Wren 44 Gold Helicopter Owners Manual
Page 32
After running
After a test start, lower stick and trim to zero for cooling.
After landing from a flight, leave the engine for 30 seconds at idle for temperatures to
stabilise before returning the trim to off to shut down the engine.
ECU will spin engine in short bursts until the temp reading goes below 100’C where it will
stop. If temp rises above 100’C again ECU will spin the engine again until below 100’C.
Once cooling is complete display shows “Stop”.
The engine cannot be re-started until the radio has been turned off and back on again to
reset the ECU.
You can turn off receiver and transmitter and disconnect LiPo battery, if this is the last run for
a while, or you need to recharge.
Never recharge a LiPo whilst installed in a model.
Setting the throttle curve
If you have not already set the pitch curves for the model, a good starting point for hovering
and circuits is:
Low Stick : 3-4 degrees of pitch
Mid Stick : 5-6 degrees of pitch
High Stick : 10 degrees of pitch
You can fine tune these later on to suit the model and achieve the desired feel.
Before we go into how to set up the throttle curve for our turbine helicopter, we need to
remember that turbine engines respond to throttle changes in a different way from their IC
counterparts. Whereas an IC engine will speed up and slow down relatively quickly, a turbine
engine takes longer to make RPM changes at the low end of the throttle range but much
faster at the high end, so your throttle curve needs to reflect this. The curve should be fairly
flat with no sudden changes of angle.
A good starting point to set up a throttle curve is to set an initial curve like this.
Low Stick : 0%
Mid Stick : 60%
High Stick : 100%
For most turbine flyers a peak preset turbine speed of 175,000 RPM is more than sufficient,
so leave your turbine ECU set to this speed for now. In checks on ECU’s on engines in for
service we find most fliers actually only run their engine at around 160krpm maximum even
when set for 175k. remember to actually run at 175k your throttle stick would have to be
asking for 100% throttle – not often with a heli as you soon run out of sky!
Most modern computer radios give 5 throttle points, so there is another value either side of
the mid stick position. You can set these points quite closely to the mid stick value. Set these
provisionally at 50% at the ¼ stick position and 70% at the ¾ stick position. We’ll come back
to this in a minute.
