AD 96-01-04 Airworthiness Directives; Saab Model SAAB SF340A and SAAB 340B Series Airplanes

Models named: SAAB SF340A series, SAAB 340B series. Read the applicability below — it usually turns on serial or part numbers too.

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.

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. Select batteries ON (external power ON or OFF). Check that IGN switches are in NORM position. 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. Retard PLs to GND IDLE. (IGN lights should go out.) 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: 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. Adjust Ng to approximately 75%-77%; minimum is 75%. Shut down the engines (CL to FUEL OFF). 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. If an IGN light fails to illuminate, the auto-ignition system is considered to be inoperative. Retard PLs to GND IDLE. If the auto-ignition system is inoperative: 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: 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] BILLING CODE 4910-13-U