Current users please note: Revision 4e is very similar to Revision 3. If you are using a small electric helicopter with a Revision 3 gyro, we do not recommend upgrading at this point. If you have been using a Revision 4 gyro in an IC model, and now wish to swap to an electric, please send your gyro back to CSM to have it reprogrammed to Revision 4e: cost £5 for the checkover and return insured postage. From now on, two separate versions of the gyro and gyro software will be available.

Micro SL420 manual

Optimising your revision 4e gyro

Stop equalisation technique

Stop equalisation is an aspect of gyro/tail rotor set-up that requires the most attention if optimum performance is to be obtained. The available tail rotor authority dominates stop times from fast pirouettes and most stop equalisation problems arise from a lack of tail-rotor authority one way,
usually in the leftward (anticlockwise) direction. This lack shows up in slower entry into left pirouettes and slower stops from right pirouettes. We find that good tail performance is obtained with 45 degrees of right tail pitch and 35 degrees of left tail pitch.

During the initial installation of the gyro you should make sure that the travel limits of the servo are set such that the pitch throw is limited only by the mechanical limits of the pitch linkage. Ideally aim for a servo arm length that gives throw limits between 90% and 120%. You can measure the required throw limits by temporarily connecting the tail servo directly to the receiver and adjusting the rudder ATV values until the mechanical limits are reached. (Remember to return the rudder ATVs to 100% after you have finished this check). We find it’s a common problem to have the tail servo arm too short; we rarely find one that’s too long.

During the initial flight carry out the Quick-trim procedure, adjust the gyro gain to the maximum that gives no wagging and assess the quality of the left and right stops from fast pirouettes (i.e. full stick). If there is a marked difference note which stop is the softer. After the flight, switch the gyro into Mode 0 (conventional, non-heading lock mode) and compare the left and right pitch throws at full stick from the hover pitch (stick centred). Generally, if you have noticed a difference in the fast pirouette stops there will be a corresponding imbalance in the left and right throws.

If the softer of the two stops is acceptable for your style of flying then it will be satisfactory to simply reduce the throw to soften the harder stop. To soften the stop from right hand pirouettes reduce the available left pitch and to soften the stops from left-hand pirouettes reduce the available right pitch. If you do this via the Quick-setup remember to repeat the Quick trim procedure on the following flight.

If on the other hand the softer stop is unacceptable you will need to increase the available tail thrust. Check if more pitch throw is available in the appropriate direction. If there is change the throw limit to make it available. If no more pitch is available the simplest way to increase the tail thrust is
by fitting longer tail blades. This increases the tail rotor disk area, the tail blade area, and the tip speed so a 10% increase in blade length will raise the available tail thrust by about 30%. Once the softer of the two stops is satisfactory the equalising the two stops can be done by adjustment of the
throw limits as described above.

Troubleshooting

The gyro will not enter the Quick-Setup routine

The gain is probably too low - increase the gain for both modes to 100% for now, and return them to the desired setting later. Remember also to turn off ATS (revo) mixing.

The model pirouettes violently as soon as it starts to lift off

The gyro sense has been set incorrectly. Check that the servo operating sense has been set correctly - when you put in a left turn command, the leading (fatter) edges of the tail rotor blades should point right. If this is not happening, change the servo reversing of the tail rotor channel in your transmitter. Then repeat Quick Setup to set the gyro sense correctly.

The tail wags from side to side in the hover

Reduce the gyro gain, using the ATV/travel adjust on your gain channel

The model flies fine in one gyro mode but wags in the other

You have too much gain in just the one mode. Reduce the gain on the mode that wags.

The tail response is not crisp enough

Increase the gyro gain. It is best to increase it gradually, until you see the tail start to wag, and then reduce it again until the wag stops.

The model wags even when the gain is very low

The problem is probably with the linkage - check that the linkage is not suffering from slop or friction, and that the tail hub bearings do not lock up under load. You should also check your servo. A slow servo or a very short servo arm may also cause this problem.

In mode 1, the model slowly rotates

Carry out the Quick Setup again, so that the gyro can sample an accurate stick centre value. Remember to keep the stick trims centred, and not to touch the sticks or the model during the power up time.

The model hovers well in mode 1, but rotates in mode 0

Repeat the Quick Trim procedure.

Even in calm conditions, the model suffers continuous small movements of the tail. It sometimes appears to drift.

The problem is most likely to be caused by vibration. Check that the wires leading to the gyro are properly supported - a long stretch of flapping wire may cause the gyro to move too much, and an over-tight anchorage may prevent the anti-vibration mount from working correctly.

The model flies fine on the first flight, but after a while the tail starts to wag

Fast gyro and servo combinations can run down the battery. Cycle the receiver battery and check its performance. You should consider using a fast Delta-peak charger to top up the battery between flights.

The model was fine last season, but now the tail wags

Check that the tail control linkage moves freely, paying especial attention to the pitch slider and the tail hub bearings. The receiver battery may have developed a high internal resistance - cycle the battery and check the capacity. The capacity may seem normal at low discharge rates but drop suddenly at say 3 amps.

The left and right hand stops are not equal. On one side the stops are slow and on the other they are bouncy.

Carry out Quick Trim, and make adjustments to the linkage if necessary (see the manual for details). See the Stop Equalisation section above.

I am running a high gyro gain, but the stops from high-speed pirouettes are still too slow.

The maximum available tail thrust is too low. The best ways of increasing the tail authority are: increase the pitch range of the tail; change the tail gear ratio to increase the tail rotor rpm (only possible on some machines); increase the length of the tail blades. Caution: when increasing the tail blade lengths, check that there is still sufficient clearance between the tail blades and main blades. If you cannot increase the tail blade length, then increase the chord of the tail blades.

The model twitches erratically and violently in yaw.

If you are using a belt-driven tail, then the problem is probably static electricity. If this problem is not sorted, then it may cause damage to the electronics on your helicopter. An anti-static spray on the belt is the easiest solution. It is also possible to get grounding systems which ground the electricity safely.

If you are still having problems, or would like any advice about improving the performance of your gyro and helicopter, please contact us:

email: tech@csm-ltd.co.uk
tel: 01457 854680 within Britain and 44 1457 854680 outside.