means approximately ¼ of thrust. On small engines with a high idle to full power rpm ratio, or
in a high drag/low power planes, often only the last 1/3 of the throttle stick produce significant
thrust, with the low half stick travel being not used. Although that with current digital TX the
pilot can modify the throttle curve to suit his needs, three throttle curves have been added to
simplify the setup for most of the installations. These curves are selected under the RADIO
menus:
FULL EXPO:
Mean linear RPM, it is the default setting and the mode used for all previous
software versions. Thrust develops exponentially, and it is the recommended curve for big
engines or/and high thrust/weight ratio planes, as it ease the control in low power used during
taxi.
LINEAR:
Mean that the thrust develop linearly with the throttle setting. Could cause difficult
taxi, as it would be difficult to fine adjust the power at low settings.
HALF EXPO:
An intermediate setting between the other two modes.
Throttle curves can be changed while the engine running, so you can leave the throttle at a
given position and switch between the curves to see the difference.
Acceleration and deceleration settings
Under the “RUN” menus is possible to change the acceleration and deceleration times. The
engine is supplied and tested from factory ready to use and usually these settings should be
correct for normal use. However the user can modify these default settings to allow the engine
to run optimally in different conditions.
Leave the acceleration and deceleration in “fast” mode when using the engine with kerosene
and at ambient temperatures below 25ºC and elevation below 500m. If diesel fuel is used, or
ambient temperature is over 25ºC or altitude is over 500m, then the engine could experiment
difficulties in accelerating. In these cases, try to set the acceleration to “normal”, “slow” or
“very slow” to find a setting where the engine operate normally. It is much better to have an
engine than respond slower to throttle changes than one that just stop when asked to
accelerate faster than possible in difficult ambient conditions!
Exhaust tubes
The size and placement of the exhaust tube is not an exact science. The optimum tube
diameter and the gap between the engine exhaust and the tube intake is largely dependent of
the airframe. An slow airframe with big intakes will benefit of larger exhaust diameter and
larger gap, to get the maximum static thrust possible, while a fast airframe, with small intakes,
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Summary of Contents for Merlin M122NG
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