Rotax 503 Rev Ouput/Inputs to ULStratomaster

[Irishman]

I searched this index for a whole weekend as well as the internet for a solution and found none.

Well here is the answer for all of you who have struggled and are still in some doubt as to why you get unstable rev pulses and the reading on the rev counter (Digital) will not give the correct readings.

After much thought and a lot of tinkering with the UL Stratomaster from MGL Avionics we were still getting unstable rev readings on the instrument while on the climb out and in level flight (7000 to 8000 rpm). A second MGL CHT, EGT instrument (New) was installed to verify the rev readings and we still got high rev counts coming through to the instrument from the engine. (This is now both instruments connected in parallel)
The CHT, EGT MGL series 1 flight instrument was added so that the engine performance could be checked using the temperatures of the exhaust and cylinder heads to verify that we were not over reving the engine which would show up in these temperatures increasing above nominal working temps.

All that was required at the end of the day was to install a 220 ohm 5 watt resister in parallel (between the grey wire from the engine and Ground (- neg) of the instrument. MGL Avionics terms this a ballast resistor. It is not called a ballest resistor as there is no such thing, it is infact acting as a ballast (simulated load) which gets rid o the noise created by the engines alternator.
All was suddenly corrected, rev readings were spot on. This was checked with a laser RPM gauge at the end of the day on the prop while at full throttle. ((indicated revs on the gauge) / (Prop Blades)) x gearbox ratio = engine revolutions

I hope this information helps somebody in the future.
Forget about all the bullshit make a plane stories I read through on the net.

Regards,

Irishman

[KFA]

Too true, suddenly I don't have to pull the seat out of my arse from worrying that I am over revving his mashine