©2010 Skookum Robotics, Ltd
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Symptom
Problem & Solution
Helicopter precesses in hover (a
motion like a child’s spinning top
as it slows down). Gets worse
with higher Hiller gains.
Interaction between the Elevator,
Aileron, and Yaw axes. Check that the
SK720 gyro is mounted correctly. Also
check rotor head phasing.
SK720 initializes properly but
there are violent twitches in
hover, in aileron/elevator or
rudder (yaw).
Electrostatic buildup on the tail belt
drive. Ground the tail boom to the
frame, and use a silicon-based lube on
the tail belt.
In self-leveling mode, the heli
tends to wander.
The vibration level of your heli may be
too high. Improve the main and tail
rotor’s balance, and/or move the SK720
closer to the heli’s C of G.
Heli yaws wildly in one direction.
Check that the sense direction for the
rudder (yaw) is correct, and that the tail
servo moves in the right direction.
Tail oscillates even when the
gain is low.
Friction and/or slop in the tail linkage.
Tail twitches a bit in hover
and/or gain can’t be set very
high without wag.
Too much vibration is getting into the
unit. Make sure its case isn’t contacting
the heli’s frame, and the wires leading
to it are a bit loose. For larger
helicopters, you may want to use a
separate power bus to allow lighter
wires leading to the unit.
Tail gain can’t be set high
enough without oscillation (wag)
Check if the tail boom is stiffly braced,
and that the full range of tail blade pitch
uses most of the servo’s motion.
Faster/stronger servos may help.
Tail doesn’t hold very well in
wind or backwards flight.
Set the tail Hold gain higher.
Helicopter slowly yaws in hover.
Make sure that “auto trim at init” is
turned on, and/or increase the
deadband value for rudder.
Piro starts/stops in one direction
are good, but the other direction
bounces.
Set the start/stop acceleration values
for the tail to be lower for the direction
that bounces.
©2010 Skookum Robotics, Ltd
54
Appendix A: Specifications
Dimensions
39x30x14mm
Weight (without cables)
18 grams
Operating Temperature Range
-10c to +45c
Operating Voltage
3.6 to 10 VDC
Power Consumption
75 mA
PWM Input Signals
6 Channels (900-2100 us)
Servo Output Signals
8 Channels (760, 960 or 1520 signals)
Servo Options
Analog or Digital
Setup
USB interface, or SK-LCD Terminal
Field Gain Setting
Gain channel inputs
