such occurrences; accomplish 
the following:
    (a) Within 10 days after the effective date of this AD, revise 
the FAA-approved Airplane Flight Manual (AFM) to include the text 
contained in paragraphs (a)(1), (a)(2), (a)(3), and (a)(4) of this 
AD, as applicable. This may be accomplished by inserting a copy of 
this AD into the AFM.
    (1) For Model SAAB SF340A series airplanes: Insert the following 
sub-section in the Limitations Section of the AFM:

``IGNITION SYSTEM

    Prior to each flight, before engine start, perform a check of 
the auto-ignition system.
    <bullet> Select batteries ON (external power ON or OFF).
    <bullet> Check that IGN switches are in NORM position.
    <bullet> Advance PLs above FLT IDLE and verify the IGN lights in 
the Flight Status Panel (FSP) illuminate. In bright sunlight, shade 
FSP to ensure IGN lights are visible when illuminated.
    <bullet> Retard PLs to GND IDLE. (IGN lights should go out.)
    <bullet> If an IGN light fails to illuminate when PLs are above 
FLT IDLE, the auto-ignition system is considered to be inoperative.
    If the auto-ignition system is inoperative:
    <bullet> BEFORE ENTERING ICING CONDITIONS, SET IGNITION TO CONT. 
Maintain ignition in CONT until touchdown, even if icing conditions 
cease to exist.''

[[Page 513]]

    (2) For Model SAAB 340B series airplanes: Insert the following 
sub-section in the Limitations Section of the AFM:

``IGNITION SYSTEM

    After each engine shutdown, perform a check of the auto-ignition 
system.
    <bullet> Adjust Ng to approximately 75%-77%; minimum is 75%.
    <bullet> Shut down the engines (CL to FUEL OFF).
    <bullet> Verify the IGN lights in the Flight Status Panel (FSP) 
illuminate while Ng is above 62%. In bright sunlight, shade the FSP 
to ensure that lights are visible when illuminated.
    <bullet> If an IGN light fails to illuminate, the auto-ignition 
system is considered to be inoperative.
    <bullet> Retard PLs to GND IDLE.
    If the auto-ignition system is inoperative:
    <bullet> BEFORE ENTERING ICING CONDITIONS, SET IGNITION TO CONT. 
Maintain ignition in CONT until touchdown, even if icing conditions 
cease to exist.''
    (3) For all airplanes: Insert the following in the Limitations 
Section of the AFM, under Icing Conditions:
    ``Icing conditions exist when visible moisture in any form is 
present (such as clouds, fog with visibility of one mile or less, 
rain, snow, sleet, ice crystals) or standing water, slush, or snow 
(hard packed snow excluded) is present on the ramps, taxiways, or 
runways and the OAT or SAT is +10 degrees C and below during ground 
and flight operation.''
    (4) For all airplanes: Insert the following in the Normal 
Procedures Section of the AFM, under Operation in Icing Conditions:

``CAUTION

    Engine power interruptions may occur at ISA to ISA +20 degrees 
Celsius temperature and in light (or undetected) icing conditions, 
or shortly after exiting these conditions. Engine function will 
normally be recovered by the auto-ignition system before any serious 
loss of power. To aid in avoidance of these occurrences:
    <bullet> Engine anti-ice systems must be activated prior to 
entering icing conditions, and maintained ON for at least 5 minutes 
after exiting icing conditions.''
    (b) For Model SAAB 340B series airplanes: If an auto-ignition 
system is found to be inoperative, prior to further flight, perform 
an Np overspeed test to ensure that the Np overspeed system is 
operative, in accordance with the procedures specified in General 
Electric Maintenance Manual SEI-576. If the Np overspeed system is 
found to be inoperative, prior to further flight, repair in 
accordance with the procedures specified in General Electric 
Maintenance Manual SEI-576.
    (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 2: 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) This amendment becomes effective on January 23, 1996.

    Issued in Renton, Washington, on January 2, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-188 Filed 1-5-96; 8:45 am]
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