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airplane heading gyro question

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Old 12-18-2011, 02:47 PM
  #1
md11capt
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Default airplane heading gyro question

the following components/settings were used to install a heading gyro in a quarter-scale tailwheel aircraft: Futaba 6EX 2.4 GHz transmitter. Futaba R606FS receiver. Detrum GY48V gyro. Futaba analog servo. 4.8V nicad. JR JRPA004 on-off switch. Unused gear channel 5 used for gyro gain control. gear switch on transmitter used to select between heading hold and rate modes. heading hold will not be utilized, so its gain set to 3% to simulate the off position for the gyro. Rate mode will be used, and its gain set to 80%. The following problem exists: when system is powered up and heading hold is selected, system works as intended (no rudder movement when yaw introduced and servo remains quiet). Now when rate mode is selected and yaw is simulated, servo acts to counteract yaw as intended; however, the rudder servo has a constant low level chatter/jitter in idle mode (no yaw introduced). This chatter can be eliminated by taking the 80% gain down to about 30%, but this severely limits the rate mode function. Any ideas out there about what's causing this chatter at the 80% gain setting? Different quality servos have been tried, but all so far have just about the same chatter. Any wisdom greatly appreciated.
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Old 12-19-2011, 06:41 AM
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tevans55
 
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Default RE: airplane heading gyro question

md11-

I found this comment on a heli web site pertaining to the setup with a Futaba radio. Hope this helps. If not you might try a digital servo.




"I then adjusted the end points on channel 4 (tail) on the Futaba 7C transmitter to prevent over travel and jamming of servo. I had to set the servo type to digital servo -off (DS - off) to prevent servo buzzing."
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Old 12-19-2011, 08:33 AM
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Default RE: airplane heading gyro question

80 percent is a LOT of gain, start small and work your way up.

You dont set servo travel with the travel adjust on the radio, you set it by the limit pot on the gyro.
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Old 12-19-2011, 01:41 PM
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Default RE: airplane heading gyro question

The Detrum GY48V gyro is a clone of the Futaba 401 gyro. The 401 must be in heading hold mode when powered up to initialize. After it has initialized you can switch it to rate mode. Also 80% gain in rate mode is too high. I would start with 30% and work up from there.

Bruce
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Old 12-19-2011, 05:28 PM
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Default RE: airplane heading gyro question

If you try to fly in heading hold and you DON'T use the rudder. The rudder will deflect to try to turn the plane to the last heading before you stopped using the rudder. If you fly the rudder all the time then no problem.. As a ex heli pilot, I would recommend never to use the heading hold function in an airplane except to initialize the gyro.

To clarify my first statement.... (assuming you are flying in heading hold) If you take off due south, make a turn due east with out using the rudder. The gyro will think it should still be flying south and will deflect the rudder to make that change.

Hope this helps.

Ken
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Old 12-20-2011, 08:37 AM
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Default RE: airplane heading gyro question

agreed....
Imagine a helicopter sliding sideways..... your plane will attempt to do this too... Wings just don' work dat way!
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