MGL Avionics Stratomaster Ultra Horizon XL Owner’s manual
Page 56
highlighted entry that is shown is NOT the setting in the SP-3, only the setting that you want to
send to the SP-3. The SP-3 stores the setting in permanent memory, the setting is not lost if you
remove power from the unit.
Like the “Bump” filter, the “Slew” filter also has five settings:
Lowest, Low, Medium, High, Highest.
This filter setting affects the speed at which error corrections take place.
Good settings are usually Low, medium or high.
This filter setting interacts somewhat with the Bump setting. Should you find your installation
tends to accumulate errors quickly (for example you may have unavoidable vibration affecting the
sensors), set the error correction speed higher.
Do not set the error correction speed unnecessarily high as this may degrade your systems ability
to correctly detect very slow entries to banks.
Finding the right filter values
Once good filter values are found, they are rarely if ever changed.
Good filter value selection will result in the system remaining in accelerometer mode (indicated
on your screen) for most of the time during straight and level flight.
Slow entries into banks are the most critical factor, so try these in calm conditions. Bump factor
too high or Slew factor too high (or both too high) may result in bad detection of this maneuver.
Select the Slew factor such that any errors that have accumulated during a full 360 turn at 30
degrees of bank are corrected quickly after you roll out straight and level.
Attitude mode
Here you can select the type of attitude calculations you want to use.
The choice is between “IMU” and “Mattitude”. The display shown indicates the current mode of
operation if you have the SP-3 connected.
Please read the documentation on the SP-3 for detail of which mode you should choose.
“Mattitude” is an experimental system at this point in time, “IMU” is the normal way a strapdown
artificial horizon works.
“Mattitude” will not work correctly if your aircraft has a significant effect on the direction and
strength of the measured Earth magnetic field.
Please note that before you can use this mode, you have to set the magnetic inclination at your
location (described below).
Attitude determination modes
The SP-3hc unit provides the user with a choice of two different modes to obtain aircraft attitude
(bank and pitch).
IMU attitude determination
This mode is the traditional IMU consisting of three gyros and three accelerometers. Gyros
provide rate of turn information while the accelerometers are used to vector gravity in order to
compensate for gyro drift and also to set the initial orientation of the quaternion.
Magnetometer based attitude determination
This method uses the magnetic vector direction in three dimensions to obtain a relative attitude
that can be used as bases for determining attitude relative to the earth surface.
The SP-3hc will automatically obtain the magnetic inclination (dip angle) regardless of its own tilt
relative to the earths surface. This measurement needs to be done very accurately. The SP-3 will
perform this measurement about once every 10 seconds provided the aircraft is providing a
stable enough platform. (benign flight conditions).
