RE: Airplane rudder gyro  
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All Forums >> Radios, Batteries, Clubhouse and more >> RC Radios, Transmitters, Receivers, Servos, gyros >> RE: Airplane rudder gyro
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RE: Airplane rudder gyro - 5/28/2008 3:48:36 AM   
Big_Bird



Posts: 3334
Joined: 12/18/2001
From: Arlington, TX, USA
Status: offline 		kahloq, I think heading hold and tail lock mean the same thing. Tail lock may be a heli term. If I have a cross wind I always takeoff my 1/3 scale Bucker Jungmeister in the heading hold mode. By the way you have to line it up on the runway just prior to takeoff and initialize the gyro in the heading hold mode. Just as the plane breaks ground you move a 3 position switch to the rate mode. In my case the switch center position is off.

Two different times I made a mistake on takeoff. Neither was serious. The first one was I put in a little rudder correction and the plane suddenly took off in a little different direction. On takeoff you must leave your fingers off the rudder. Trust the gyro. The second was when I broke ground and while climbing out started a turn to the left using aileron and elevator before switching to the rate mode. The rudder immediately said "no no we are not going to do that" and tried to yaw the plane back to the right. I immediately switched to rate and all was fine.

The gyro is installed in the plane in only one direction. It does not care what attitude the plane is since it only works on yaw. It has no idea where the horizon is unlike the autopilot systems. I have no experience with the JR gyro. It may be the answer to your prayers. All I know is that the GY401 has performed flawlessly for me. I think the only way we will know is to have someone install a gyro in a twin, fill one tank all the way and partially fill the other tank. Or talk to someone who has had the engine out experience on a twin with a gyro functioning. I never had an engine out (2 G-38s) on my B-25J but my plan was to hit the engine kill switch as soon as I realized that I had a failed engine and look for the best place to land.

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RE: Airplane rudder gyro - 5/28/2008 5:09:59 AM   
kahloq



Posts: 1892
Joined: 1/1/2006
From: Fort Collins, CO, USA
Status: offline 		Not going to argue this....ppl build twins with gyros all the time and use it to correct for an engine out. end of story. How its done...havent figured it out yet.

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RE: Airplane rudder gyro - 5/28/2008 3:03:52 PM   
BarracudaHockey



Posts: 10993
Joined: 7/13/2003
From: Orange Park, FL, USA
Status: offline 		Lets get some incorrect assumptions out of the way.

First, heading hold, heading lock, tail lock, AVCS (angular velocity control system) all mean the same thing.

Second, a gyro senses rotation about an axis and applies a correction signal to a servo. Thats it. They have no compass heading input nor do they align like full scale aircraft navigation systems. If you turned it on it's side it would correct pitch (elevator), turn it on its side and 90 degrees it will correct roll (aileron).

Infact we use 3 axis gyros for flybarless systems to give stability to a rotor system that the flybar does on a model helicopter. ( http://www.jaxrc.com/gallery/video_viewer.php?id=112 )

Now for the difference between heading hold and rate mode.

A rate mode gyro or a gyro running in rate mode will attempt to control the "rate" of unwanted movement about an axis. Lets use helicopters for example. If a heli was hovering in a sideways breeze a rate gyro would allow the tail to weathervane into the wind but a reasonable and controllable rate. The breeze would push the heli, the gyro would give a correction and recenter the servo when the rotation stopped and it would be at a new heading. This would repeat until the nose was into the wind and there was no more uncommanded heading change.

Same heli, same wind, but heading hold mode. The gyro will give a correction to stop the drift AND maintain that to keep its last known position. If the wind speeds up the gyro will apply more correction, if it slows down the gyro will apply less correction. If you give a stick command the heli will rotatate and the process will start all over again. If the helicopter is upside down, or falling sideways at full speed, it doesn't matter, the gyro only knows rotation about the yaw axis and will give the input needed to keep it there (up to the mechanical limits of the tail rotor).

So what is happening in your twin engine example? Nothing more than any other gyro application. The engine out is making the airplane want to yaw and the gyro corrects it. It doesn't try to establish a pre-determined heading, it just trys to keep it still.
.

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RE: Airplane rudder gyro - 5/28/2008 3:52:39 PM   
Big_Bird



Posts: 3334
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From: Arlington, TX, USA
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quote:

ORIGINAL: BarracudaHockey

So what is happening in your twin engine example? Nothing more than any other gyro application. The engine out is making the airplane want to yaw and the gyro corrects it. It doesn't try to establish a pre-determined heading, it just trys to keep it still.
.

In this example would the gyro be in the heading hold mode or the rate mode?

Thanks for dropping in with the information.

< Message edited by Big_Bird -- 5/28/2008 3:53:52 PM >

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Ken
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RE: Airplane rudder gyro - 5/28/2008 4:30:38 PM   
slopoke


 

Posts: 101
Joined: 3/1/2002
From: Madisonville, KY, USA
Status: offline 		Hey Guys, I have a nib Futaba CYA350 Gyro that I would sell. Too complicated for me.

Send me a PM if interested.

Poke

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RE: Airplane rudder gyro - 5/28/2008 4:35:19 PM   
BarracudaHockey



Posts: 10993
Joined: 7/13/2003
From: Orange Park, FL, USA
Status: offline
quote:

ORIGINAL: Big_Bird

quote:

ORIGINAL: BarracudaHockey

So what is happening in your twin engine example? Nothing more than any other gyro application. The engine out is making the airplane want to yaw and the gyro corrects it. It doesn't try to establish a pre-determined heading, it just trys to keep it still.
.

In this example would the gyro be in the heading hold mode or the rate mode?

Thanks for dropping in with the information.

Either way but in heading hold it will keep the correction in.

Flying an airplane around in heading hold is a funny proposition though. When you let go of the rudder stick the gyro will keep the plane it whatever attitude that it was in, we are really used to them self correcting to some degree. Its really strange. I did some experements with a gyro in my Funtana.

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RE: Airplane rudder gyro - 5/30/2008 1:57:27 AM   
kahloq



Posts: 1892
Joined: 1/1/2006
From: Fort Collins, CO, USA
Status: offline 		This is what was stated on the KMP B-25 thread regarding a gyro by eldher13:

"Regarding Gyros ...

Yes, this is exactly what a gyro in "rate" mode will do. You (and the heli gang) are correct that it will _not_ hold the correction. It will pulse to stop the yaw, which is exactly what you want. The point is that the gyro acts fast to the engine out. Of course, once the gyro corrects the yaw and releases the rudder, the plane will want to yaw strongly again! And the gyro will correct again. The plan is to keep the plane from entering a spin, not make it fly straight and true. Achieving this will require tuning the gain on the gyro in "rate" mode to get the desired affect.

So, when all is said and done, the gyro is buying you time to realize that the engine is out, so the pilot can provide the necessary control inputs for a controlled landing (hopefully on the runway). "

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RE: Airplane rudder gyro - 5/30/2008 4:30:15 AM   
Big_Bird



Posts: 3334
Joined: 12/18/2001
From: Arlington, TX, USA
Status: offline 		Seems like a good plan to me. Problem solved. Best of luck.

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RE: Airplane rudder gyro - 7/1/2008 1:16:34 AM   
don c



Posts: 18
Joined: 7/1/2002
From: Tulsa, OK, USA
Status: offline 		I just put a GWS piezio gyro in my Cox YMF Waco and I love it. Before it gave fits on the takeoff roll, especially with any crosswind. Since I put the gyro in the takeoffs are a lot easier. You still have to steer it, but it's a lot more predictable. You have to pay quite a bit to put a yaw damper in a Bonanza but we can get one for $38. I love this hobby. It's all about gadgets.

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RE: Airplane rudder gyro - 7/1/2008 1:32:06 AM   
Big_Bird



Posts: 3334
Joined: 12/18/2001
From: Arlington, TX, USA
Status: offline 		Don, that gadget on the right airplane can make flying a lot more fun.

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RE: Airplane rudder gyro - 8/2/2008 10:08:52 PM   
Big_Bird



Posts: 3334
Joined: 12/18/2001
From: Arlington, TX, USA
Status: offline
quote:

ORIGINAL: Big_Bird

The flight of the Bucker Jungmeister with the GY401 gyro this morning was an unqualified success. My transmitter settings were +70 (HH), 0 (gyro off) and -70 (rate). I used 2 of the advanced mixes with offset and channel 6 set to zero. The delay on the gyro was about 5%. The limit was set at 100%. Digital servo mode off.

Enough of the technical stuff, lets get to the fun part. Wind was calm. Initialized the gyro, started the engine and taxied out in Normal (rate). Took off in rate, sleight drift to the left, left my hand off the rudder. I did notice that when flying in rate, a little more rudder was required in coordinated turns. This was easy to get used to. Landed in rate. Did not touch rudder during roll out. Gradual turn to the right.

Taxied back out in rate. Wiggle centered rudder in HH mode. Took off and my old tendency took over and I think I bumped rudder during takeoff. There was a little deviation in heading direction but a good takeoff none the less. On two subsequent takeoffs in the Heading Hold mode I payed particular attention to not touch the rudder during takeoff. These takeoffs were absolutely arrow straight. Each time after gaining a little altitude I switched back to rate. For a little more perfect landing in rate mode a little rudder input is required but less than if the gyro is off. I did not do any takeoffs with the gyro off and hand off the rudder because I know what they are like.

One of the tests that I made was to climb at a 45 degree angle in the 3 modes. In the off mode the plane heading would start a pronounced turn to the left. In the rate mode the the left turn was far less pronounced. In the HH mode the left turn was non existent. I went through loops, Cuban 8, right side up spin (rudder and elevator only), inverted flat spin, and knife edge flight all in rate. All worked fine. I did not do these in HH mode. Since I am not a 3D flyer the HH mode will only be used for takeoff and will probably always be used there.

OK guys, I'm back and I have learned something about the GY401 that I had not realized before and was just lucky I guess. I learned this because one of our RCU members, flaviosi, asked me how set up the gyro with a 3 position switch on his 9C. I told him that I didn't have a 9C but I do have a new 10C and that I would get back to him.

Going back to my 8UAFS transmitter, channel 5 has only a 2 position switch and I wanted to use a 3 position switch (SW-C). I also used channel 6 (flap) for my output to the gyro sensitivity. Channel 6 knob must remain at 50% travel (centered). This equates to the gyro off position when the 3 position switch is centered.

I learned that I have been doing the rudder initialization wrong all of this time. I had been taxing the plane out, lining up on the runway and putting the switch in the AVCS mode (heading hold). I would then wiggle the rudder stick back and forth side to side 3 times ending up centered. I found out that if I did not return to center quickly enough then the rudder could have a small amount of offset. A few times I was puzzled that the takeoff was not dead true down the runway. Most of the time it was. The transmitter needs to be turned on first with the gyro switch in the AVCS position (up in my case) then the plane turned on. Put the switch in the normal or rate mode and taxi out to the runway and line it up. Do the rudder wiggle 3 times ending at neutral. Now switch back to AVCS. The rudder starts in neutral as it should. Apparently the gyro needs to learn the rudder left to right range while in the normal or rate mode and not the AVCS mode. Try this and let me know.

To keep things the same and since I still wanted to use the 50 MHz PPM receiver in my Jungmeister I took the FASST 2.4 module out of the 10C and plugged in the 50 MHz module. I changed the 10C to the PPM mode (very nice feature). I used 2 of the programmable mixes in the 10C. I set these up this way:
MIX3
RATE = +70%, MIX = OFF( this value will change with switch position), MASTER = OFST, SLAVE = CH6, LINK = OFF, SW = SwC, POSI = UP

MIX4
RATE = -70%, MIX = OFF, MASTER = OFST, SLAVE = CH6, LINK = OFF, SW = SwC, POSI = UP

The +/-70% is the sensitivity I use in the transmitter for AVCS/Normal.




< Message edited by Big_Bird -- 8/2/2008 11:44:05 PM >

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RE: Airplane rudder gyro - 8/2/2008 11:14:34 PM   
kahloq



Posts: 1892
Joined: 1/1/2006
From: Fort Collins, CO, USA
Status: offline 		Ken, my experience has been a little different regarding initializing the 401 gyro. In order for the gyro to function correctly on my plane, I have to have the switch(3 position switch on a JR 9303 2.4ghz radio) in the HH mode position when powering up the plane. If I do not, then it wont ever initialize for HH lock no matter if you put the switch in the HH position after powerup. It will simply blink the led light slowly in all 3 switch positions and the HH does not function at all, but rate mode does but slugglishly.
Now, if I power up the plane with the switch in HH mode, everything works just fine and it initializes quickly. I can then move the switch to off or rate mode and then back again to HH and it still works like its supposed to.
There are occasional instances when powering up the plane that the gyro pushes the rudder hard right and wont initialize at all. This is rare, but does happen, so I simply have to power down and then back on.

First pic shows the gyro under a blackened transparent plastic cover. The red LED light is easily seen and its steady on....HH mode. 2nd pic is just showing the gyro itself without the cover


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