DavidR

My Feedback: (1)

First off guys I am a jet pilot not a heli guy. (Don't shoot me!) Here is a problem that a lot of us are having. I am asking this here because I know you guys use gyros all the time.

JR 450, and JR 460T gyros mounted in a BVM Bobcat turbine plane. The setup uses two seperate servos thru a Y harness for the rudders. In my case today I have 2 JR 9411 digital servos, and a JR 450 gyro. My plane has around 75 flights with this setup. I run the gyro with very little gain in the gear up position, and around 50% with the gear down. Today with an ambient temerature of around 90 F at the start of the flight my gyro was fine, rudders were centered. During the course of the flight I noticed the airplane rolling slightly to the right, when I selected gear down (higher gyro gain) the airplane reallly wanted to roll right. I landed and as I was taxiing back into the pits I noticed both rudders deflected about 3/4" to the right. the gyro still worked fine and I could trim it out with the rudder trim. I turned the receiever off then back on and after trimming the rudders back I was fine. Gyro was centered and working fine. I could not get it to duplicate the scenario. I also noticed that before I reset it I could increase and decrease the gain and it would deflect the rudders more with increased gain. My second flight I reduced the gyro gain over all, and I still had the same problem, no problems early in the flight but about 1/2" deflection after landing. If this is a JR gyro probelm can you guys recommend a gyro I can use that
is NOT heading hold, but is adjustable in flight.


Also need to add that I am running a 5 cell pack with a 5.2 Volt voltage regulator.

Thanks in advance!

David Reid

DavidH

Don't know if it is a problem with your JR gyro or not. Sounds like you may have accidentally hit the rudder trim during flight. But here is the model numbers for two gyros made by Futaba for use in airplanes.
The GYA 350 for single servo use
The GYA 351 for dual servo use on the same axis.

David

DavidR

My Feedback: (1)

Nope did not hit the trim during flight. That would also not cause the shift of centering with the increase or decrease of the gain setting. Thanks.

Scotty740

Hi David,

Your problem could be related to temperature induced drift. A lot of the older gyros were temperature sensitive and would drift off center with a change in temperature. I used to see it when the heli would sit in the sun and the gyro would warm up. When starting to fly the rotor wash would cool the gyro back down some and induce some drift.

This has been solved with newer technology in the sensor elements and/or firmware for the gyros. The newer Futaba 401, 502, 601 and CSM 400, 540 though being heading hold can operate in normal mode and have pretty much solved this issue.

I'm not sure if this resolves the issue for you or if maybe you just have a gyro going bad. Let us know if you have any other problems or what you find.

DavidR

My Feedback: (1)

I swapped it out for a JR 900 that I had NIB and will fly it today. I talked to a buddy of mine that is Team JR guy he told me to turn it on and hold a hair dryer on it. If the gyro is good it should not change or should change very little. Well.... I tried it and after a few seconds the gyro gradually shifted to the left this time. Looks like it is going back to JR. I know of a couple of 460T's that have had the same problem.


What do you guys think about the CSM gyros? Is the 540 cpable of acting as a normal gyro not just a tail lock?

Thanks again.
David Reid

Scotty740

David,

I've got 6 helis with CSM540s in them. All work great and will work in normal mode with variable gain. A cheaper alternative is the CSM 400. Same gyro but without the external computer interface. The interface can be fitted by opening it up and soldering on leads and a plug. For you application though it would be just fine.