Note: 
The Lightining Sensor System is available via SB 700-34-003 or SB 700-34-030 for Global Express, or via SB 700-34-030 for Global XRS, or on Global 5000. 

The lightning sensor system (LSS) identifies the location and the intensity of the lightning strikes during thunderstorms. It operates directly with the weather radar (WXR) system.

The LSS is a remote-controlled lightning (LX) detection system. It calculates the bearing, distance, and intensity of the lightning strikes around the aircraft. It collects the lightning data in an area of 120 or 360 degrees in a radius of 5 to 100 nmi. At a distance of 100 nmi, the lightning data is accurate to ±10% for the range and ±5 degrees for the bearing. The multi-function display (MFD) units shows the lightning strike data together with the weather data.

The LSS identifies four levels of lightning strike intensity. Each level has a different symbol that shows the lightning strike bearing and distance. Each symbol or "cell" is an average of all lightning strikes that occur in a specified area for four minutes. While in the MAP mode, the MFD unit show this data with the primary weather display. The data that follows shows the different levels of lightning strike intensity and their symbols.

LEVEL	LX STRIKE INTENSITY	COLOR/SYMBOL
LEVEL 1	Low	White lightning bolt without arrows
LEVEL 2	Higher	Higher White lightning bolt with down arrow
LEVEL 3	High	White lightning bolt with up/down arrows
ALERT	Highest	Magenta lightning bolt without arrows

Note:
The ALERT symbol shows the lightning strike bearing at the maximum LSS range (100 nmi).

The modes of operation and fault codes are also displayed on the MFDs. The lightning symbols remain on the display for several minutes. They must be compensated for aircraft motion and course changes. The FMS system provides the required information to support the lightning sensor system displays.

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The LSS processor is installed in the fuselage/stabilizer section. A clamp holds the unit in a mounting tray. The LSS processor weighs 6.75 lbs (3.06 kg) and operates with a +28 VDC power supply. The LSS processor supplies ±12 VDC to the amplifier circuitry installed in the LSS antenna subsystem.

The processor is mounted in the aft equipment bay at FS1100. Calibration adjustments are located on the front of the unit to allow the system to be adjusted to compensate for the aircraft specific electromagnetic interference (EMI) field.

The LSS processor receives and digitizes the low-level H-field and E-field signals (e.g., pulse width, field strength) collected by the LSS antenna. The LSS processor also receives the aircraft’s position data (e.g., pressure altitude, heading) from the integrated avionics computer 1 (IAC 1). With this data, the LSS processor calculates the bearing, distance, and intensity of the lightning strikes around the aircraft. The LSS processor transmits this data to the electronic flight instrument system (EFIS) as ARINC 429 data. The MFD units shows the lightning strike data with the weather data.

The LSS processor collects data from many lightning strikes and puts it into different cells. Each cell is an average of all the lightning strikes that occur in a specified area for four minutes. The LSS processor keeps the data of up to 50 cells at a time in its RAM. As the aircraft’s position changes, the LSS processor automatically corrects the cell’s position shown on the display. This function makes sure that the cells always show accurate lightning strike data.

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The lightning sensor is a brick type antenna which is not aerodynamic so it is installed under a composite material fairing that protects it from rain and wind turbulence. The brick antenna is encapsulated and is not repairable.

The LSS antenna is installed in the vertical stabilizer tip. It is equivalent in operation to a conventional automatic direction finder (ADF) antenna. It is an amplified antenna system that has the different antennas that follow.

H-Field Antenna

This antenna has X-axis and Y-axis loops that are sensitive to the horizontal electrostatic fields around the aircraft. Its X-axis loop collects longitudinal data and its Y-axis loop collects lateral data.

E-Field Antenna

This antenna is sensitive to the vertical electrostatic fields around the aircraft.

Self-Test Loop Antenna

This antenna receives the simulated LX test pulses from the LSS processor during the TEST mode.

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The pilot’s weather radar (WXR) control panel also controls the LSS. If the LSS is installed, the weather radar control panel includes a rotary knob that controls the LSS functions.

The LSS control knob operates as follows:

• Off – The LSS does not receive power
  
  
• Standby (STBY) – In this mode, the LSS collects (but does not show) the LX data
  
  
• Lightning (LX) Detection – This is the usual mode of operation. In this mode, the LSS collects and shows the LX data. The LSS uses symbols that give the bearing, distance, and intensity of LX strikes. It also uses legends to show the different modes of operation
  
  
• Clear/Test (CLR/TST) – This mode erases the LX data on the display and, after 3 seconds, puts the LSS in the TEST mode

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The LSS relay is installed in the junction box No. 3. It operates with a +28 VDC power supply.

The LSS relay energizes when you push the push-to-talk (PTT) switch on the high-frequency (HF) microphone. While energized, the LSS relay stops the usual operation of the LSS processor during HF radio transmissions. The high-power HF transmissions can cause the LSS system to give incorrect LX data.

Global Express/XRS

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The lightning sensor system (LSS) uses a low four frequency radio receiver (50 kHz). It also uses a loop antenna with two windings 90 degrees apart (nose and wing) to detect the direction of the magnetic field, and a component to detect the electrostatic field.

The antenna contains sensing elements to receive the magnetic and electrostatic fields produced by lightning. The relationship between the magnetic and electric fields is used to determine the range.The antenna contains a test winding which allows the processor to inject a test signal simulating lightning.

The lightning sensor processor receives the control signals from the weather radar controller, the present position and heading inputs from the FMS.The processor transmits display data to the IACs via ARINC 429. Symbols representing various lightning strikes and rates are displayed at the center of any zone of any such lightning activity.

The power input is 28 VDC at 2.5 A from the DC 1bus to the secondary power distribution assembly (SPDA). The 28 VDC input also powers a relay used to disable the processor when the HF radios are transmitting. The ground to energize the relay comes from the audio control units HF PTT lines.

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Lightning Sensor System Mode Annunciation

Lightning sensor system mode annunciations are displayed on the bottom line of the lower left-hand MFD display window. The legend LX is equivalent to the word lightning. The data that follows shows the different legends and modes.

• LX/F: Indicates that self-test has detected a fault
  
  
• LX/S: Indicates that the system is in the STBY mode
  
  
• LX/CL: Indicates that the system is in the CLR mode. This occurs for approximately three seconds after the CLR/TST mode has been selected. After this time the mode annunciation will switch to LX/T
  
  
• LX/T: Indicates that the system is in the TST mode. If a hardware fault is detected, this annunciator may be replaced by an amber failure code
  
  
• LX/I: Indicates that the receiver is inhibited by the XMIT INH input during transmission by communications transmitters. No lightning information can be received during this condition
  
  
• LX/C: Indicates that the system is in the self-calibration mode. This will revert to selected mode approximately 10 seconds after power is applied. The "C" annunciation will be removed as soon as the self-calibration process is completed, usually about eight seconds If the "C" does not disappear, the cause could be some string interfering signals that prevent self calibration or a fault in the equipment
  
  
• LX/L: Indicates that the number of computed lightning rate symbols exceeds the capability of the display system
  
  
• LX: Indicates that the system is in the normal operating mode

LEGEND	COLOR	MODE	EFFECT
LX/OFF	Green	LSS OFF	LSS OFF
LX	Amber	LSS ON	LSS ON (no ARINC 429)
LX	Green	LSS ON	Full LSS operation (usual mode)
LXmn	Amber	LSS Failure Code	'mn' is an 8-bit LSS failure code
LX/F	Amber	LSS Failure	LSS failure during a self-test
LX/S	Green	LSS Standby	LSS collects data (no LX display)
LX/CL	Green	LSS Clear	LX data erased from the display
LX/T	Green	LSS Self-Test	LSS self-test starts
LX/I	Green	LSS Transmit Inhibit	LSS OFF during HF radio transmissions
LX/H	Green	LSS Heading Invalid	No heading data input
LX/C	Green	LSS Auto Calibration	Automatic LSS calibration

Note:

• It is possible that two or more of the above situations may be true at the same time. In that case, the annunciation, which is highest on the above list, will be displayed
  
  
• All mode annunciations except LX/F may be white or green. LX/F will be amber

Lightning Strike Display

EFIS is capable of displaying up to 16 white color strike symbols. A maximum of three of the 16 strikes may be magenta color alerts. For each strike showing an LX strike intensity (level 1, 2 or 3) of other than alert, the lightning symbol is shown at the strike bearing and distance. Strike symbols outside the map data area are not displayed, except for alerts, which are displayed at the edge of the map data area.

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The lightning sensor processor is controlled by five discrete inputs from the LSS switch located on the weather radar controller. The LSP can be operational when the weather radar is turned OFF.

The power input is a 28 VDC at 2.5 A from the DC 1 bus to the secondary power distribution assembly (SPDA). The 28 VDC input also powers a relay used to disable the receiver when the HF radios are transmitting. The ground to energize the relay comes from the audio control units HF PTT lines.

There is an ARINC 429 input from IAC 1 to the processor. This brings present position and true heading data from the FMS to allow the system to compensate for aircraft turns and forward movement.

The display output to the three IACs use ARINC 429. The data stream contains range, bearing, and level data for up to three alerts and 50 rate symbols. The data contains information for a 360 degree area and a radius of 125 miles around the aircraft. The MFD displays a 120 degree sector in front of the aircraft.

The strapping configuration tells the processor that the heading information is in ARINC 429 format. The other straps are left open to let the processor know that the Azimuth display angle is 120 degrees, the input format is low speed ARINC, the positioning mode is present position, the antenna orientation is top mount and the data out speed is low speed.

There are 11 discrete wires between the processor and the antenna (AT-855). Six wires are used to bring the signals to the processor, three for the power (±12 VDC) and two for a test signal to the antenna. There are three ARINC 429 outputs to the integrated avionics assemblies (IAC) with lightning position and intensity information. This information is processed by the symbol generators and sent to the MFDs on the high-level data link communication buses.

The lightning sensor relay, located in junction box no. 3, energizes during HF transmissions to remove power from the lightning sensor receiver. This prevents false lightning symbols from being displayed on the MFD.

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In order to isolate problems in the system, the lightning sensor processor performs two types of automatic self-test. They are:

• "Power On" test
• "On Line" BITE (built-in test equipment)

The lightning sensor processor also can display various system parameters on its maintenance pages that can be useful in troubleshooting. This information is displayed directly on the MFD as detailed in the table below.

LSS MODE	ANNUNCIATION	COLOR	SIGNAL
LSS Off	"LX/OFF"	Green	LX Power is off.
LSS Interface Failure	"LX"	Amber	Activated when LX Power is on and ARINC 429 bus is inactive
Fault Code Display	"LXmn"	Amber	LX Fault Code
LSS Fault Detected	"LX/F"	Amber	LX Fault
Standby	"STBY"	Green	LXX Standby
Clear	"LX/CL"	Green	LX Clear
Test	"LX/T"	Green	LX Test Mode
Antenna Input Inhibited	"LX/I"	Green	LX Ant Inhibit
Heading Input Deselected	"LX/H"	Green	LX Hdg Invalid
Self Calibration Mode	"LX/C"	Green	LX Auto Cal
Normal Operation	"LX"	Green	LX Normal

Power On Test

When power is first applied to the system, the following tests are performed automatically:

• EPROM checksum test
• RAM read/write test
• Shared RAM test
• Configuration strap validity test
• Power supply voltage test
• System calibration

In the event of a failure, an amber LX/F is displayed in the mode field.

On Line BITE

A monitor circuit continuously monitors the operation of various circuits, such as the power supply. In the event of a failure, an amber LX/F is displayed in the mode field.

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Pilot-Activated Self-Test

In the event that the operator wishes to verify the operation of the lightning sensor processor, a special self-test function may be initiated. This test performs a full end to end verification of the system by generating a known signal in the antenna and displaying the result on the display.

The self-test is operated as follows:

• Select 50 NM or greater range
• Select CLR/TEST
• Verify that any display symbols are erased from the display

Note:
After three to four seconds, simulated lightning test pulses are sent to the antenna.

Verify that a rate 3 symbol is displayed at 25 NM and 45 degrees right. This cell will take approximately five to seven seconds to build up.

Note:
This time will be extended by approximately 15 seconds if TEST is selected immediately from OFF, due to processor initialization.

The symbol’s range may vary by as much as 5 NM if strong local interference is present.

The test symbol will degrade and vanish after approximately two minutes.

Verify that an ALERT symbol is displayed at maximum selected range, at 45 degrees right. This must remain for three to seven seconds. To restart the test, switch to LX mode and back to CLR/TEST.

When a hardware/firmware failure occurs, the indicated LX mode will be switched to an amber LX/F. If the LX system is placed in the CLR/TST mode, the actual fault code will be displayed. If multiple failures occur, the processor will cycle through each, stopping on each one for approximately three seconds.

Lightning Sensor System Fault Codes

Amber lightning sensor system fault codes LXmn are displayed on the bottom line of the lower left-hand display window. The range of the code is from 00 to FF.

Manual Calibration

The lightning sensor system can be manually calibrated to optimize system operation in the aircraft. Four correction factor switches, S1 thru S4, located on the processor front panel, are adjusted to correct for magnetic and field distortions caused by the aircraft. Correction factors for aircraft type and antenna mounting location are predetermined and plainly marked on a label, which is located adjacent to the processor unit. Switch functions are summarized as follows:

Switch S1

Switch S1 handles the nose magnetic field amplitude correction factor.

Switch S2

Switch S2 handles the software E-field gain correction.

Switch S3

Switch S3 handles the azimuth bearing correction factor. It is used to correct for magnetic field distortions caused by the airframe. This setting depends on antenna mounting location.

Switch S4

This switch controls the analog E-field gain correction factor that determines system sensitivity. Typical settings for the Global are as follows:

• S1 set to 8
• S2 set to 8
• S3 set to A
• S4 set to 7

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
A224	LIGHTNING-SENSOR SYSTEM PROCESSOR	ZONE(S) 332	34-47-01 [ GX ] [ GXRS ] [ G5000 ]
E55	LIGHTNING-SENSOR SYSTEM ANTENNA	ZONE(S) 346	34-45-05 [ GX ] [ GXRS ] [ G5000 ]
-	LIGHTNING-SENSOR SYSTEM RELAY	ZONE(S) 141	34-45-09 [ GX ] [ GXRS ] [ G5000 ]

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