Sky Dart Autopilot Modes
For the sophisticated space pilot.
Table of contents
The Autopilot Control Panel
Like many small aircraft, the Sky Dart has a basic autopilot control panel just below the pilot’s primary window.
The Sky Dart autopilot control panel
Autopilot Functions In A Nutshell
| Autopilot Mode | When Activated | When Deactivated |
|---|---|---|
| RATE MODE | joystick commands a rotation rate | joystick commands a rotation acceleration and deactivates HOVR MODE |
| HOVR MODE | ship holds current vertical rate and activates HSPD MODE | deactivates HSPD MODE |
| HSPD MODE | ship holds current horizontal rates and deactivates PROP CTRL | deactivates PROP CTRL |
| X10 | HSPD joystick inputs are $\pm$ 10 ($\frac m s$ in PROP MODE, otherwise $\frac m {s^2}$) | HSPD joystick inputs are $\pm$ 1 ($\frac m s$ in PROP MODE, otherwise $\frac m {s^2}$) |
| PROP CTRL | joystick: horizontal rates in $\frac m s$ | joystick: change in horizontal rates in $\frac m {s^2}$ |
The following sections cover each mode in more detail.
RATE MODE
When the Sky Dart is powered up, the autopilot has RATE MODE active by default. With RATE MODE off, the joystick directly operates the attitude control thrusters. The ship is very difficult to control RATE MODE off, and the only time it should be deactivated is if there is a fault in the autopilot.
RATE MODE ON
With only RATE MODE ON, any rotational motion of the ship can be stopped simply by letting go of the joystick.
RATE MODE OFF
HOVR (Hover) MODE
Hover mode commands the joystick and throttle to zero out any acceleration of the ship, while maintaining the current vertical and horizontal rates or speed. The vertical speed is shown in the VS seven-segment display on the autopilot panel, while the horizontal speeds are shown by the two green diamond “bugs” on the cross-pointer display:
Vertical speed and altitude in HOVR mode are always computed relative to the local terrain and are subject to the maximum range of the radar system (2000 m) and a bank or pitch angle of 45 degrees.
Typical Transition from HOVR OFF to HOVR ON
The following diagram shows how the ship’s dynamic state changes when HOVR mode is engaged.
Engaging HOVR mode captures the current vertical and horizontal speeds of the ship, then tries to maintain them. Once engaged, you can change the captured speeds using the round vernier throttle knob and the joystick.
Changing Vertical Speed While HOVR MODE is Engaged
While HOVR MODE is ON, use the vernier throttle to adjust the vertical speed. If you adjust the vertical speed to be ZERO, then the autopilot will also capture the altitude above terrain, and will continue to make adjustments to hold the captured altitude.
The following graphic shows an example of using HOVR mode to slow descent and hold a true hover at 308 m above the surface.
HSPD (Horizontal Speed) MODE
Engaging HOVR mode automatically engages HSPD mode and captures your current horizontal speed. When HSPD is engaged, disengage it again by pressing the HSPD MODE button; HOVR mode will not be affected. Regardless of the HSPD mode, disengaging HOVR will force HSPD OFF. In other words, HSPD requires the vertical speed to be controlled by autopilot at all times.
While HSPD mode is ON, the joystick moves the horizontal speed setpoint, shown by the position of the two green diamond speed bugs on the cross-pointer display. If PROP CTRL is OFF, then the position of the joystick corresponds to the rate at which the speed bugs move. If you release the joystick, the setpoint stays where it is. If you push the joystick fully forward, the forward speed setpoint will increase at a constant rate. If you release the joystick again, the setpoint will freeze at its current position.
The following graphic shows an example of using HSPD mode to slow the horizontal speed from 8 $\frac m s$ to 4 $\frac m s$:
Although there is no speed limit for horizontal flight in HSPD mode, flying over rough terrain at high speeds will cause the autopilot system to disengage without warning if it is unable to compensate for rapidly changing height above ground level.
X10
Turning X10 on when HSPD mode is on increases the joystick sensitivity by a factor of 10. In PROP CTRL mode, it changes the full scale joystick deflection from 1 $\frac m s$ to 10 $\frac m s$.
PROP CTRL (Proportional Control)
Proportional control mode changes how the joystick moves the horizontal speed setpoint bugs on the cross-pointer display. With PROP CTRL engaged, the setpoint bug position will track the joystick position. If the joystick is released, then the setpoint speeds will both be zero. If you disengage PROP CTRL while the ship is still moving sideways, then HSPD will use that horizontal speed as its new setpoint.
When PROP CTRL and X10 are both active, full deflection of the joystick will command a horizontal speed of 10 $\frac m s$. If X10 is off, then the maximum horizontal speed you can set is 1 $\frac m s$.
Landing With PROP CTRL
One of the best uses of PROP CTRL is during the final approach to a landing pad. The final approach should be at a low (1-2 $\frac m s$) vertical and horizontal speed. Once the ship is over the center of the pad, engage PROP CTRL to arrest all forward motion; the ship will then descend straight down until contacting the pad or terrain.
Autopilot Failures and the WARN Lamp
If the autopilot experiences flight conditions (such as high speed flight over rough terrain) that it can’t manage, it will automatically disengage HOVR mode (and by extension, HSPD and PROP modes). In this event, the WARN button on the autopilot panel will illuminate, and a loud audible alarm will sound in the cockpit. Pressing the WARN button silences the audible alert. Pressing WARN when it isn’t active will activate the audible alarm (serving as a test of the system). Press the button a second time to silence it.
When the autopilot disengages, the throttle remains in whatever position it was in when the failure occurred. The RATE MODE will remain engaged, and the ship will stop rotating. Your first priority in this event is to assess the situation and try to restore controlled flight manually. If you were moving with a high horizontal speed, try to slow the speed manually before attempting to engage HOVR mode again.
The three priorities of any pilot are always aviate, navigate, and communicate. Don’t worry about silencing the alarm until you are in control of your spaceship (always prioritize aviate!).