MGL Avionics Stratomaster Ultra “L” Owner’s manual
Page 46
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).
Fuel flow calibration
This setting is used to calibrate the fuel flow sender if you fit such a device. Increase the
setting to lower the fuel flow reading and vice versa.
The value of 208 corresponds to the recommended setting for the RS 256-225 liquid flow
sender. Using this setting and a correctly installed sender you should expect an accuracy of
about +/- 3% maximum error.
This factor will affect the instrument’s range and fuel bingo time estimates so be careful
should you choose to change this setting. Should you have difficulty in obtaining the correct
fuel flow indication your problems are most likely due to vapor bubbles trapped in the fuel
sender housing. Make sure you install the sender in such a way that it is not possible for
bubbles to remain trapped in the sender housing.
Rev setup: Pulses per 10 revs
Use this function to calibrate your rev counter. A value of 60 is used for most two-stroke
Rotax engines based on the Ducati DCDI system (6 pulses per rev). Rotax 912/914 engines
produce 1 pulse per rev so the correct setting would be 10.
Select the value according to your engine’s tach generator output for all other engines.
Should you have an engine without a tach generator such as a VW, we suggest that you try a
pickup using a wire looped tightly about 20 times around one of the spark plug leads. (See
installation manual for further details on this method). A spark is generated every second
revolution per cylinder on a four stroke engine so you should enter a value of 5 in this case.
You can also try pickups directly from the switched end of the ignition coil (points). This may
give you a better signal. In this case the factor to be entered will depend on the number of
cylinders. You should find two cylinders firing for every revolution in a typical four-cylinder
four stroke engine so this would give you a factor of 20 to enter.
Take-off revs
This is the rev limit to use for automatic take-off detection. Take-off detection is relevant for
the automatic logbook. The instrument uses a combination of take-off revs exceeded and
airspeed above 30 mph (48 kph or 26 knots) to detect the start of the flight.
Note: Once a flight is started, revs are ignored. Only airspeed is relevant then.
Hobbs revs
This is the rev limit above which engine running time is added to the hobbs meter and
maintenance meter. This setting allows you to choose whether or not to add engine idle
speed time to the hobbs meter. Should you wish to have engine idle count towards the hobbs
meter time, set the Hobbs revs value to less than your normal engine idle speed.
