Wren 44 Gold Helicopter Owners Manual
Page 31
If the engine slows down or makes smoke at switchover but keeps going, increase the value
for “
engine min flow
” as the flow is not quite high enough to make a successful switchover.
At the end of “switchover”, burner turns off at around 20,000rpm, and “fuel ramp” begins.
Engine continues accelerating and starter turns off as it passes 30,000rpm.
(At this point if you have no rotors fitted and are just doing a start test, you must
terminate here - trim down to stop)
The gearbox output shaft may start spinning after about 20k upwards, so be ready for this. If the
engine slows below 30,000rpm at this time the starter will automatically come back on to bring the
speed back towards 32,000rpm. The clutch should be disengaged at this point but may be
dragging enough to exert some torque to the rotors – be ready for this. If it becomes too much then
shut down the engine immediately by moving trim to off.
Engine arrives at 55,000rpm - idle, (screen shows “Running”). You now have control of
engine via throttle stick.
In a helicopter installation starts are usually carried out without the display plugged in, due to
the hazard from the rotor blades, but providing the engine is run
gently,
test starts and low
power runs can be carried out with head loaders in position of the regular rotor blades.
Watch out for the tail rotor in this instance.
Once the engine is running, leave it idling for 30seconds or so to allow a flow of lubrication to be
established to the gearbox before throttling up. You should see fuel travelling along the lubrication
tube to the gearbox in regular droplets.
At any time the start can be terminated by lowering stick and trim to zero. The
throttle stick can then be used to switch the starter to clear/cool the engine.
If this is your first flight test, ease the throttle stick forward gently at first (no rapid slams) to
allow the clutch to start to grab and then hold while the transmission picks up. Be aware of
the swing of the tail and be ready to correct for this. As you advance the throttle you will fell
the heli become light on its skids and this is the point to ask yourself if the rotor speed looks
about right. If the pitch is coming in too fast you might need to stop and adjust your
transmitter to raise the throttle curve points, or to drop the pitch curve downwards. Either
way, at the point of lift-off the rotor should be going plenty fast enough to ensure enough tail
rotor power and a stable rotor plane. There is no point going further if this is not right.
The turbine power increases rapidly as the rpms rise upwards so do not try to fly on too low
an engine rpm or rotor speed. Once in the hover the throttle curve will be shallow as only a
small increase in throttle will give a good increase in torque for the rotors. Take your time
and tune the settings carefully. Always land and throttle down to idle or stop, before making
any adjustments.
If you use a throttle-hold switch, you may need to slightly increase the acceleration /
deceleration period setting (in “RUN” menu) as the ECU is set up to follow a transmitter stick
throttle command whereas a throttle-hold is an instant up/down control. This rapid control
can sometimes cause the engine to flameout when switched down to idle. The longer
deceleration time has little effect during flying but should eliminate any problem.
