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The M-2000C HSI explained



The Horizontal Situation Indicator HSI



The Horizontal Situation Indicator, commonly called HSI, is an aircraft flight instrument that combines a Heading Indicator with a VOR-ILS indicator.



Unlike standards HSI used in American aircrafts, the M-2000C HSI was designed to require little to no pilot input. It consists of a compass rose to indicate aircraft true or magnetic heading, a selected auto pilot heading indicator, two needles, a four-digit mechanical display, an operational mode indicator and four failure flags.



The only pilot required inputs are: Operational Mode and TACAN Offset values.



The HSI also controls the type of heading that will be used on all navigation instruments: True or Magnetic.







1. Selected AP Course indicator.

2. DME display

3. Needles

*· Needle 1 : Wide.

*· Needle 2 Thin.

4. VAD (TACAN Offset Point) input knob.

5. Compass Rose.

6. HSI mode selector

*· Cv NAV

*· Cm NAV

*· TAC

*· VAD

*· ρ

*· θ

*· TEL



Operational Modes



The HSI has four operational modes: INS/VOR Navigation (NAV), TACAN/VOR Navigation (TAC), TACAN Offset Point/VOR Navigation (VAD) and Ground Controlled Interception (TEL).



*· NAV (main INS/VOR navigation mode) : In this mode, the HSI connects with the INS and displays waypoint navigation information along with bearing to selected VOR/ILS station. This is the only mode that allows to select between true or magnetic headings, through its two sub modes:



Cv NAV : In this mode the system uses true heading. Cv stands for Cap vrai (French for True heading).

Cm NAV : In this mode the system uses magnetic heading. Cm stands for Cap magnétique (French for Magnetic heading).



The selection of Cv NAV or Cm NAV also affects the heading indicators in the following instruments: HUD, HDD, ADI.



All other following modes are part of the “Cm” category, i.e. they use only magnetic heading indications.



* · TACAN/VOR Navigation (TAC): In this mode the HSI connects to the TACAN receiver.



*· TACAN Offset Point/VOR navigation (VAD): In this mode the HSI calculates and navigates towards a point offset to the current TACAN station. The offset point location is introduced in polar coordinates, distance and magnetic bearing, by using the VAD (TACAN Offset Point) input knob.



This mode has three sub modes:



VAD: This is the operational mode. The HSI checks if it a valid TACAN Offset Point exists and calculates distance and bearing from the current aircraft position towards the offset.

ρ (Rho): This mode is used to enter the distance in nautical miles from the TACAN station to the offset point.

θ (Theta): This mode is used to enter the magnetic bearing from the TACAN station to the offset point.



Please refer to the TACAN Offset (VAD) Navigation chapter for more information on this mode.



*· Ground Controlled Interception (TEL): In this mode the HSI displays interception information: bearing, distance and interception course, towards a target. This mode is used when the aircraft is under Ground Controlled Interception (GCI).



Note : Ground Controlled Interception is not simulated in DCS and thus this mode is not operational.



HSI Information provided



The HSI needles and indicators show navigation information based on the selected mode .







TACAN Offset Point (VAD) Navigation



The HSI has a special navigation mode called VAD (Vecteur ADditionel, French for Additional Vector). The VAD is an offset point calculated from the position of the selected TACAN station. The system uses the Needle 1 (Wide) and DME (numeric) indicators. The Needle 1 and DME flags will be shown if it is not possible to engage the VAD mode.



For the VAD mode to be operational the following conditions must be met:



1. A TACAN station has been selected and the signal must be received.

2. The polar coordinates from the geographical position of the TACAN station to the offset point have been entered into the system.



When all conditions are met the HSI will navigate directly towards the TACAN Offset Point (VAD) from the aircraft position.





How to operate the VAD mode:

1. Select a TACAN station in the TACAN receiver.

2. Place the HSI in TACAN mode and check that it is receiving a signal from the TACAN station (the DME and Needle 1 flags should not be shown).

3. Place the HSI in θ (Theta) mode.

4. Enter the magnetic bearing from the TACAN station to the VAD by rotating the VAD input knob. The Needle 1 indicator will rotate towards the selected value, note that the DME window will also show the corresponding numeric value.

5. Place the HSI in ρ (Rho) mode.

6. Enter the distance from the TACAN station to the VAD (offset point) by rotating the VAD input knob. The DME indicator will start showing the selected distance. The valid values are from 001.0 to 999.0 nautical miles. The Needle 1 indicator will show the selected θ (Theta)

7. Place the HSI in VAD mode. The system will calculate the geographical position of the offset point from the current aircraft position: The Needle 1 indicator will show the magnetic bearing to the VAD and the DME indicator will show the distance in nautical miles (see the graphic).

HSI Failure Flags



The HSI has four failure flags that indicate an error condition in the HSI:



1. DME Failure : It shows a bar across the DME indicator, blocking the value shown. If it is visible there is an error in the DME value.



2. Needle 1 Failure : It shows an orange tab in the right flag window. If it is visible, then it is not possible to show the bearing to the selected navigation point/station. The Needle 1 indicator will park itself to the 135º position.



3. Needle 2 Failure : It shows an orange tab in the left flag window. If it is visible, then it is not possible to show the bearing to the selected VOR/ILS station. The Needle 2 indicator will park itself to the 225º position.



4. Heading Failure : It shows an orange tab in the bottom flag window. If it is visible, then it indicates a problem with the heading gyro and thus the heading value shown in the HSI and other heading indicators is not reliable. If shown it is recommended to use the auxiliary heading gyro. This information should appear in the next update: __________________

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