# Service Bulletin

11 July 2014 

# 340–27–121

Page 1 of 24 

# ATA CHAPTER: 27 FLIGHT CONTROLS – STALL WARNING/IDENTIFICATION SYSTEM – ACTIVATION OF IMPROVED STALL WARNING SYSTEM FOR ICING CONDITION (BASIC WINGTIP)
Mod No. 3529

1. PLANNING INFORMATION

A. EFFECTIVITY (1) Aircraft: Aircraft Mfg. Serial No’s SAAB SF340A – 004–159.
Aircraft Mfg. Serial No’s SAAB 340B – 160–169, 171–341, 343–361, 364–366, 368–371, 373–378, 380–384, 386–394, 396–404, 406–408, 410–430, 432–454, 456–459.
NOTE : Service Bulletin SAAB 340–27–109 (Mod No 3311, 3528, 3542) or Service Bulletin SAAB 340–27–120 (Mod No 3311, 3528) must be included before or in conjunction with this Service Bulletin. (A/C POST Service Bulletin SAAB 340–27–120 includes A/C both PRE and POST SB340–27–097, and both PRE and POST SB340–27–116)
NOTE : This Service Bulletin supersedes and cancels Service Bulletin SAAB340–27–098.
NOTE : This Service Bulletin is applicable for A/C with Basic Wingtip: (A/C with Basic Wingtip are A/C PRE Service Bulletin SAAB340–57–026 and PRE Service Bulletin SAAB340–57–030 and without Option 57:01)
NOTE : Implementation of this Service Bulletin require changes to procedures and performance when Engine Anti–Ice is used. (2) Spares: Not affected.

B. REASON Natural stall has in few cases been experienced in icing condition before stall warning. In order to prevent such unsafe condition a modified stall warning system has been developed. This Service Bulletin installs the new stall warning computers and activates the modified stall warning system that includes stall warning curves that are optimized for operation in icing conditions. The ice compensated stall warning curves are activated by selection of Engine Anti Ice.

C. DESCRIPTION This Service Bulletin gives instructions for: – removal of panels for access – removal of the existing stall warning computers – removal of blank label or INOP label, at the push button switch 3WHC – removal of shrinkable tubing and/or cable–tie at the circuit breaker 2WHC – installation and/or activation of the circuit breaker 2WHC – installation of labels for the push button switch 3WHC and for the circuit breaker 2WHC – connection of parked and stowed wires – installation of the new stall warning computers – installation of the removed access panels – functional test of the stall warning system.

D. COMPLIANCE Mandatory

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# 340–27–121

Page 2 of 24 Saab recommends this Service Bulletin to be performed within 18 months from release of this Service Bulletin.
This Service Bulletin is under EASA consideration for an Airworthiness Directive. The final compliance terms will be set by the EASA Airworthiness Directive (AD) when issued.

E. APPROVAL This Service Bulletin is developed and approved under the authority of DOA nr. EASA.21J.066. The change addressed in the bulletin is classified as ”Major” in accordance with EC regulation 748/2012 Part 21A.91 and is approved by the European Aviation Safety Agency. Ref. EASA No. 10049287.

F. MANPOWER Estimated time to complete this Service Bulletin is: 2 persons required for the test procedure.
Total manhours: 8 Elapsed time (hours): 4 Labour cost at operators expense.

G. MATERIAL – COST AND AVAILABILITY Price and availability for Mod Kit. No. SAAB 340–27–121–01 will be furnished on request.

H. TOOLING (1) Insert tool M81969/14–01, use for insert of contacts/wires to 3WH–P1 and 4WH–P1. (2) Angle of attack (AOA) calibration tools: – TES–4054332–001 (LH) – TES–4054332–002 (RH). (3) Weight on wheels (WOW) switches operating tool, TDO 5–4650224.

I. WEIGHT AND BALANCE
None.

J. ELECTRICAL LOAD DATA RH Bat Bus: +170 mA when ice compensated stall warning curves are active. LH Main Bus: +60 mA when ice compensated stall warning curves are active. RH Main Bus: +60 mA when ice compensated stall warning curves are active. RH Bat Bus: +60 mA when lamps are in DIM mode. RH Bat Bus: +60 mA when weight on wheel is true.

K. REFERENCES
Aircraft Maintenance Manual (AMM) 06–30–00 Description / Operation 12–00–00 Servicing 24–00–00 Maintenance practice

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# 340–27–121

Page 3 of 24 27–35–10 Removal / Installation 39–10–42 Maintenance practice

Wiring Manual (WM) 20–00–00 Standard practices

L. OTHER PUBLICATIONS AFFECTED
Aircraft Maintenance Manual (AMM) Illustrated Parts Catalog (IPC) Wiring Manual (WM) Airplane Flight Manual (AFM) Aircraft Operations Manual (AOM) Master Minimum Equipment List (MMEL) Minimum Equipment List Procedures Guide (MELPG)

2. ACCOMPLISHMENT INSTRUCTIONS

A. JOB SET–UP (1) Before you start the SB, make sure: – The modification kit contains the parts listed in the Service Bulletin – The local supply items listed in the Service Bulletin are available – The documentation is available – The special tools are available. (2) Make the aircraft safe for maintenance: (a) Isolate the electrical power (Ref. AMM 24–00–00, maintenance practices). (3) Open for access: REF. FIG. 1, 2 and 3
FOR A/C 004–078 (a) At the avionics rack, remove the access panel 210AZ (Ref. AMM 06–30–00).
FOR A/C 079–459 (b) At the avionics rack, remove the access panel 220AZ (Ref. AMM 06–30–00).
FOR A/C ALL (c) In the flight compartment, loosen the screws that attach the circuit breaker panel 10VU to the structure and lower the panel.
FOR A/C PRE SB340–27–109, or FOR A/C PRE SB340–27–116 and POST SB340–27–120 (d) In the flight compartment, loosen the screws that attach the circuit breaker panel 12VU to the structure and lower the panel.
FOR A/C ALL

B. REMOVAL (1) Removal of the stall warning computers
REF. FIG. 1 (a) Remove the stall warning computer 3WH (110) (Ref. AMM 27–35–10).

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Page 4 of 24 (b) Remove the stall warning computer 4WH (110) (Ref. AMM 27–35–10).

C. MODIFICATION
CAUTION : BE CAREFUL WHEN YOU DO THE MODIFICATION OF THE HARNESS. MAKE SURE THAT YOU DO NOT DAMAGE THE EXISTING WIRES WHEN NEW WIRES ARE INSTALLED. CLEAN AND INSPECT THE AFFECTED HARNESS WHEN THE MODIFICATION IS COMPLETED. DAMAGES TO THE WIRES CAN CAUSE SYSTEM MALFUNCTION.
NOTE : All wiring changes are to be performed in accordance with the procedures in the WM 20–00–00.
FOR A/C PRE SB340–27–109, or FOR A/C PRE SB340–27–116 and POST SB340–27–120 (1) Activation of the push button switch 3WHC
REF. FIG. 2 (a) At the instrument panel 1VU, remove the blank label (R112) from the push button switch 3WHC. (b) At the instrument panel 1VU, install the label (12) ”ICE SPD CANCEL” above the push button switch 3WHC. (2) Installation of the circuit breaker 2WHC
REF. FIG. 2 (a) Find the stowed circuit breaker 2WHC behind the circuit breaker panel 12VU. (b) Carefully remove the shrinkable tubing from the circuit breaker 2WHC. (c) At the RH circuit breaker panel 12VU, remove the cover (R115) from position S–28. (d) At the RH circuit breaker panel 12VU, install the circuit breaker 2WHC at position S–28 (Ref. AMM 39–10–42). (e) Remove the cable–tie and close the circuit breaker 2WHC. (f) At the RH circuit breaker panel 12VU, install the label (13) ”SW ICE IND” at position S–28.
FOR A/C POST SB340–27–109, or FOR A/C POST SB340–27–116 and POST SB340–27–120 (3) Activation of the push button switch 3WHC
REF. FIG. 3 (a) At the instrument panel 1VU, remove the INOP label from the location adjacent to the push button switch 3WHC. (b) If applicable, (if the ”ICE SPD CANCEL” label is missing or is defective), install the label (12) ”ICE SPD CANCEL” above the push button switch 3WHC. (4) Activation of the circuit breaker 2WHC
REF. FIG. 3 (a) On the RH circuit breaker panel 12VU at the position S–28, remove the cable–tie and close the circuit breaker 2WHC. (b) If installed, remove the INOP label from the position S–28. (c) If applicable, (if the ”SW ICE IND” label is missing or is defective), install the label (13) ”SW ICE IND” at 12VU position S–28.

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Page 5 of 24 FOR A/C ALL (5) Connection of parked and stowed wires REF. FIG. 1, 2 and 3 (a) At (behind) the circuit breaker panel 10VU, find the stowed wire WHC36–16 adjacent to the circuit breaker 36WH. (b) Carefully remove the shrinkable tubing from the wire and from the terminal lug. (c) Connect this wire:
FOR A/C 004–078
REF. FIG. 4 and 6
FOR A/C 079–459
REF. FIG. 5 and 7
FOR A/C ALL

Wire No: Class: From: Contact: To: Contact: Remarks:
WHC36–16 A 36WH:911 36WH:L/1

FOR A/C 004–078 (d) In the avionics rack, find these four stowed wires adjacent to 3WH–P1 and 4WH–P1. – WHC16–24 – WHC17–24 – WHC18–24 – WHC39–24 (e) Carefully remove the shrinkable tubing from the four wires and from the contacts. (f) Connect these wires:
REF. FIG. 4 and 6

Wire No: Class: From: Contact: To: Contact: Remarks:
WHC16–24 A 4WH–P1:911 4WH–P1:7
WHC17–24 A 3WH–P1:911 3WH–P1:7
WHC18–24 A 4WH–P1:911 4WH–P1:15
WHC39–24 A 3WH–P1:911 3WH–P1:15

FOR A/C 079–459 (g) In the avionics rack, find these four stowed wires adjacent to 3WH–P1 and 4WH–P1. – WHC44–24 – WHC45–24 – WHC46–24 – WHC47–24 (h) Carefully remove the shrinkable tubing from the four wires and from the contacts. (i) Connect these wires:
REF. FIG. 5 and 7

Wire No: Class: From: Contact: To: Contact: Remarks:
WHC44–24 A 4WH–P1:911 4WH–P1:15
WHC45–24 A 4WH–P1:911 4WH–P1:7

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Page 6 of 24 Wire No: Remarks: Contact: To: Contact: From: Class:
WHC46–24 A 3WH–P1:911 3WH–P1:15
WHC47–24 A 3WH–P1:911 3WH–P1:7

FOR A/C ALL

D. INSTALLATION (1) Installation of the new stall warning computers
REF. FIG. 1 (a) Install the stall warning computer 3WH (10) (Ref. AMM 27–35–10). (b) Install the stall warning computer 4WH (10) (Ref. AMM 27–35–10). (2) In the flight compartment: (a) Put the circuit breaker panel 10VU in position at the structure and tighten the screws.
FOR A/C PRE SB340–27–109, or FOR A/C PRE SB340–27–116 and POST SB340–27–120 (b) Put the circuit breaker panel 12VU in position at the structure and tighten the screws.
FOR A/C ALL

E. FUNCTIONAL TEST (1) Prepare the aircraft for test:
CAUTION : BE CAREFUL WHEN YOU MOVE THE VANES. MOVE THE VANES IN A GENTLY WAY. DAMAGE TO THE VANES CAN OCCUR IF YOU PUSH THEM HARD TO THE OUTER POSITIONS. (a) Fasten the Angle of Attack (AOA) calibration tools to the LH and the RH AOA transmitters: – (LH) TES–4054332–001 – (RH) TES–4054332–002. (b) Turn the LH AOA vane fully clockwise. (c) Turn the RH AOA vane fully counter–clockwise. (d) Make sure the flaps are at 0 

. (e) On the LH circuit breaker panel 11VU, close the circuit breaker:

LABEL POS C/B
STAB & WING AUT CTL K–21 1HP (f) On the overhead panel STAB & WING 18VU, set the switch AUTO CYCLING to OFF. (g) On the overhead panel ENGINE 42VU, set the L and R Engine Anti–Ice to OFF. (h) On the LH circuit breaker panel 9VU, open the circuit breaker:

LABEL POS C/B
STALL WARN CHAN 1 E–7 13WH (i) On the RH circuit breaker panel 10VU, open these circuit breakers:

LABEL POS C/B
STALL WARN CHAN 2 L–6 2WH STICK PUSHER L–4 36WH

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Page 7 of 24 (j) Supply the 28 VDC external power (Ref. AMM 12–00–00, servicing). (k) At 1VU, make sure that the indication light in the ICE SPEED push–button is OFF. (2) Do the test of the stall warning functions, flap 0  and non–icing condition: (a) On the CWP, make sure the amber caution–lights L STALL FAIL and R STALL FAIL are illuminated. (b) On the RH circuit breaker panel 10VU, close the circuit breaker:

LABEL POS C/B
STICK PUSHER L–4 36WH
(c) On the CWP, make sure the amber caution–lights L STALL FAIL and R STALL FAIL remains ON. (d) On the RH circuit breaker panel 10VU, open the circuit breaker:

LABEL POS C/B
STICK PUSHER L–4 36WH
(e) On the LH circuit breaker panel 9VU, close the circuit breaker:

LABEL POS C/B
STALL WARN CHAN 1 E–7 13WH
(f) On the CWP, make sure the L STALL FAIL amber caution–light goes off. (g) On the RH circuit breaker panel 10VU, close the circuit breakers:

LABEL POS C/B
STALL WARN CHAN 2 L–6 2WH
(h) On the CWP, make sure the R STALL FAIL amber caution–light goes off. (i) On the overhead panel ENGINE 42VU, set the L and R Engine Anti Ice to ON and then back to OFF. (j) At the LH and the RH main landing–gear, install the WOW operating tool (TDO 5–4650224) on the WOW switches 5GA and 6GA in flight position. (k) Make sure to let a minimum of 6 minutes pass after the aircraft was set to flight position, then make sure that the ICE SPEED on the instrument panel 1VU does not come on. (This is to test that the latching relays for ice activation are reset by weight on wheels) (l) Turn the LH AOA vane counter–clockwise until the stall warning is activated. Make sure these warnings and cautions operate: – the stick shaker on the LH and the RH control columns – the aural warning (continuous clacker). (m) Make sure the measured angle from the LH calibration tool is 12.5  ± 1 

. (n) Turn the LH AOA vane clockwise until the stall warning stops. (o) Turn the RH AOA vane clockwise until the stall warning is activated. Make sure these warnings and cautions operate: – the stick shaker on the RH and the LH control columns – the aural warning (continuous clacker).

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Page 8 of 24 (p) Make sure the measured angle from the RH calibration tool is 12.5 ± 1 . (q) Turn the RH AOA vane counter–clockwise until the stall warning stops. (3) Do the test of the stall identification functions, flap 0 and non–icing condition: (a) On the RH circuit breaker panel 10VU, close the circuit breaker:

LABEL POS C/B
STICK PUSHER L–4 36WH
(b) Make sure the PUSHER DISARM switch lights (31WH and 32WH) on the LH and RH side panels 5VU and 6VU do not come on. If the PUSHER DISARM switch lights (31WH and 32WH) come on, proceed as follows:

1 Set the spring–loaded STICK PUSHER RESET switch (27WH) on the RH electrical center 306VU to the ACTIVE position and release it. Make sure the PUSHER DISARM lights goes off. (c) Turn the RH AOA vane slowly clockwise until the PUSH 2 lights of the indicator lights (1WH and 6WH) on the LH and RH instrument panels 3VU and 4VU come on. Make sure the PUSHER SYSTEM amber caution–light on the CWP (3WW) comes on. (d) Make sure the measured angle from the RH calibration tool is 19 ± 1 . (e) Turn back the RH AOA vane slowly until the PUSH 2 lights goes off. (f) Pull the control column fully aft.
CAUTION : DO NOT OPERATE THE STALL WARNING PUSHER SYSTEM FOR MORE THAN A MAXIMUM OF 10 SECONDS CONTINUOUSLY. ALLOW THE SYSTEM A MINIMUM OF 1 MINUTE OF NON–OPERATION BEFORE YOU CONTINUE THE TEST. IF YOU RUN THE PUSHER SYSTEM FOR MORE THAN 10 SECONDS, THE PUSHER SERVO ACTUATORS CAN OVERHEAT. (g) Turn the LH AOA vane slowly counter–clockwise until the stick pusher is operated. Make sure the PUSH 1 and the PUSH 2 lights come on at the same time. (h) Make sure the measured angle from the LH calibration tool is 19 ± 1 . (i) Turn back the LH AOA vane to an angle between the stall warning and the stall identification, e.g. 16 . Make sure the PUSH 1 and the PUSH 2 lights are on. (j) Turn the RH AOA vane fully counter–clockwise. Make sure the stick pusher is deactivated and the PUSH 1 and the PUSH 2 lights goes off.
CAUTION : DO NOT OPERATE THE STALL WARNING PUSHER SYSTEM FOR MORE THAN A MAXIMUM OF 10 SECONDS CONTINUOUSLY. ALLOW THE SYSTEM A MINIMUM OF 1 MINUTE OF NON–OPERATION BEFORE YOU CONTINUE THE TEST. IF YOU RUN THE PUSHER SYSTEM FOR MORE THAN 10 SECONDS, THE PUSHER SERVO ACTUATORS CAN OVERHEAT. (k) Turn the RH AOA vane slowly clockwise until the PUSH 1 and the PUSH 2 lights come on and the pusher is operated. (l) Turn the RH AOA vane back to, e.g. 16 and make sure the PUSH 1 and the PUSH 2 lights are still on and the pusher is operated. (m) Turn the LH AOA vane fully clockwise and make sure the PUSH 1 and the PUSH 2 lights goes off and the pusher is deactivated. (n) Turn the RH AOA vane fully counter–clockwise.

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Page 9 of 24 (4) Do the test of the stall identification functions, flap 35 and non–icing condition: (a) Set the flap selector to 35 . (b) Make sure that the PUSHER DISARM switch lights (31WH and 32WH) on the left and the right side panels 5VU and 6VU not are on. If the PUSHER DISARM switch lights (31WH and 32WH) are on, proceed as follows:

1 Set the spring–loaded STICK PUSHER RESET switch (27WH) on the RH electrical center 306VU to the ACTIVATE position and release it. Make sure the PUSHER DISARM lights goes off. (c) Turn the RH AOA vane slowly clockwise until the PUSH 2 lights of the indicator lights (1WH and 6WH) on the left and right instrument panels 3VU and 4VU come on. Make sure the PUSHER SYSTEM amber caution–light on the CWP (3WW) comes on. (d) Make sure the measured angle from the RH calibration tool is 20 ° ± 1 °

. (e) Turn back the RH AOA vane slowly until the PUSH 2 lights goes off. (f) Pull the control column fully aft.
CAUTION : DO NOT OPERATE THE STALL WARNING PUSHER SYSTEM FOR MORE THAN A MAXIMUM OF 10 SECONDS CONTINUOUSLY. ALLOW THE SYSTEM A MINIMUM OF 1 MINUTE OF NON–OPERATION BEFORE YOU CONTINUE THE TEST. IF YOU RUN THE PUSHER SYSTEM FOR MORE THAN 10 SECONDS, THE PUSHER SERVO ACTUATORS CAN OVERHEAT. (g) Turn the LH AOA vane slowly counter–clockwise until the stick pusher is operated. Make sure the PUSH 1 and PUSH 2 lights come on at the same time. (h) Make sure the measured angle from the LH calibration tool is 20 ° ± 1 °

. (i) Turn back the LH AOA vane to an angle between the stall warning and the stall identification, e.g. 16 ° . Make sure the PUSH 1 and the PUSH 2 lights are on. (j) Turn the RH AOA vane fully counter–clockwise. Make sure the stick pusher is deactivated and the PUSH 1 and PUSH 2 lights goes off.
CAUTION : DO NOT OPERATE THE STALL WARNING PUSHER SYSTEM FOR MORE THAN A MAXIMUM OF 10 SECONDS CONTINUOUSLY. ALLOW THE SYSTEM A MINIMUM OF 1 MINUTE OF NON–OPERATION BEFORE YOU CONTINUE THE TEST. IF YOU RUN THE PUSHER SYSTEM FOR MORE THAN 10 SECONDS, THE PUSHER SERVO ACTUATORS CAN OVERHEAT. (k) Turn the RH AOA vane slowly clockwise until the PUSH 1 and the PUSH 2 lights come on and the pusher is operated. (l) Turn the RH AOA vane back to, e.g. 16 and make sure the PUSH 1 and the PUSH 2 lights are still on and the pusher is operated. (m) Turn the LH AOA vane fully clockwise and make sure the PUSH 1 and the PUSH 2 lights goes off and the pusher is deactivated. (n) Turn the RH AOA vane fully counter–clockwise. (5) Do the test of the stall warning functions, flap 0 and icing condition: (a) Set the flap selector to 0 . (b) Make sure that a minimum of 6 minutes has passed after weight off wheel and after power up. On the overhead panel ENGINE 42VU, set the Left Engine Anti Ice to ON. Make sure that the push button switch ICE SPEED on the instrument panel 1VU comes on (blue light).

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Page 10 of 24 (c) Momentarily press and release the push button switch ICE SPEED and make sure that the blue light NOT goes out.
NOTE : The blue light in the push button switch will go out during the time that the push button switch is pressed. (d) Turn the LH AOA vane counter–clockwise until the stall warning is activated. Make sure these warnings and cautions operate: – the stick shaker on the LH and the RH control columns – the aural warning (continuous clacker). (e) Make sure the measured angle from the LH calibration tool is 5.9  ± 1 

. (f) Turn the LH AOA vane clockwise until the stall warning stops. (g) Turn the RH AOA vane clockwise until the stall warning is activated. Make sure these warnings and cautions operate: – the stick shaker on the RH and the LH control columns – the aural warning (continuous clacker). (h) Make sure the measured angle from the RH calibration tool is 5.9  ± 1 

. (i) Turn the RH AOA vane counter–clockwise until the stall warning stops. (j) On the overhead panel ENGINE 42VU, set the Left Engine Anti Ice to OFF. Make sure that the blue indication light in the ICE SPEED push button, on the instrument panel 1VU, is still ON. (k) Press the push button switch ICE SPEED and make sure the indication light in the switch goes off. (6) Do the test of the stall identification functions, flap 0  and icing condition: (a) Make sure that a minimum of 6 minutes has passed after weight off wheel and after power up. On the overhead panel ENGINE 42VU, set the Left Engine Anti Ice to ON. Make sure that the push button switch ICE SPEED on the instrument panel 1VU comes on (blue light). (b) Turn the RH AOA vane slowly clockwise until the PUSH 2 lights of the indicator lights (1WH and 6WH) on the LH and RH instrument panels 3VU and 4VU come on. Make sure the PUSHER SYSTEM amber caution–light on CWP (3WW) comes on. (c) Make sure the measured angle from the RH calibration tool is 19  ± 1 

. (d) Turn back the RH AOA vane slowly until the PUSH 2 lights goes off. (e) Pull the control column fully aft.
CAUTION : DO NOT OPERATE THE STALL WARNING PUSHER SYSTEM FOR MORE THAN A MAXIMUM OF 10 SECONDS CONTINUOUSLY. ALLOW THE SYSTEM A MINIMUM OF 1 MINUTE OF NON–OPERATION BEFORE YOU CONTINUE THE TEST. IF YOU RUN THE PUSHER SYSTEM FOR MORE THAN 10 SECONDS, THE PUSHER SERVO ACTUATORS CAN OVERHEAT. (f) Turn the LH AOA vane slowly counter–clockwise until the stick pusher is operated. Make sure the PUSH 1 and the PUSH 2 lights come on at the same time. (g) Make sure the measured angle from the LH calibration tool is 19  ± 1 

. (h) Turn back the LH AOA vane to an angle between the stall warning and the stall identification, e.g. 12  . Make sure the PUSH 1 and the PUSH 2 lights are on. (i) Turn the RH AOA vane fully counter–clockwise. Make sure the stick pusher is deactivated and the PUSH 1 and the PUSH 2 lights goes off.

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Page 11 of 24 CAUTION : DO NOT OPERATE THE STALL WARNING PUSHER SYSTEM FOR MORE THAN A MAXIMUM OF 10 SECONDS CONTINUOUSLY. ALLOW THE SYSTEM A MINIMUM OF 1 MINUTE OF NON–OPERATION BEFORE YOU CONTINUE THE TEST. IF YOU RUN THE PUSHER SYSTEM FOR MORE THAN 10 SECONDS, THE PUSHER SERVO ACTUATORS CAN OVERHEAT. (j) Turn the RH AOA vane slowly clockwise until the PUSH 1 and the PUSH 2 lights come on and the pusher is operated. (k) Turn the RH AOA vane back to, e.g. 12 and make sure the PUSH 1 and the PUSH 2 lights are still on and the pusher is operated. (l) Turn the LH AOA vane fully clockwise and make sure the PUSH 1 and the PUSH 2 lights goes off and the pusher is deactivated. (m) Turn the RH AOA vane fully counter–clockwise. (n) On the overhead panel ENGINE 42VU, set the Left Engine Anti Ice to OFF. Make sure that the blue indication light in the ICE SPEED push button, on the instrument panel 1VU is still ON. (o) Press the push button switch ICE SPEED and make sure the indication light in the switch goes off. (7) Do the test of the stall warning functions, flap 35 and icing condition: (a) Set the flap selector to 35 . (b) Make sure that a minimum of 6 minutes has passed after weight off wheel and after power up. On the overhead panel ENGINE 42VU, set the Right Engine Anti Ice to ON. Make sure that the push button switch ICE SPEED on the instrument panel 1VU comes on (blue light). (c) Turn the LH AOA vane counter–clockwise until the stall warning is activated. Make sure these warnings and cautions operate: – the stick shaker on the LH and the RH control columns – the aural warning (continuous clacker). (d) Make sure the measured angle from the LH calibration tool is 5.7 ± 1 . (e) Turn the LH AOA vane clockwise until the stall warning stops. (f) Turn the RH AOA vane clockwise until the stall warning is activated. Make sure these warnings and cautions operate: – the stick shaker on the RH and the LH control columns – the aural warning (continuous clacker). (g) Make sure the measured angle from the RH calibration tool is 5.7 ± 1 . (h) Turn the RH AOA vane counter–clockwise until the stall warning system stops. (i) On the overhead panel ENGINE 42VU, set the Right Engine Anti Ice to OFF. Make sure that the blue indication light in the ICE SPEED push button, on the instrument panel 1VU is still ON. (j) Press the push button switch ICE SPEED and make sure the indication light in the switch goes off. (8) Do the test of the stall identification functions, flap 35 and icing condition: (a) Make sure that a minimum of 6 minutes has passed after weight off wheel and after power up. On the overhead panel ENGINE 42VU, set the Right Engine Anti Ice to ON. Make sure that the push button switch ICE SPEED on the instrument panel 1VU comes on (blue light).

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Page 12 of 24 (b) Turn the RH AOA vane slowly clockwise until the PUSH 2 lights of the indicator lights (1WH and 6WH) on the left and right instrument panels 3VU and 4VU comes on. Make sure the PUSHER SYSTEM amber caution–light on CWP (3WW) comes on. (c) Make sure the measured angle from the RH calibration tool is 20 ° ± 1 °

. (d) Turn back the RH AOA vane slowly until the PUSH 2 lights goes off. (e) Pull the control column fully aft.
CAUTION : DO NOT OPERATE THE STALL WARNING PUSHER SYSTEM FOR MORE THAN A MAXIMUM OF 10 SECONDS CONTINUOUSLY. ALLOW THE SYSTEM A MINIMUM OF 1 MINUTE OF NON–OPERATION BEFORE YOU CONTINUE THE TEST. IF YOU RUN THE PUSHER SYSTEM FOR MORE THAN 10 SECONDS, THE PUSHER SERVO ACTUATORS CAN OVERHEAT. (f) Turn the LH AOA vane slowly counter–clockwise until the stick pusher is operated. Make sure the PUSH 1 and PUSH 2 lights comes on at the same time. (g) Make sure the measured angle from the LH calibration tool is 20 ° ± 1 °

. (h) Turn back the LH AOA vanes to an angle between the stall warning and the stall identification, e.g. 12 ° . Make sure the PUSH 1 and the PUSH 2 lights are on. (i) Turn the RH AOA vane fully counter–clockwise. Make sure the stick pusher is deactivated and the PUSH 1 and PUSH 2 lights goes off.
CAUTION : DO NOT OPERATE THE STALL WARNING PUSHER SYSTEM FOR MORE THAN A MAXIMUM OF 10 SECONDS CONTINUOUSLY. ALLOW THE SYSTEM A MINIMUM OF 1 MINUTE OF NON–OPERATION BEFORE YOU CONTINUE THE TEST. IF YOU RUN THE PUSHER SYSTEM FOR MORE THAN 10 SECONDS, THE PUSHER SERVO ACTUATORS CAN OVERHEAT. (j) Turn the RH AOA vane slowly clockwise until the PUSH 1 and the PUSH 2 lights comes on and the pusher is operated. (k) Turn the RH AOA vane back to, e.g. 12 and make sure the PUSH 1 and the PUSH 2 lights are still on and the pusher is operated. (l) Turn the LH AOA vane fully clockwise and make sure the PUSH 1 and the PUSH 2 lights goes off and the pusher is deactivated. (m) Turn the RH AOA vane fully counter–clockwise. (n) On the overhead panel ENGINE 42VU, set the Right Engine Anti Ice to OFF. Make sure that the blue indication light in the ICE SPEED push button, on the instrument panel 1VU is still ON. (o) Press the push button switch ICE SPEED and make sure the indication light in the switch goes off.

(9) Do the test of the test functions: (a) Remove the WOW operating tool from the LH and the RH WOW switches 5GA and 6GA. (to make the aircraft in ground configuration). (b) Set and hold the STALL 1 switch on the TEST 1 panel (19VU) to the up position for at least 6 seconds: – make sure that the aural warning starts and the two stick shakers start to operate – make sure that the PUSH 1 lights and the PUSHER SYSTEM caution light come on.

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Page 13 of 24 (c) Set and hold the STALL 2 switch on the TEST 1 panel (19VU) to the up position for at least 6 seconds: – make sure that the aural warning starts and the two stick shakers start to operate – make sure that the PUSH 2 lights and the PUSHER SYSTEM caution light come on. (d) Pull the control column aft and, at the same time, set the STALL 1 and the STALL 2 switches on the TEST 1 panel to the up position: – make sure that the aural warning starts and the two stick shakers start to operate – make sure that the PUSH 1 and PUSH 2 lights come on – make sure that the pusher starts to operate the control columns forward. NOTE : PUSHER SYSTEM caution light may come on during this test depending on the pusher actuator. This does not indicate a failure. (e) Pull the control column aft and, at the same time, set the STALL 1 and the STALL 2 switches on the TEST 1 panel to their lower position. – make sure that the aural warning starts and the two stick shakers start to operate (In this mode, the servo–actuator internal G–switch is tested, the operation of the stick pusher is not started.)
NOTE : PUSHER SYSTEM caution light may come on during this test depending on the pusher actuator. This does not indicate a failure. (10) Do the test of the deactivating function: (a) Push the PUSHER DISARM switch light (31WH) on the left side panel 5VU. Make sure the LH and the RH PUSHER DISARM switch lights (31WH and 32WH) on the left and the right side panels 5VU and 6VU come on. (b) Set the STALL 1 and the STALL 2 switches (29WH and 30WH) on the TEST 1 panel 19VU to the up position. Make sure there is no PUSH 1 or PUSH 2 indication on the left and the right instrument panels 3VU and 4VU. (c) Set the spring–loaded STICK PUSHER RESET switch (27WH) on the RH electrical center 306VU to the ACTIVATE position and release it. Make sure the PUSHER DISARM lights goes off. (d) Push the PUSHER DISARM switch light (32WH) on the right side panel 6VU. Make sure the LH and the RH PUSHER DISARM switch lights (31WH and 32WH) on the left and the right side panels 5VU and 6VU come on. (e) Set the spring–loaded STICK PUSHER RESET switch (27WH) on the RH electrical center 306VU to the ACTIVATE position and release it. Make sure the PUSHER DISARM lights goes off. (11) Do the test of the ICE SPEED push–button lamp: (a) On the TEST 1 panel 19VU, set the lamp test switch to the LWR position and make sure that the blue indication light in the ICE SPEED push–button comes on. (b) When the ICE SPEED push–button lamp is on: – set the DIM/BRT switch on the INT LIGHT panel 30VU to DIM and make sure that the button light is dimmed – set the DIM/BRT switch on the INT LIGHT panel 30VU to BRT and make sure that the button light goes to bright.

F. JOB CLOSE–UP (1) Remove the electrical power (Ref. AMM 12–00–00). (2) Remove the AOA calibration tools from the LH and the RH AOA transmitters.

# Service Bulletin

11 July 2014 

# 340–27–121

Page 14 of 24 (3) Close the access: (a) Remove all the tools and equipment from the work area. Make sure the work area is clean.
FOR A/C 004–078 (b) At the avionics rack, install the access panel 210AZ (Ref. AMM 06–30–00).
FOR A/C 079–459 (c) At the avionics rack, install the access panel 220AZ (Ref. AMM 06–30–00).
FOR A/C ALL

3. MATERIAL INFORMATION

A. Modification Kit No SAAB 340–27–121–01 contains:

Item Part Number Qty Nomenclature Designation Remarks10 0020AK6–1 2 Stall warning computer 3WH, 4WH –

12 7292183–007 1 Label ICE SPD CANCEL At 1VU, (3WHC)

13 7292183–005 1 Label SW ICE IND At 12VU S–28, (2WHC)

B. Local supply

Item Part Number Qty Nomenclature Designation Remarks – – AR Lacing cord – –

C. Removal
FOR A/C PRE SB 340–27–098 and POST SB340–27–120

Item Part Number Qty Nomenclature Designation Remarks

R110 20AK O/T 0020AK 2 Stall warning computer 3WH, 4WH –

or
R110 20AK1 O/T 0020AK1 2 Stall warning computer 3WH, 4WH –

or R110 20AK2 MOD A O/T 0020AK2 MOD A 2 Stall warning computer 3WH, 4WH –

or
R110 20AK4 O/T 0020AK4 2 Stall warning computer 3WH, 4WH –

# Service Bulletin

11 July 2014 

# 340–27–121

Page 15 of 24 FOR A/C POST SB 340–27–098 and POST SB340–27–120

Item Part Number Qty Nomenclature Designation Remarks

R110 20AK6 O/T 0020AK6 2 Stall warning computer 3WH, 4WH (For A/C POST SB340–27–098)

FOR A/C POST SB340–27–109

Item Part Number Qty Nomenclature Designation Remarks

R110 20AK4 O/T 0020AK4 2 Stall warning computer 3WH, 4WH –

FOR A/C PRE SB340–27–109, or FOR A/C PRE SB340–27–116 and POST SB340–27–120

Item Part Number Qty Nomenclature Designation Remarks R112 7292183–009 1 Blank label – At 1VU, (3WHC) R115 716306 1 C/B Cover – At 12VU S–28, (2WHC)

FOR A/C ALL

# Service Bulletin

11 July 2014 

# 340–27–121

Page 16 of 24 R110 R110

R110 R110

A31684 

# Stall Warning Computers – Removal and Installation FIG. 1

# Service Bulletin

11 July 2014 

# 340–27–121

Page 17 of 24 

# B RHS C/B PANEL 12VU 13

R115

COVER 

# C RHS C/B PANEL 10VU 

# A

C

B

POST MOD 

# A 12

PRE MOD 

# A R112

A31685 

# Flight Compartment – Activation of Parked System for A/C PRE SB340–27–109, or for A/C PRE SB340–27–116 and POST SB340–27–120 FIG. 2

# Service Bulletin

11 July 2014 

# 340–27–121

Page 18 of 24 A31687 

# B RHS C/B PANEL 12VU 13

IF APPLICABLE REMOVE INOP LABEL 

# C RHS C/B PANEL 10VU 

# A

C

B

POST MOD 

# A 12

PRE MOD 

# A REMOVE INOP LABEL



# Flight Compartment – Activation of Parked System for A/C POST SB340–27–109, or for A/C POST SB340–27–116 and POST SB340–27–120 FIG. 3

# Service Bulletin

11 July 2014 

# 340–27–121

Page 19 of 24 A31688 

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# Service Bulletin

11 July 2014 

# 340–27–121

Page 20 of 24 A31689 

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# Service Bulletin

Date Month Year

Revison X, Date Month Year 

# 340–XX–XXX

Page 22Service Bulletin11 July 2014340–27–121Page 23/24 of 24A31691

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# Service Bulletin

Date Month Year

Revison X, Date Month Year 

# 340–XX–XXX

Page 24