Terrain Following Radar

Terrain Following Radar
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Cockpit art courtesy of Cockpits.nl

Terrain Following Radar (TFR) is a system which allows the autopilot to control the aircraft very close to the ground. It uses forward-looking radar and your radar altimeter to paint a picture of what the terrain ahead looks like, and sends this information to the autopilot to allow it to fly the aircraft in a straight line at a constant altitude over the ground. It is called "terrain following" because it maintains the same radar altitude regardless of the actual shape of the terrain - therefore you will climb over hills and descend into valleys while using TFR.

TFR is generally used for low altitude flights because the computer can react faster than the pilot to changing terrain, and better maintain a constant altitude. Wikipedia has an article on TFR.

Operation

The TFR has its own MFD page which is used to control the system. It can be accessed by selecting TFR from the MFD menu. The page shows the current radar picture of the terrain ahead, as well as several OSBs which are used to control the system's functionality. The OSBs are summarized in the table below.

To engage the TFR autopilot, first get the aircraft on the heading you want to fly (you cannot change heading while TFR is active). Select the mode and altitude you want to use, and then press the ON/OFF OSB to switch the system on. The autopilot will take over control of the airplane and fly in a straight line until you shut off the system.

Abbreviation Description
NORM The far left button on the top row shows the currently selected mode. You can press this OSB to cycle through the modes, or directly select the mode you want from the left hand row. See below for more information on each mode.
HARD This OSB cycles the ride type. The available options are "SOFT", "MED", and "HARD". If you select a harder ride type, the autopilot will more aggressively follow the terrain, while in soft mode it will be more gentle.
ON Use this OSB to toggle the TFR autopilot between ON and OFF.
CHN1 In the real aircraft, this cycles the radar channel which is used for TFR. This is not implemented in Falcon.
1000 / 500 / 300 / 200 / VLC Select one of these OSBs to choose the altitude you want the aircraft to follow. The autopilot will attempt to maintain a radar altitude equal to your selected value. VLC stands for "Very Low Clearance", and should only be used over flat terrain or open water.
NORM This is the "normal" TFR mode.
LPI LPI stands for "Low Probability of Intercept". In this mode, the radar only scans for terrain. It should only be used if you are not expecting enemy aircraft.
STBY Puts the TFR into standby (not operating) mode.
WX This OSB is not implemented. It is used to set the weather mode for use in inclement weather.
ECCM This mode is used to reduce radar emissions. It is also not implemented.
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