MGL Avionics Stratomaster Ultra Horizon XL Owner’s manual
Page 36
Calibration Menu
The calibration menu contains functions to calibrate important sensors.
Airspeed calibration
This function is used to calibrate the airspeed reading. It works in % relative to a nominal
value. Your calibration certificate will give you the setting required for correct reading if no
external airflow factors are present. In many aircraft installations it may be required to correct
the reading to cater for errors created by the airflow around your aircraft.
You can use the + and – keys to change the calibration factor.
Altimeter calibration
This calibration is done at the factory using very accurate references. It is not normally
required to change this setting. You may do so if you feel that you would rather use another
reference, like your local airfield’s elevation according to survey maps.
Be aware that generally survey maps and GPS readings may not give you the expected
readings and are subject to small errors. For example, your GPS receiver may be using a
different datum of reference to the survey maps.
The value entered here is a correction factor that is entered during calibration of your
instrument. This factor is shown on your calibration certificate.
At sea-level, one unit corresponds to an air pressure difference as expected for a 7 ft (2,1 m)
change in altitude. At 5 000 ft (1 524 m) MSL this corresponds to about 10 ft (3 m). A
positive correction factor will decrease the altimeter reading and a negative factor will
increase the reading.
Please do not confuse this setting with the QNH (local pressure) setting available from the
main display (+ and – keys).
VSI calibration
This is a technical function that is used to calibrate your VSI to read exact rates of climb or
decent. This function works as a percentage of initial reading. The default setting for this
function is 100%. Increasing this value increases the VSI reading and decreasing the value
decreases the reading.
Suggested calibration method.
After you have installed the instrument, perform a calibration flight. This should be done in
very calm conditions. Turbulence and thermal activity will make accurate calibration
impossible. Many areas have ideal conditions during early mornings or late afternoons.
Place the instrument in “feet” units mode for ease of calibration.
Take your aircraft to a few thousand feet above ground and start a glide with a low power
setting. Take a stopwatch and when the glide is stable (stable VSI reading) start the
stopwatch. Take note of your altimeter reading at the same time.
