Pilot Authority Mixing
This should
not
be used with the ICG400 gyro.
Tail rotor dynamics
To realise the full benefit of the ICG400 it is important to have a basic understanding of the dynamics of the tail rotor system. It is a common
misbelief that the higher the electronic gyro gain is, the better the system will work. Whilst this is generally true, the electronic gain is only one
part of the tail rotor system and of equal importance is the amount of tail pitch range available, and the tail rotor disk size. The disk size is also
related to the tail rotor speed. Of course there are other influences on the tail system but these are the most important and can be grouped
together as mechanical gain.
If the mechanical gain is not correct, then the gyro will not be able to function to its best ability. For this reason it is important to select the
correct size servo arm that will give maximum tail pitch movement without stalling the servo. In most helicopters this will be an arm of between
15 and 20 mm radius. Note: As the servo travel limits are set during the auto setup routine, increasing the rudder travel adjustment will not
increase the servo throw as this is limited electronically in the gyro. The rudder travel adjustment is used instead to adjust the rotation rate.
Tail blade size
The correct length of tail blade can only be selected by flight testing. There are 2 types of test to ascertain the correct size:
1) With the model in the hover at its normal flight rpm, making sure the gyro is in Heading Lock mode, make a rapid vertical climb for 50 to 60
feet: there should be no discernible rotation of the model. If the tail does not maintain its position this is a good indication that the diameter is
too small. Note: if the model is over pitched and there is a noticeable drop in rotor rpm during the climbout, then this will invalidate the test as
the tail would probably not be able to cope with this situation regardless of the setup.
2) This test is only really necessary for those who wish to do advanced aerobatics/3D flying and should only be carried out those who are
confident to do so. With the model at a safe height fly the model sideways, starting slowly and building up speed until it reaches its maximum
possible speed:
a)If the tail manages to hold its position then the blade length is OK.
b)If the tail starts to lag behind, then either more pitch is needed (if the mechanical limits haven't already been reached) or longer tail blades.
c) If the tail swings round suddenly and cannot return to the correct position then the tail rotor is stalling and longer tail blades are needed.
Maximising Performance for Advanced 3D/Aerobatic Flight - by Bob Johnston
To get the maximum performance from this or any piezo gyro it is essential to minimise the vibration reaching the gyro sensor. Apart from the
obvious balance checks, make sure that the canopy, fins, tuned pipe or muffler are not too loosely mounted, especially if the gyro is being used
with a fast servo, as it is possible for a resonance to build up which shows as a very fast shake, visible in the canopy and tail.
If you feel confident to do so, try slowly tumbling the model while checking for any visible vibration, a small amount is almost inevitable, but
try to dampen any large vibrations present. Alternatively tumble or roll the model at a safe height and if the gyro can be made to wag through
the manoeuvre this is a good indication that a component is resonating.
To set the maximum gain permissible for aerobatic flight, either a) fly the model as fast as possible in a straight line and twitch the rudder stick
a small amount: if this causes the gyro to wag, lower the gain and repeat the test until the tail cannot be made to wag anymore. Obviously if the
model cannot be made to wag initially, keep increasing the gain until it does, and then reduce the gain a few percent. Setting the gyro this way
should prove sufficient for all flying except in very windy turbulent conditions where the gain may have to be lowered by a few percent. b)
Alternatively, if you feel confident enough in your ability and your models reliability, put the model in a vertical dive for 3 or 4 hundred feet (90
to 120 metres) with the main rotor pitch at zero. Once terminal velocity has been reached, pull the model out in a smooth arc, and if the model
does not wag under these conditions it is unlikely to do so under any conditions.
WARNING: Only attempt to carry out these flight tests if you are 100% confident in your own flying ability, and the structural
integrity of your equipment.
Boom supports
Tests have shown that the use of boom supports significantly increase the rigidity of the tail boom and so allow a higher gyro gain to be used.
Generally the longer the boom supports the better they will work. Note: A loose/cracked boom support or a loose/cracked boom support clamp
can have a significant effect on the gyro gain. Even a slightly loose boom clamp or support will have a dramatic effect on the amount of gain
that can be used. Stand on the skids of the model and try to flex the end of the boom from side to side while holding a finger against the joint to
feel any movement.
Humidity
Under conditions of extremely high humidity it is possible for condensation to form on the piezo sensor. This can adversely affect gyro
performance. Where it is not possible to avoid subjecting the gyro to such humidity levels it is advisable to leave the model standing for a few
minutes with the radio switched on so that the internal heating of the gyro helps disperse the condensation. Always protect the gyro from ingress
of water (e.g. rain).
DOs and DON'Ts
DOs:
Do mount the gyro with its axis of rotation parallel to the helicopter main shaft.
Do mount the gyro on two of the supplied self-adhesive foam strips.
Do mount the gyro to a hard, smooth clean surface.
Do use the rudder ATV and rates to tailor required stick response.
Do check the sense of the gyro operation
before flight
.
Do use a battery state monitor and check it before each flight.
Do remove slop and stiffness from tail control linkage.
Do inspect tail gears etc. for wear.
Do explore the performance limits of this gyro with care.
DON'Ts:
Don't subject the gyro to mechanical shock.
Don't mount the gyro where it will be subjected to high vibration levels.
Don't use Pilot Authority Mixing.
Don't use Automatic Tail Stabilisation (ATS) or Throttle-Tail mixing.
Don't use unnecessarily long servo extension leads with the gyro.
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