How to ARRT
The Altitude / Range-Range Rate instrument provides feedback during landing (and, optionally, launch) operations, as well as during rendezvous / docking operations in orbit.
The ARRT consists of the ARRT data display, the ARRT MODE selector switch, and the ARRT ERR error indicator.
The ARRT MODE switch selects the mode the display is operating in:
- STBY: The ARRT is in standby mode. The backlights are off and the data strips return to zero.
- ALT: The ARRT is in Radar Altimeter mode. The backlight is enabled. The RANGE/ALT strip displays altitude above ground, and the RANGE RATE/ALT RATE strip displays vertical speed based on radar telemetry. The ALT and ALT RATE legends are illuminated.
- RNG: The ARRT is in Range / Range Rate mode. The backlight is enabled. If there is a target, the RANGE/ALT strip displays the distance from the target, while the RANGE RATE/ALT RATE strip displays the approach or departure velocity. If there is no target, the strips return to zero. The RANGE and RANGE RATE legends are illuminated.
The ARRT data display consists of two vertical bar strips. The left strip has the legend RANGE/ALT. It displays the range to target or altitude above ground as specified by the mode switch. This strip can report distances of up to 5000 meters. The right strip has the legend RANGE RATE/ALT RATE. It provides the closure/departure rate to the target or the vertical speed, depending on the mode.
The ARRT ERR flag is illuminated when the MODE switch is set to RNG (range) and there is no target currently being tracked.