RE: How does a Gyro work on Rudder Application?
Kram,
I am soooo humbled in your presence and cannot add much to your answer.
Here is the original story as part of an on going series I wrote for rcwarbirds.com
GYRO”S on AIRPLANES!
Rudder Control.
Having trouble with a short fuselage Tail dragger? (Cub, Biplane, Ultimate, Cap, etc.) Does it ground loop during takeoff? Landing? Unexpectedly turn on takeoff, landing, or hovering? Learn to use the left hand—the rudder!
OK you never listened to warnings on “Don’t DO Twins” why listen now! Don’t despair! Help is now available, and A. its cheap, B. easy to install, C. it works! The new piezo electronic gyro’s are here. They can be used to stabilize the rudder. And just about every mfg has some, Hobbico, Futaba, JR, and Expert to name a few. I am not talking about “heading lock gyro’s”, those are for the helicopter guys.
Installation is fairly straight forward.
1. The gyro is installed in series between the receiver and the rudder servo.
2. The rudder is centered using the center adjustment on the gyro and/or control linkage. Start with the transmitter trim tabs centered also. The Hobbico Multipurpose gyro must be set up with both; the mechanical center of the servo arm at 50% gain, after it is installed in series with the gyro, or it will only work one way. Use the gyro gain setting first and then the radio if needed or applicable.
3. Make sure to set the “Gain” on the gyro sensitivity to about 50% for initial testing.
4. Check the gyro orientation in the plane for proper action. Mount the gyro in such a way that it will not turn or come loose in flight. (If this were to happen things will get real interesting, real fast.) The proper location is at or very near the C.G., and away from heat and vibration!
5. Turn everything on and check operation. Proper operation can be checked by moving the tail horizontally to the right and observing the rudder movement. The rudder should quickly move to the right also, trying to push the tail back to the left. Its actually trying to re-center the fuselage. If the rudder goes left as you push the fuselage to the right, DO NOT FLY, the action is reversed and will need to be corrected by either using the reverse switch ON THE GYRO, or physically turning the gyro around 180 degrees.
That’s all there is to it GO FLY!
Flight Characteristics
1. Expect to take off in an unusually straight line. In most instances rapid throttle advance will only require minor rudder control or none at all.
2. In flight you must use the rudder with the ailerons to turn. If you try to turn, using only the ailerons, the rudder gyro will fight the turn and cause the plane to try and fly sideways. Using the rudder will override the gyro to allow the turn. When the rudder stick is released the gyro goes back into action to stabilize the plane.
3. Unless you can turn the gyro off, using another channel, do not perform rolls or tumbling maneuvers! The gyro will fight the controls and cause a simple aileron roll to become a barrel roll. This can be very scary! Check before you buy the gyro to see if this feature is available. The Hobbico Aero Gyro or Expert does, the Multipurpose gyro does not.
4. Landing will be the easiest experience ever. Come around, line up on the runway, use elevator and throttle to land and roll out straight. This can be done even in a moderate crosswind.
5. If, during flight, the fuselage wags back and forth, the gain is set to high. Land and reduce the gain on the gyro. If the gyro does not seem to keep the plane tracking straight, increase the gain.
6. Nose high hovering, or hanging on the prop, will become much easier. You will still have to use the ailerons and rudder to control the plane, but it will be much easier to accomplish.
7. Loops will now be straighter and cleaner.
Some additional information and reminders concerning gyros. I have been using the Hobbico line and am well satisfied with the results. The Multipurpose gyro is the straight forward, on all the time, and cheapest thing going. Priced at between $65—$75, it is very effective in trainers, cubs, Telemaster, and generally any plane that you do not plan on doing a lot of aerobatic maneuvers. The next step up is the Expert Gyro, and others. Priced at between $85- $100 it can be turned on and off via another channel. The sensitivity of the gyro can also be adjusted up and down as needed, in flight. This gyro is ideally suited for applications where the ability to turn it off during aerobatic flying is required. I have found that it may not satisfy all applications due to not enought gain. Finally, if you have two aileron servos mixed via separate channels, use the Hobbico “Aero Gyro” (Or similar). It has dual inlets, outlets, and gain control. Priced at $100-$120 this gyro can be used for aileron stabilization (to be covered in future articles).
Since the actual current draw on a gyro is very low one would think that no additional increase in the battery pack is necessary. This is not the case. Although the draw from the gyro is low the control surface that it is controlling is moving about ten times more than normal, due to the constant corrections being made by the gyro. With this in mind a larger battery pack would be a good idea. The only way around this would be to reduce the number of flights and keep a regular check on the condition of the flight pack, or use of a field charger between flights. Some of the non piezo type gyros allow the use of a separate battery pack for the gyro only. Futaba makes one and I’m sure others do also. Do your homework before you buy and do not assume anything. Talk to people that use them to get an idea of what you need. While we are on the subject of battery packs, servo reaction speed is critical for getting the maximum benefit from the gyro. With this in mind going from a 4.8 volt system to a 6.0 volt one will increase the torque output and speed by almost 20%. If you wish to stay with the 4.8 volt packs then you might want to consider the high speed servos for those control surfaces that the gyro controls. Pull - Pull systems or at the very least a stiffer single rod is recommended as the control surface is now much more useful and demanding of precise movement. Make sure there are NO Z BENDS in the control rods where they exit the fuselage. If your control rods bend the effectiveness of the gyro will be significantly reduced. Setting the control surface service throws higher will also help gyro effectiveness.
Personally speaking gyros will do everything noted above. This in effect reduces the demands placed on your skills. Use of gyro’s is actually banned in some competitions. It will also reduce the development of those same skills. They should be used as enhancers rather than crutches to your ability. Remember not every plane has or needs them.
Hope this helps,
Twinman