Servo type
The SL720 supports two
This is also set in the Quick-setup routine, but for convenience is also included in this menu. Care should be exercised in
turning the Super/digital facility ON as standard servos are not able to handle the high data rates may be damaged by being
used with the DS mode. They may also malfunction in flight.
If in doubt leave this parameter at ‘standard’
Vibration filter
This parameter is also accessable via the quick setup routine and controls the primary noise/vibration filter in the SL720. The
default state is with this filter OFF. However, in high vibration environments where small disturbances of the tail are visible
in the hover this filter may provide an improvement at the expense of a reduction in the achievable transmitter gain. Where
possible it is better to resolve the vibration issue with the machine. If the disturbances increase with the use of the filter then
they are probably due to fluctuating power delivery from the engine which should be resolved and the filter returned to the off
state.
The Mode 0 and Mode 1 panels
(Yellow and red panels)
The two Flight Mode setting sub-menus are identical and provide control over the following parameters that have independent
values for each of the two gyro modes. The three gain terms work in conjunction with the gain value set from your transmitter.
Stick Dead-band
This feature is helpful in aerobatic as it reduces the accuracy of stick centring required. The amount that pilots find helpful
depends on flying style and the manouvres being performed. As a general rule high values are useful for aerobatics and lower
values for hovering manovres.
Linear Stick Sensitivity and Exponential Stick Sensitivity
The yaw rate demand curve for each flight mode can be fully and independently adjusted to give exactly the stick 'feel' you
want. The linear sensitivity has most influence on the feel near mid-stick. If, once you have the stick deadband you like, the
model feels too 'dead' around mid-stick then increase this value. Conversely, reduce this value to reduce the sensitivity to small
stick deflections. The Exponential sensitivity has little effect near to mid-stick but has an increasing effect towards full-stick
deflection. By default gyro modes 0 and 1 have the same values for these parameters. However you can give different values
for the two modes so that the stick feel changes as you switch between the two gyro modes. Further tuning of the stick feel can
be obtained from the rudder rates, travel adjustments, and exponential on your transmitter.
Pirouette start rate
This parameter is designed to match the gyro’s expectation of the helicopter’s speed of entry into pirouetes with the machines
actual ability. The value displayed relates to the rate of yaw acceleration the helicopter will generate when maximum tail rotor
pitch is applied. The default value (4500 deg/s/s) is typical of a well set-up aerobatic machine. The weight distribution in the
helicopter is important to the reaction of the model (the closer the weight is concentrated near the main shaft the better).
While this is substantially fixed for a given machine all the following factors (in order of effectiveness) will increase the
reaction speed of the helicopter:-
Longer tail blades
(most effect)
Higher tail rotor rpm (by gearing or head speed changes)
Greater tail pitch ranges
Broader chord tail blades
(least effect)
To optimise the value for your machine look at the quality of the entry into fast pirouettes (using full stick). The optimum
value is the highest value for which the entry to fast pirouettes is smooth. If you find that the model ‘whips’ at the start of the
pirouette then the value is too high. By ‘whip’ we mean that the helicopter accelerates to too high a pirouette speed before
settling back to the correct pirouette speed.
Pirouette stop rate
This parameter matches the gyros expectation to the helicopter’s ability to stop from pirouettes. In general the optimum value
for this parameter will be the same or slightly (say 10%) higher than the pirouette start rate obtained above. It is susceptable to
the same influances as regards tail blade size etc as the pirouette start rate.
Acceleration Gain
This parameter allows the gyro to look at the rate of change of the yaw speed. With high performance servos and slop-free
linkages this parameter is not needed for good performance. However we have found values of about 120 to be useful when
the gyro is used in small electric helicopters. In these cases see also the Heading lock gain. Please note that excessive
Acceleration gain can soften stop performance and increase servo power consumption.
Conventional gain
This sets the degree of rate damping provided by the gyro, and is like the gain on an ordinary (non-heading lock) gyro. It still
provides the primary stabilising effect of the gyro. Except for special applications (e.g. camera stabilisation) you will need
some degree of conventional gain. You may wish to experiment with adjusting the relative amounts of Conventional gain and
Heading Lock gain. In doing so it's worth considering the tail as if it's controlled by a spring and damper combination. The
Conventional gain acts as the damper and the heading lock gain acts as the spring. With too little conventional gain for the
amount of heading lock the tail will tend to oscillate every time it is disturbed (e.g. by turbulence)
