The primary purpose of the Stall Protection System (SPS) is to prevent the aircraft from entering a potentially hazardous stall situation. The SPS provides the flight crew with warnings at the onset of a stall. It will also cause the control columns to move forward to pitch down if the near stall condition (impending stall condition) is not corrected. A Mach transducer and source select panel are also installed on aircraft S/N 9001-9158. The Mach transducer and source select panel are removed with the installation of the Integrated Electronic Standby Instrument (IESI) on aircraft S/N 9159 and subs.

It also makes sure that the aircraft does not go into an angle-of-attack (AOA) area where dangerous wing drop or a deep stall can occur. For fail-safe operation, the system has two subsystems that are the same. If the aircraft goes near the stall condition, the stick shaker will start to shake. The vibration will continue until the aircraft angle-of-attack is decreased.

The SPS alerts the flight crew of an impending stall via a stick shaker, STALL indication on the Primary Flight Display (PFD) and the aural warning. An autopilot disconnect and auto ignition is also commanded. In the event the flight crew does not recover the aircraft prior to entering the stall condition, the SPS activates a column pusher, which maneuvers the aircraft to a reduced angle of attack to avert the stall.

The SPS uses the parameters that follow to calculate stall warnings and stall protection:

• Angle of attack (AOA)
• Mach (Applicable only for Global Express, or on A/C 9127 to 9157 for Global 5000)
• Integrated electronic standby instrument (IESI) (Applicable only for Global XRS, or on A/C 9158 and Subs for Global 5000)
• Flap/slat position
• SPS mode (ADVANCE or NORM mode)

There are different AOA firing angles at which different SPS operations will occur and they are as follows:

• Auto-ignition firing angle: To prevent engine flame-out when a specified high AOA occurs, the SPS will start continuous ignition to the engines when the auto-ignition firing angle is sensed
  
  
• Shaker firing angle: If the AOA increases more, the SPS will supply a voice STALL warning, and will cause the stick shakers to shake the control columns when the shaker firing angle is sensed. If the autopilot is engaged, it will be disengaged at the same time as the stick shaker starts the vibrations. The STALL voice continues as long as the stick shaker operates
  
  
• Pusher firing angle: If the AOA continues to increase, the SPS stick pusher will move the control columns forward to pitch the aircraft nose down, when the pusher firing angle is sensed by the two SPC channels. A red STALL warning annunciation will also show in the ADI sphere on the primary flight displays (PFDs) when a SPC channel sends a push command. The pitch disconnect lock will also be energized to make sure the elevator torque tubes stay connected when the stick pusher operates. You can cancel the pusher and pitch disconnect lock functions if one of the PUSHER switches on the STALL control panels is set to OFF

The stall protection system has the components that follow:

• Dual channel stall protection computer
• Stick shakers
• Angle-of-attack sensors
• Integrated electronic standby instrument (Applicable only for Global XRS, or on A/C 9158 and Subs for Global 5000)
• Mach transducer (Applicable only for Global Express, or on A/C 9127 to 9157 for Global 5000)
• Stick pusher actuator
• Stick pusher capstan
• STALL control panels
• MACH TRANSDUCER Control Panel (Applicable only for Global Express, or on A/C 9127 to 9157 for Global 5000)

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On Global Express, or on A/C 9127 to 9157 for Global 5000:

The stall protection computer (SPC) is digital and has two identical channels, channel A and channel B. These two channels work independently. Angle-of-attack (AOA) sensor vane, flap and slat position, lateral acceleration, and weight-on-wheels (WOW) inputs are isolated from each other. These inputs are supplied to each channel of the stall protection computer. The SPC processes input signals from the AOA sensors, Mach transducer and other aircraft systems and supplies outputs to operate the stick shakers, stick pusher and aural/visual stall warnings.

On Global XRS, or on On A/C 9158 and Subs for Global 5000:

The stall protection computer (SPC) is digital and has two identical channels, channel A and channel B. These two channels work independently. Angle-of-attack (AOA) sensor vane, flap and slat position, lateral acceleration, and weight-on-wheels (WOW) inputs are isolated from each other. These inputs are supplied to each channel of the stall protection computer. The SPC processes input signals from the AOA sensors and other aircraft systems and supplies outputs to operate the stick shakers, stick pusher and aural/visual stall warnings.

The stall protection computer uses lateral acceleration inputs from the 3-axis accelerometer of the flight data recorder system to make corrections to the angle-of-attack sensor inputs. These corrections to the angle-of-attack sensor inputs adjust for the effects of movements such as sideslips.

The stall protection computer monitors the angle-of-attack sensor inputs and rejects those inputs that are caused by the effects of gusts at low aircraft speeds. The stall protection computer also rejects those angle-of-attack sensor inputs that are caused by flutter at high aircraft speeds.

The stick pusher will not operate unless the two channels of the stall protection computer send the push signal to the pusher at the same time. The stall protection computer is installed in the forward avionics compartment at FS265.00+32.00 for Global 5000 and at FS265.00 for Global Express/XRS right hand side.

When the aircraft is weight-on-wheels (WOW), the stall protection computer will not operate. But, the stall protection computer will operate for the self-test circuit, indications and the autopilot disconnect.

The SPC has extensive built-in test (BIT) and diagnostic functions. BIT has 3 modes of operations:

• Power-up BIT
• Continuous BIT
• Pilot activated test (PAT)

On Global Express, or on A/C 9127 to 9157 for Global 5000, fault data from BIT is supplied through ARINC 429 bus to EICAS and CAIMS. Fault data is also kept in non-volatile memory (NVM) in the SPC. The EICAS (CAS) messages supplied by the SPC are as follows:

• STALL PROTECT FAIL (caution)
• SHAKER 1-2 FAIL (advisory)
• MACH TRANSDUCER FAIL (advisory)
• PITCH DISC FAULT (advisory)
• STALL WARN ADVANCE (advisory)

On Global XRS, or on A/C 9158 and Subs for Global 5000, the EICAS (CAS) messges supplied by the SPC are as follows:

• STALL PROTECT FAIL (caution)
• IESI FAIL (advisory)
• SHAKER 1-2 FAIL (advisory)
• PITCH DISC FAULT (advisory)
• STALL WARN ADVANCE (advisory)

For information on the STALL PROTECT FAIL Nuicance CAS Message issue, refer to "STALL PROTECT FAIL" Nuisance CAS Message Advisory Wire (AW700-27-0275).

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The STALL control panels are each installed on the pilot and copilot side panels in the flight compartment. On each STALL control panel, there is a PUSHER ON/OFF toggle-switch which controls the power to the stick pusher actuator. The two switches are connected in series and must be set to ON at the same time for the stick pusher to function. When the two PUSHER toggle-switches are set to the ON position, the 28 VDC battery bus supplies power to the stick pusher and the elevator disconnect (lock) solenoid. To stop the stick pusher function, set one of the PUSHER switches to OFF.

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For Global Express, or on A/C 9002-9157 for Global 5000:

The mach transducer provides the Stall Protection Computer (SPC) with dissimilar source for Mach number, airspeed and altitude inputs to cross check for common mode software errors from the Micro Air Data Computer (MADC). However, MADC is always the primary source of air data. The Mach transducer measures the physical parameters of indicated static pressure (Psi) and total pressure (Pt). It is installed in the forward area of the copilot´s side panel assembly. A pitot-static system supplies pitot-static pressures to the Mach transducer.

Static Source Error Correction (SSEC) is applied on Psi based on flap position, slat position, fuselage angle of attack (AOA) and indicated Mach (Mi). Air data parameters are transmitted over a dual output low speed digital ARINC 429 bus. The air data parameters supplied include corrected static pressure (Ps), total pressure (Pt), computed airspeed (VC), computed Mach (Mc) and pressure altitude (H). Pressure altitude is calculated with 1962 U.S. Standard Atmosphere. Computed airspeed and Mach number are calculated with NASA TN D-822.

The Mach transducer uses built-in-test (BIT) to give LRU level fault indication and isolation (CAS/CAIMS messages).

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On Global Express, or on A/C 9127 to 9158 for Global 5000:

The MACH TRANSDUCER control panel is installed in the copilot side console panel.

The Mach transducer connects to the standby pitot-static probe and the static port of pitot-static probe 1 through two PITOT/STATIC SELECT valves in the control panel. Each valve has two positions: PITOT/STATIC and CLOSED. If the Mach transducer fails, the valves can be used to isolate the Mach transducer from the rest of the pitot-static system. To do this, the select valves are set to the CLOSED position. The levers of the select valves are barred together.

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For Global XRS, or on A/C 9158 and Subs for Global 5000:

The IESI replaces the Mach transducer for the alternate source of Mach number, airspeed and altitude inputs to cross check for common mode software errors from the Micro Air Data Computer (MADC). MADC is always the primary source of air data.

The IESI is an independent source of altitude, airspeed and barometric pressure. It measures the physical parameters of indicated static pressure (Psi) and total pressure (Pt). It is installed in the main instrument panel in the flight compartment. A pitot-static system supplies pitot-static pressures to the IESI.

Static Source Error Correction (SSEC) is applied on Psi based on flap position, slat position, fuselage angle of attack (AOA) and indicated Mach (Mi). Air data parameters are transmitted over a dual output low speed digital ARINC 429 bus. The air data parameters supplied include corrected static pressure (Ps), total pressure (Pt), computed airspeed (Vc), computed Mach (Mc) and pressure altitude (H). Pressure altitude is calculated with 1962 U.S. Standard Atmosphere. Computed airspeed and Mach number are calculated with NASA TN D-822.

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One stick shaker is installed on the forward side of each control column. The stick shakers shake the control columns to tell the pilot and copilot of a near stall condition. Each channel of the stall protection computer controls and operates its related stick shaker.

The stick shaker actuator is a mechanical vibrator. It has a high speed motor that turns a weight through a 10:1 gear ratio. The weight movement gives the centrifugal force that shakes the control column. This simulates aircraft buffeting before a stall condition.

The stick shaker provides tactile indication of stall warning. When activated, a 28 VDC motor drives an off-center counterweight attached to the control column, resulting in shaking motion. The shaking motion is strong enough that even with one shaker failed, the shake can be felt on both control columns via the control column torque tube. The pilot stick shaker is controlled by the SPC A channel, and the copilot stick shaker by the SPC B channel.

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The function of the stick pusher is to push the control column forward to prevent a stall condition. The stick pusher includes the components that follow:

• Stick pusher actuator
• Stick pusher capstan

The pusher actuator is a rotary output electromechanical device designed to accept two “push” input signals which cause counterclockwise motion of the output pinion. The main features of the actuator are: An electronic circuit, a permanent magnet DC motor, an electromechanical disconnect clutch and associated mechanical gearing. The pusher force against the control column is 80 lb.

The capstan is a mechanical assembly designed to accept a rotary output from an actuator gear pinion and provide a means of driving aircraft control cables through the use of a cable pulley. The capstan assembly also contains an override slip clutch that allows the cable pulley to be rotated in the event that the actuator output is seized.

The stick pusher capstan is a pulley which transmits the movement of the output gear pinion of the actuator to the forward elevator quadrant by a cable. The capstan is attached to the bottom of the stick pusher actuator.

The actuator returns active and fail signals to the SPC for BIT test and inadvertent, inactive and push detection.

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The angle-of-attack (AOA) sensor is a swept vane type, heated dual resolver sensor. It is attached externally on each side of the forward fuselage. The sensor vane turns to align with the airflow to measure the direction of the airflow relative to the fuselage at FS198.10+32.00 for Global 5000 and at FS198.10 for Global Express/XRS. The vane movement is changed through a 1:1 gear ratio with resolvers to supply electrical outputs which are proportional to the aircraft AOA. The vane has self-regulating 115 VAC anti-icing heaters. It also has a viscous damper to keep the vane travel to the minimum in turbulence.

The AOA vane measures the aircraft angle of attack, from -45 to +45 degrees. The signals from the left and right AOA sensors are transmitted to the related left and right channels of the stall protection computer.

Wiring strapping for left AOA sensor is done at TM41, and that for right AOA sensor is done at TM40. These strappings must not be changed. They are used to electrically compensate mechanical offset induced during the drilling process in production.

A STALL TEST is available from the TEST page on the EMS CDU. This is also known as the pilot activated test (PAT). During PAT, the AOA output is increased to simulate the near stall condition. The stick shaker, stick pusher and pitch disconnect lock are energized in the PAT. PAT can only be done when the aircraft is in WOW for more than 15 seconds, and the computed airspeed is less than 70 knots.

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The three-axis AC accelerometer provides lateral acceleration to the SPC. The other two axes are used by the Flight Data Recorder. Lateral acceleration information is used by the SPC to compensate for different left or right AOA vane angles during a sideslip. The accelerometer is installed in the left main landing gear wheel well at FS723.

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The master disconnect momentary switches on the control columns are used to disconnect the pusher, if required. When either pilot or copilot disconnect button is pressed, the SPC will discontinue a push while button is held. If the button is held for more than a second, CAS caution message STALL PROTECT FAIL will be displayed.

For Global Express Pre SB 700-27-025, the master disconnect switches on the control wheels supply discrete ground signals and can be used to cancel the stick pusher function orpilot activated test (PAT) quickly.

Note:
This pusher disconnect feature using the Master Disconnect Switches is removed on all JAA-certified airplanes by service bulletin SB 700-27-025. On these aircraft the stall pusher function is disabled by moving one of the Stick Pusher ON/OFF switches to the OFF position on the STALL control panel.

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The stall pusher ON/OFF switches on the side panels are used to disable or enable the SPC push command. The stall pusher ON/OFF switches are located on both pilot’s and copilot’s side panels and they are used for long term disabling of the pusher only. When either switch is in OFF, the SPC cannot command a push and the CAS caution message STALL PROTECTION FAIL will be displayed.

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The SPS operates in two modes: normal (NORM) mode and reversion/advance (REV) mode. The normal mode is the usual mode. The reversion mode is the alternative mode in which the shaker firing angles are advanced or set to lower angles. The selection of reversion mode can be manually made from the CNTL page on the EMS CDU, or automatically by annunciated failure of slats or wing anti-icing. The CNTL page on the EMS CDU shows the SPS mode that is in operation by the message of STALL WARN ADVANCE NORM or REV. The reversion mode is also annunciated by the EICAS advisory message STALL WARN ADVANCE. The reversion mode can only be changed back to normal mode through the EMS CDU when there is no annunciated slat or wing anti-icing failure.

Stick Pusher Operation

The stick pusher moves the control column forward causing pitch downwards and reduced Angle-of-Attack (AOA).

Activation

Stick pusher activates when the pusher compensated activation AOA exceeds the pusher firing angle. Must be true for both command and monitor functions from both SPC channels.

Deactivation

Stick pusher deactivates when the pusher compensated activation AOA is less than the pusher firing angle. The command or monitor functions from either SPC channel may deactivate pusher. Stall pusher switches set to OFF disable the stick pusher.

Inhibit

Stick pusher function is inhibited when any of the following are true:

• Both main gear wow inputs indicate aircraft on ground
• Compensated Air Speed is less than 70 knots
• Stall pusher switches are selected off

Stick Shaker Operation

The stick shaker vibrates control column to indicate to flight crew that the initial stall warning AOA has been reached.

Activation

Stick shaker activates when the shaker compensated AOA exceeds the shaker-firing angle. Only the SPC command functions control shaker activation.

The SPC command function from each channel independently controls one shaker. Channel A controls the pilot's shaker, and Channel B controls the copilot´s shaker.

Deactivation

Stick shaker deactivation occurs when the shaker compensated AOA is below the shaker-firing angle. The SPC command or monitor function from either SPC channel may deactivate shaker.

Inhibit

Stick shaker is inhibited when both main gear WOW inputs indicate that the aircraft is on ground, or when compensated airspeed is less than 70 knots.

Autopilot Disconnect

The autopilot disconnect disconnects the autopilot at first warning of stall condition to the autopilot (IAC) via the ARINC 429 bus.

Activation

The autopilot disconnect activates when the shaker compensated AOA exceeds the shaker-firing angle.

Deactivation

Deactivation occurs when the shaker compensated AOA is below the shaker-firing angle.

Inhibit

Inhibited when both main gear WOW inputs indicate aircraft on ground.

Auto-Ignition

Initiates engine ignition at first warning of stall condition.

Activation

Auto-ignition activated when the shaker compensated AOA exceeds the shaker-firing angle.

Deactivation

Auto-ignition deactivation occurs when the shaker compensated AOA is below the shaker-firing angle.

Inhibit

Auto-ignition inhibited when both main gear WOW inputs indicate aircraft on ground.

Pitch Disconnect Lock

Because of the high force exerted by the pusher motor, it is possible that the disconnect mechanism could activate if the pilot on the right side attempts to pitch up the aircraft during the pusher operation. This function engages a solenoid which prevents an elevator disconnect during pusher operation.

Activation

1.5 degrees before the pusher activates.

Deactivation

When pusher demand is canceled.

Inhibit

Inhibited when both main gear wow inputs indicate aircraft on ground or compensated airspeed is less than 70 knots.

Aural Warning

When a stall situation occurs, the SPC generates an ARINC 429 discrete output via DAU to IAC to activate the aural warning function. A pulsing horn and "STALL" voice will be activated together with the stick shaker.

Visual Warning

When stall situation occurs, the SPC generates an ARINC 429 discrete output via DAU to IAC to activate the central display function. A red STALL in a red box will be displayed on the attitude sphere of the PFD and the stick shaker will also be activated.

Low speed awareness (LSA) and low speed cue output transmitted via ARINC 429 bus are also displayed on PFD speed tape. A red LSA thermometer is displayed from the bottom of the airspeed tape to the position of tape that corresponds to calculated stall warning speed. A green line on the speed tape refers to the reference speed or minimum selectable speed.

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The SPC has extensive BIT and diagnostic capabilities. The SPC decodes the fault data and can isolate the faulty LRU. Test results are reported to the monitor lane and are logged in the NVM (which can be addressed during maintenance mode through CAIMS).

Power-up BIT

Upon application of power, the system checks the validity of the power supply, micro controller, RAM and ROM.

Continuous BIT

Various continuous functional tests are ensuring that the SPS components and the SPC interfaces are running correctly. These tests consist of checks for open or short inputs, cross channel data comparisons, ARINC to discrete data comparisons and functional checks on the SPC interfaces. The failures resulting from monitoring are displayed as CAS messages.

Jammed Vane Test

After attaining a CAS greater than 70 knots, the raw AOA value is tested for an out-of-range condition (±20 degrees). If the AOA value is out-of-range, the stall warning functions for the affected SPC channel are inhibited for 10 seconds after takeoff. Within 10 seconds after takeoff, an AOA cross-compare test will verify the AOA sensors agree within 5 degrees or fail the AOA sensor that was out of range on the takeoff roll.

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Initiated Built-In Test – EMS CDU

The pilot-activated stall test is initiated through EMS CDU. The test lasts about 15 seconds and checks each shaker individually, checks pusher for activation only under correct conditions, checks audio and visual warnings.

PAT also activates pitch disconnect lock and looks for proper feedback, simulates a stall event and verifies all proper operation, and pushes both columns forward at end of the test to allow the pilots to press the quick-disconnect buttons in order to verify their operation.

Note:
Master disconnect button deactivation of stick pusher operation only applies to non-JAA registered aircraft per SB 700-27-025.

Stall Test Sequence

Test 1	Internal BIT (subset of power-up BIT)
Test 2	Shaker commanded by channel A for 1 second (shaker No. 1 on). Pusher commanded by channel A, not by channel B, (no pusher)
Test 3	Shaker commanded by channel B for 1 sec (shaker No.2 on). Pusher commanded by channel B, not by channel A (no pusher)
Sweep Test	AOA −20 to +30 degrees, AOA rate 10 degrees per second. Shaker/aural alert at 10 degrees (shaker no.1/2 on). Pusher/visual alert at 20 degrees (pusher on)
Disconnect Test	Non-JAA registered aircraft: Pilots to test both disconnect switches (pusher releases). JAA registered aircraft: Pilots set PUSHER switch to OFF on the STALL PUSHER control panel (pusher releases).

CAIMS

The SPC will gather and store flight fault data when equipment failures occur during normal operation. Indicate system health by providing system status information and also run initiated bite tests. The system flight fault summary shall be accessed in the CAIMS maintenance mode. The SPC will also respond to Pilot Event Markers by storing "snapshot" data in NVM.

Initiated Built-In Test – CAIMS

The stall protection system provides assistance to maintenance personnel by identifying equipment with faults and performing IBIT. When CAIMS is active, system information is available through the CAIMS system diagnostics menus.

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
A40	STALL PROTECTION COMPUTER	ZONE(S) 132	27-32-01 [ GX ] [ GXRS ] [ G5000 ]
A203/A204	STICK SHAKERS	ZONE(S) 221/222	27-32-05 [ GX ] [ GXRS ] [ G5000 ]
MT136/MT137	ANGLE-OF-ATTACK SENSORS	ZONE(S) 221/222	27-32-09 [ GX ] [ GXRS ] [ G5000 ]
MT80	MACH TRANSDUCER	ZONE(S) 222	27-32-13 [ GX ] [ GXRS ] [ G5000 ]
A190	STICK PUSHER ACTUATOR	ZONE(S) 131	27-32-17 [ GX ] [ GXRS ] [ G5000 ]
-	STICK PUSHER CAPSTAN	ZONE(S) 131	27-32-21 [ GX ] [ GXRS ] [ G5000 ]
-	STALL CONTROL PANELS	ZONE(S) 220	27-32-33 [ GX ] [ GXRS ] [ G5000 ]
AP29	MACH TRANSDUCER CONTROL PANEL	ZONE(S) 222	27-32-37 [ GX ] [ GXRS ] [ G5000 ]
M14	INTEGRATED ELECTRONIC STANDBY INSTRUMENT	ZONE(S) 220	34-12-03 [ GX ] [ GXRS ] [ G5000 ]

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