GRAUPNER NH90 Bedienungsanleitung Seite 64

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NH90
6.2 Adjusting the motor
Please be sure to read the operating instructions supplied with your motor!
The correct matching of collective pitch and throttle when the helicopter is hovering is of crucial
importance to the model's flying characteristics and performance. For example, if the pitch of
the main rotor blades is too high, the motor may not reach the rotational speed intended, and
this may cause you to think that the motor is not powerful enough for the job. The fact that the
motor will overheat and thereby lose more power tends to reinforce that idea. For this reason
first set the hovering collective pitch value exactly as described earlier in these instructions, then
match the motor settings to that.
Although most motors nowadays are supplied with the carburettor adjusted to approximately the
right settings, final adjustment of the needle valves can only be made under practical test
conditions. Most motors now feature twin-needle carburettors, and in this case the starting point
for adjusting the idle / mid-range needle is to screw it in to the point where it just dips into the
needle valve on the opposite side when the carburettor is half-open.
Typical twin-needle carburettor
For your first attempt at starting the motor open the needle valve 1½ to 2 full turns from closed,
connect the glowplug to the plug battery and start the motor by engaging the adaptor on the
electric starter in the teeth of the fan and switching the starter on.
Caution: when the motor starts withdraw the electric starter from the fan socket
immediately, otherwise you could damage the model!
When the motor is running, slowly increase throttle/collective pitch. If the fuel mixture is too
„rich" and the model fails to lift off, close (screw in) the needle valve in small stages. In order to
set the motor correctly for hovering you will need to adjust the idle needle, which also governs
the mid-range settings. Note that any adjustment you make here is also influenced by the
primary needle valve setting. Carefully close (screw in) the idle needle until the motor runs
smoothly at hover, without any tendency to stop through too rich a mixture. If motor speed is
then too low, increase the hover throttle setting at the transmitter. Never attempt to increase the
motor speed for hovering by setting the idle needle too lean. The final needle valve setting can
only be made with the model flying under power with „full collective", and for this reason you are
bound to start by „feeling your way" slowly to the correct setting.
If in any doubt, always set the mixture on the „rich" side. Initial hovering flights should
always be carried out with the motor set distinctly rich.
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