Flyfast1
Posts: 395
Joined: 9/25/2005
From: Livermore, CA, USA
Status: offline
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Hello,
I am currently experimenting with a Futaba 401 gyro in a 1/4 scale ME 109G (102"  with a Quadra 75cc engine and am very interested in the experiences of others using this gyro in fixed wing aircraft. Before people ask, yes, I know how to use the rudder and always fly coordinated turns. But, this airplane has notoriously difficult ground handling because of the narrow landing gear which are in a V configuration. When the tail first lifts off the ground, this plane has very little rudder authority because of the small size of the vertical fin and rudder and it can turn hard to the left, especially when there is a crosswind coming from the left of the aircraft. It is extremely difficult to time exactly when to add right rudder and if it is not done immediately, the plane turns left and it is very difficult to bring it back right with rudder.
Within the last few weeks I installed a 401 gyro and a Futaba 9252 digital servo on the rudder and tail wheel. I have so far used it only in normal mode and have it coupled to a switch on my transmitter so that in one position the gyro operates in normal mode and in the other position the gyro is disabled. On the ground when I pick up the tail and move it quickly to the right, to simulate the P factor causing the plane to yaw left, the gyro briefly adds in right rudder and then the rudder returns to neutral (assuming I am not touching the rudder stick). My experience so far has been that using the gyro in normal mode has not really helped. When operating in normal mode, the gyro will only briefly move the rudder to the right in response to a left yaw. In actual flights, the right rudder correction performed by the gyro when operating in normal mode has not been enough to hold the plane on a relatively straight line and I don't think has helped me to put in right rudder myself by giving me a "head start". The right rudder added by the gyro is just not enough in normal mode. The gyro adds in right rudder very quickly, but neutralizes the rudder just as fast. I have adjusted the rudder travel on the gyro so that I am getting full rudder deflection and also increased the gain to about 80%. I have turned on the digital servo switch and set the delay to 0.
So, that brings me to where I am now, which is to try the AVCS (or heading hold) mode. I am optimistic based upon my ground experiments, but also have some reservations. I'll start by saying that I will use a switch on the transmitter to enable and disable the gyro. I think being able to disable the gyro from AVCS mode is prudent from what I've read. I believe the recommendation from Futaba is to use a switch to change between AVCS and normal modes, but to adjust the gain in the normal mode to be very low, say a few percent, so that it is effectively a disable mode. In AVCS mode when the plane is on the ground and I lift the tail and move it right (nose going left), the gyro will correct with right rudder. But, unlike the normal mode, the gyro will hold right rudder until the tail is moved left back to the starting position. As the tail is returned to the starting position, the gyro neutralizes the rudder. This seems to be the desired behavior to assist with straight line take offs. But, here is the strange part. After picking up the tail of the plane and moving it right, the gyro will move the rudder right to correct. Now add in some right rudder using the transmitter stick, to simulate a take off run. This creates some sort of an offset in the rudder and after the gyro has corrected the heading the rudder is no longer at neutral, but still has some right rudder deflection. You have to manually move the stick back to the left to take out the right rudder offset. Try it and you will see what I am talking about. I am trying to envision how this would work in actual practice. Would this mean that after rotation I will still have right rudder applied until I correct it manually? Perhaps the solution is to not use any manual rudder and let the gyro handle it? From what I can tell, the gyro is very fast and in AVCS mode will hold right rudder until the plane heading is corrected to the starting heading That sounds okay, but may be hard to do, given my natural reaction to use a lot of right rudder with warbirds. Thoughts?
-Ed B.
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RE: Airplane rudder gyro - 
