VSI cal
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.
Continue the stable glide for one minute exactly. After the minute has finished, take another
reading of your altimeter.
Example:
VSI reading during stable glide: -400 ft/min
Start altitude: 2500 ft.
End altitude: 2050 ft.
In the above example the VSI is under reading by about 12%. Set your VSI calibration to 112% to
cancel out the error.
Zero ASI/VSI
This setup allows your instrument to measure the zero airspeed reading of the airspeed sensor
and set a calibration value internally for this. This is equivalent to some mechanical airspeed
indicators that have an adjustment to set the needle to zero when the aircraft is not moving.
You would use this function occasionally if you see an airspeed reading when the aircraft is at
rest. This may be caused by aging of the built in pressure sensor or related electronics.
When you perform this function, please make sure that no wind is blowing into the pitot tube as
this would result in an incorrect internal calibration.
This function also resets your VSI to zero. For maximum accuracy this should be performed on a
wind still day.
You may find that it is difficult to zero the VSI accurately if you perform this inside an aircraft
hanger if there is any wind outside. This is because the buildings internal pressure will vary
greatly with the winds airflow. The VSI is a very sensitive instrument.
KFactor
The K-Factor is the number of pulses generated by the fuel flow sender for one liter of fuel. The
dual range fuel flow sender supplied by MGL Avionics has a K-Factor of 7000 in the low flow
mode (jet installed) and 1330 for the high flow mode (no jet installed).
You can use the K-Factor to calibrate your fuel flow sender.
The recommended procedure would be: