Dynon Avionics SkyView Autopilot In-Flight Tuning Guide - Manual (Page 13)

SkyView Autopilot In-Flight Tuning Guide - Revision B 4-1
4. Pitch Axis – IAS Hold Procedure
Overview
The goal of tuning IAS Hold is to give the AP the best possible pitch axis performance. Crisp
speed control is a prerequisite for good altitude and glideslope control. Although IAS hold is
only available in EXPERT mode, tuning will benefit SIMPLIFIED mode greatly, so even if you
don't intend to use EXPERT mode, this procedure is essential for good performance.
The procedure which follows can be used both for initial tuning and for troubleshooting
problems which may arise in your system. Like any checklist or procedure, be sure to follow
each step.
The autopilot controls should be changed to EXPERT mode
(SETUP MENU > AUTOPILOT SETUP > AUTOPILOT CONTROLS)
The ALT bug should be set to an altitude many thousands of feet above or below
the intended flight testing altitude. This is to keep the autopilot in IAS Hold mode
throughout the procedure, and prevent the autopilot from capturing the target
altitude.
The Pitch Axis IAS Hold tuning process can be summarized as follows:
Increase or decrease airspeed command by 10 knots, and observe the results. The AP should
promptly change pitch to change speed, and smoothly reach the commanded speed with little
or no overshoot (above the target if increasing; below the target if decreasing).
If the AP is slow to respond to the airspeed changes, increase the PITCH SENSITIVITY and watch
for improvement. In some cases this may require a fair amount of increase, but be cautious
about changing too quickly. Sensitivity adjustments alone may not completely eliminate
overshoot. If increasing sensitivity no longer improves performance, PITCH GAIN may be used
to fine tune IAS Hold. Too much sensitivity may cause AP responses to be "twitchy". Reduce
PITCH SENSITIVITY if this occurs. Too much PITCH GAIN will result in a rough ride.
In particular, if the autopilot cannot keep up with the flight director pitch command bar, PITCH
SENSITIVITY should be increased. At some point the AP will track the command bars, but follow
behind them. PITCH GAIN will reduce the gap.
Caution: Large changes in PITCH SENSITIVITY with the autopilot engaged can result
in large servo movements.