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RE: Airplane rudder gyro - 8/25/2007 3:10:26 AM   
Big_Bird



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quote:

ORIGINAL: Flyfast1

Ken,

I did try a servo and confirmed the settings. I just tried wiggling the rudder after returning to AVCS mode and this does reset the gyro so it works correctly. I currently have the AVCS side set to 90% and the rate side set to 30% and that seems fine. This amount of gain in rate mode seems completely benign.

I am very interested to hear how this works out for you this weekend. That DC 3 is a sweet plane. It looks like the rudder is not in line with the engines, so there must not be much air moving over the vertical fin and rudder during the initial takeoff roll.

By the way, I also played around with the gyro more in rate mode and I can see why it doesn't provide much damping for our application. It seems to dampen jerky motions the most and when my ME109G turns left after the tail lifts it is not jerky, but a smooth, strong turn. It's a large airplane and at 37lbs, kind of lumbers down the runway a while before it gets exciting. Some have suggested "getting the tail flying quickly" by applying a lot of power during the initial takeoff roll, but this has not turned out well for me. It seems to just make things worse and a slow application of power seems to work best. But I digress.

Good luck this weekend!

-Ed B.

Ed, it looks like for some reason you need a minimum setting like 30% on the Normal mode for the gyro to act correctly in the AVCS mode. I see no problem with this. It really sounds as if you need to try your ME-109G in the AVCS mode. If I were testing your plane in AVCS mode I would ease on the throttle and come up to about 20 or 25% (somewhat less than lift off speed - fast taxi) on the throttle and watch it respond then drop back to idle. Taxi back in Normal mode and do it again, maybe a little faster this time. Taxi back in Normal mode. If all looked good I would switch back to AVCS and make a normal takeoff taking care not to touch the rudder. I really don't believe it is necessary to instantly switch back to Normal the moment you break ground, just after the plane attains some altitude and before the first turn. That is the way I plan to fly the Jungmeister on it's first AVCS run.

I'll bet that ME-109G is a lot of fun. We go down to Bomber Field in Monaville Texas every September for the B-17 gathering and Big Bird flyin. That is a true Mecca for warbirds. There are usually several Me-109s, FW-190s and Stukas. I lost my Ziroli Corsair down there last year due to radio failure. Here are a few photos.

Thanks, we'll let you guys know the results of the testing.

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< Message edited by Big_Bird -- 8/25/2007 3:13:00 AM >

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RE: Airplane rudder gyro - 8/25/2007 1:33:47 PM   
BarracudaHockey



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From: Orange Park, FL, USA
Status: offline 		90 percent using end points is really 80 percent gain.

Also beware not to touch the rudder trim after the gyro is initialized or it will think you are telling it to turn.

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RE: Airplane rudder gyro - 8/25/2007 1:41:15 PM   
Big_Bird



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Status: offline 		"Also beware not to touch the rudder trim after the gyro is initialized or it will think you are telling it to turn. "

Good point.

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RE: Airplane rudder gyro - 8/25/2007 2:33:20 PM   
BarracudaHockey



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Status: offline 		Ken those planes are geourgous btw!

Here's my Corsair

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RE: Airplane rudder gyro - 8/25/2007 8:38:19 PM   
Big_Bird



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Status: offline 		We are back from the field and the tests went great. The gyro acts exactly like I thought it would. There were no surprises. My friend used his other small Mustang with the gyro mounted on the side of the fuselage instead of the twin Mustang. See photos

The first takeoff was made in Normal with the Normal mode set to 80% and the AVCS mode set to 10%. The plane did a pretty good rudder hands off takeoff but still drifted a little to the left. We had a 5 mph westerly cross wind and we were taking off to the south. A great combo for this type of testing.

The second and third takeoff attempts were made without the gyro in operation (switch in the center position on his 9Z transmitter). In both cases the throttle was shoved hard and the plane did a hard left hook with no manual rudder input. I think he aborted one takeoff and horsed the other one into the air.

He then made a takeoff with AVCS on at 10%. Again the rudder was not touched. The takeoff was fairly straight. The switch was put in Normal after liftoff. After landing I asked him to set the AVCS for 70% and the Normal for 50%. I then made a takeoff in AVCS. Even with the 5 mph cross wind and less than a smooth runway the plane took off arrow straight, as near perfect as you could want. After I landed he took off again in AVCS with the exact same results.

During all of these flights AVCS ,Normal, and off were switched in and out while we observed the resulting reaction. If you are not flying the gyro for 3D aerobatics then I don't think you would want to use it in AVCS other than for takeoff. Takeoff is where AVCS is really worth the money. Of course, during takeoff with AVCS, we didn't touch the rudder and made sure to give the rudder a wiggle and back to neutral before coming up on throttle. In the air when using AVCS, if the rudder were touched the plane would develop a continuous turn in the direction that the rudder had been pushed. To correct this the rudder would have to be moved side to side and back to neutral. Just for normal flying with loops or rolls this is a nuisance. Flying in 50% Normal (rate) is very comfortable and not even noticeable. In fact I couldn't notice any difference between flying in gyro off or Normal.

At no time did we get a scare while using AVCS. So many times I have read DO NOT USE AVCS DURING TAKEOFF. This was obviously written by someone who has never tried AVCS for takeoff, is simply parroting what they read, has a broken gyro, or it is a CYA action. Regardless, they had me fearful but I'm now a true convert after what I saw and experienced today.

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RE: Airplane rudder gyro - 8/25/2007 10:20:42 PM   
BarracudaHockey



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Status: offline 		Good stuff, thanks!

I think the real keys are, center the rudder and keep your mits off it during the takeoff sequence.

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RE: Airplane rudder gyro - 8/25/2007 10:40:52 PM   
hlhamner


 

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From: Flower Mound, TX, USA
Status: offline 		Big Bird,

Just got back from flying my Twist 40 (GY401 gyro installed) and Showtime 90 (G500A JR rate gyro installed) and I tried the Heading hold mode on the GY401 for take offs and I had similar results. First take off was into about an 8-10 mph wind with throttle slowly and cautiously being fed in until take off. The take off was straight with no surprises. I am running about 80% gain in AVCS (HH) mode. Then, the next takeoff was into a direct cross wind in HH mode and I was ready with the ailerons and the gyro switch. I punched full throttle and again, take off with a direct cross wind was very straight with no surprises. I love taking off with this gyro.

Okay, now for the fun stuff and the real reason I installed the GY401 gyro. Flying about 20 ft above ground in my Twist 40 I switched to 3D rates and then switched from normal gyro mode to heading hold mode and pulled up into a Wall. Apply some power and the little, short moment, Twist, hovered like it was being help by an invisible string from above. The wind was blowing so it looked pretty cool to see it hover 30 ft above ground moving across the field. Torque rolls are now much easier - just need to keep the elevator movements straight and hold some left aileron to help the torque. Again, I love the GY401 for airplanes. I wish I had done this sooner.

I highly recommend the GY401 gyro for use in airplane takeoffs if needed and especially if you are into 3D. I didn't have time to try it but I'll bet this will make waterfalls much easier if the stall is entered in heading hold mode.

The only disadvantage I see so far in using the GY401 gyro is that your dual or triple rates don't work on the gyro channel which, in my case, is the rudder. Everything, even in normal mode, is at the high rate so I used lots of expo, like 75%, on the lo rate switch side. Unless I find the answer for this I would not use the gyro if you have rudder mixed with ailerons to get a coordinated turn on a larger or scale model. It just may give you the opposite of what you expect.

Do you know how to totally disable the GY401 in flight so the dual rates will work as you would expect?


Hank

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RE: Airplane rudder gyro - 8/26/2007 12:17:28 AM   
Big_Bird



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Status: offline 		Hank, congratulations on your test today. I have spent a lot of hours combing 4 RC related web sites for answers to "Airplane rudder gyro" questions only to find untruths, half truths, stupid answers and insults. I am hoping that the ground work that we have done here will help some fellow modelers who someday search for the same thing.

As far as how to turn the gyro completely off with a 2 position switch on a Futaba 7 channel radio, I'm not sure. I know my buddy can do it on his 9Z and I may be able to do it on my 8UAPS transmitter because I do have a 3 position switch that I can use. I'll work on that tonight.

Ed, it's now time for you to try the ME-109G on AVCS

Hey cuda, nice Corsair

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RE: Airplane rudder gyro - 8/26/2007 5:59:43 PM   
Big_Bird



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From: Arlington, TX, USA
Status: offline 		"The only disadvantage I see so far in using the GY401 gyro is that your dual or triple rates don't work on the gyro channel which, in my case, is the rudder. Everything, even in normal mode, is at the high rate so I used lots of expo, like 75%, on the lo rate switch side. Unless I find the answer for this I would not use the gyro if you have rudder mixed with ailerons to get a coordinated turn on a larger or scale model. It just may give you the opposite of what you expect.

Do you know how to totally disable the GY401 in flight so the dual rates will work as you would expect?"

Hank, Maybe I am misunderstanding what you are saying. I drug out my retired Futaba FP-T7UAF transmitter and put a charge on it. I set the dual rate for the rudder channel 4 at 100% and 50%. I wanted to see if the dual rate on channel 4 had anything to do with the operation of the gyro control channel 5. As I suspected, it did not. Channel 4 and 5 are completely separate independent channel and do not effect each other. Even in a situation where the rudder is a mixed slave to the aileron the rudder will receive a normal signal through the gyro. All of this mixed operation should be in the Normal mode and not in the HH mode. At this point I don't see why the dual rate switch on your rudder would not work as it always has.

By the way, with mixing, I can use switch C, a 3 way switch, for AVCS-off-Normal on my 8UAP and 8UAPS transmitters. I don't see any way to do that on your 7UAF

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RE: Airplane rudder gyro - 8/26/2007 7:01:21 PM   
Flyfast1


 

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Status: offline 		Ken and Hank,

I want to thank you both for the work you have done here and the others who have contributed, such as Barracuda. During my searches on the Internet I had found the same warnings as Ken to never use the heading hold mode with an airplane but never found explanations for the warnings. Just conclusory statements that it should never be done. I am glad that those participating in this thread took the time to understand how gyros work and that they can in fact be used safely and effectively in airplanes. Having that P51 as a test bed was perfect. After your experiments and the flight tests by Hank, I feel confident that this is going to work out fine.

"Ed, it's now time for you to try the ME-109G on AVCS" LOL! Yes, I am ready now and will be able to test it next weekend, since it is a long Holiday weekend. Just so you understand my hesitation, I fly off a narrow paved strip with very little room on the sides. On the near side of the runway is a protective barrier that does a good job of protecting pilots from any planes that stray towards the pilot stations, but it will tear up an airplane. Off the far side of the runway is a small grass area that is riddled with gopher and squirrel holes and just beyond that is a barb wire fence that will fillet a plane like a Mackeral. So, takeoffs and landings have to be on the runway.

With the experiments you have run, I feel confident to try this with my ME109G. I am thinking for the first flight that after I taxi and line up with the center line, I will walk out behind the plane to make sure the plane and rudder are aligned with the centerline. I like the idea of setting up the gyro on a three position switch (AVCS mode; off; rate mode) and will program this today on my 9C.

Thanks again,

Ed B.

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RE: Airplane rudder gyro - 8/26/2007 7:43:55 PM   
Big_Bird



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Status: offline 		Ed, I think if you were to buy a GY401 and stick it into a plane and only briefly read the instructions then you could get in trouble with AVCS. It is definitely not Plug n Play. If you thoroughly research the characteristics of the gyro and know how to operate it and understand all of the doos and donts then it can be a terrifically good enhancement for your plane. I doubt that it knows that it is in a helicopter or a big ME109G.

Here is a photo of my friends Weddell Williams racer with a G-62 in the nose. It is a super looking and flying plane. Due to the narrow gear it is a great candidate for a 401. Some of the takeoffs can be a bit hairy to say the least. He said he may put one in it also.

I really understand about the confined runways. Most of the fields where I fly are not as confined as yours. Best of luck on your AVCS test next weekend. Let us know how it comes out.



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RE: Airplane rudder gyro - 8/27/2007 4:30:46 AM   
Flyfast1


 

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Status: offline 		I have test results to report sooner than I expected. Encouraged by the reports here and a favorable wind direction, I headed out to the field with a flying buddy. Per the excellent suggestions provided by Ken, I did four taxi tests. The wind was a stiff 17mph, but generally down the runway, sometimes quartering from the left. On each test I taxied out to the runway in rate mode, lined the plane up with the center line and changed to AVCS (HH) mode and reinitialized the position by moving the rudder back and forth. The first few times I did this I walked out to the plane and stood behind it to ensure that the rudder was initialized straight and that the plane was dead center with the center line. On the first run I very gently added throttle and allowed the plane to slowly gain speed, but not to the point of the tail lifting off. The wind was blowing slightly right, causing the plane to weathervane left and I could see the gyro putting in some right rudder to correct. After reducing throttle and letting the plane slow, I switched back to rate mode and taxied back to the starting point. On the second run, I took the plane a little faster, but still not lifting the tail. Same result. On the third run, I went faster and lifted the tail. We could observe the gyro putting in a sigificant amount of right rudder almost immediately to keep the plane lined up on the center line of the runway. AT one point it even put back in a little left rudder to re-correct. So the gyro was working hard and doing a good job of keeping the plane on the center line of the runway. On the four attempt, I went faster still and took the plane off. The result was a very straight takeoff run and climbout, one of the straightest ones I did, and I didn't touch the rudder. I climbed the plane straight out and raised the gear and switch the gyro from AVCS to rate mode, then flew it normal.

So, the 401 gyro in AVCS (HH) mode was able to tame a really squirley 109G. This plane is by far the trickiest plane I have ever had to takeff, and the gyro turned out to be a very important tool in taming this beast. It takes a lot of mental control to resist the temptation to touch the rudder. It was easier during the first few runs because I knew I was going to shutdown the attempt.

Thanks to all the contributions from others. I am glad to answer any questions that others have.

-Ed B.

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RE: Airplane rudder gyro - 8/27/2007 2:42:26 PM   
Big_Bird



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Status: offline 		Well there you go Ed. Another unqualified success story. I think the taxi runs are certainly a confidence builder. I hope my 401 comes today.

Do you have the gyro on a 3 position switch so that center is off? What is your AVCS and Normal setting on your transmitter? When flying on Normal, did you notice any difference than before you put the gyro in the plane? What do you have the two pots, delay and limit, on the gyro set on?

I know it's a long trip but if you can ever make it to Bomber Field you and your ME109G will be in good company. This year it is September 14 - 16. We (3 of us from Arlington) always go down Wednesday morning before the meet starts and it will getting crowded at that time. As usual there will be about 200 pilots and 350 planes of which about 70% will be warbirds. I'll be taking the 1/3 scale Jungmeister, 1/3 scale Super Decathlon, and 114" WS PT-19. This year Mack Hodges is supposed to be there with his highly aerobatic B-29 powered by 4 ZDZ80RVs. It's almost unbelievable what he does with that huge airplane. So far I have only seen his performance on DVD. Of course, BB Webber (owner of Bomber Field) will be flying his big Russian Bear Bomber. There will probably be up to 10 10ft WS B-17s. What a GREAT flyin.

< Message edited by Big_Bird -- 8/27/2007 2:54:46 PM >

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