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Old 12-26-2011, 10:41 AM   #1
MattJenner
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Default Fly Bar Less on a 2 stage turbine

Hi All,
Seasons greetings,
I have been putting off going flybar less on my scale longranger, I was sent a video of the a Skookum on a Predator MW54, this poor guy has had over 3 crashed cos the unit seems be getting interference from ths high frequencies that a two stage gives out..

they seem to be ok on a single stage, as i have not hear any issues yet..
I was wondering, Lou,Chris, others who fly 3D are you using any FBL units on your MW44 or Mw54..

here is a video of a nasty incident where the pilot was just left helpless, this was the first flight after a prev crash and re build, I really felt sorry for the guy... 1m 25 is where it goes mad..


I have had a flight on small scale model that was FBL, it was ok in forward flight, but when you came into the hover it was horrible, it hated being kept still.. ( electric centry longranger)



I am interested in any comments, as I know some of you are using FBL units and I dont know much about them on machines that are using 2 stage turbines and running a low headspeed, around 1100/1280

Matt
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Old 12-26-2011, 10:54 AM   #2
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Ouch, that vids scares me. I am planning on a Vbarred Inteprid Turbine, powered by a Jetcat SPH5.

I never heard of any problems with the Vbar on turbine heli's, but with the Robbe units there where some issues in scale heli's powered by 2 stage turbines. Skookum also seems to have some non-programming related issues every once in a while.
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Old 12-26-2011, 11:08 AM   #3
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Yeah scary indeed.

fortunatly it went up before he cut the throttle, instead of coming right back at him.
It seems these units have been tested for electric and gasser nitro but not turbines..

And it reminds of when electrics first came on the scene, the ECS were putting out interference and crashing models, so the technology had to develope and improve..

The V bar I have seen but have not tried myself personally even though the version 5 has that scale setting on the PC

MAtt
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Old 12-26-2011, 11:11 AM   #4
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Which flybarless unit have you tested on the scale ship?
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Old 12-26-2011, 11:21 AM   #5
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i havent yet, purely cos of the horror stories i have heard.
John Tanner who does MHW magazine, his machine with a FBL unit was fine until he came in to land and it suddenly did a tic toc and went crazy... his longranger is the same as mine.

He crashed tail first, fortunatly not much damage, but he said it scared the hell out of him.. he put it down to a small vibration somewhere on the machine..

The only one that seems to be fine for scale is the VBar, but i have not tried it on a 2 stage turbine, nor has anyone else i know, they have only been fitted on the vario machines like the lama and EC120, which use a single stage Jako/Jetcat.. you are the first to post that uses a two stage..

I know Chris and Lou do a lot of flying in different configurations, hence the reaosn for my post and question on the freak site..

Matt
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Old 12-26-2011, 11:39 AM   #6
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I'm not using it yet, I'm waiting for some funds for the Inteprid turbine. I know the Bergen guys use Vbars, and I haven't heard any issues from them. They're not using a Jetcat though.

There's a lot of diffence in quality in flybarless units. Some are really simple, while others are very sophisticated. I think the cheaper onces should be avoided.
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Old 12-26-2011, 12:59 PM   #7
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Quote:
Originally Posted by Laurens View Post
Ouch, that vids scares me. I am planning on a Vbarred Inteprid Turbine, powered by a Jetcat SPH5.

I never heard of any problems with the Vbar on turbine heli's, but with the Robbe units there where some issues in scale heli's powered by 2 stage turbines. Skookum also seems to have some non-programming related issues every once in a while.
Hey Laurens.

As a recent Vbar convert on my Align machines I've been keeping up to date with what they are now offering and apparently there is a new sensor in the works that will be better on turbine machines, in this case less of a problem with turbines because of their high frequency vibration.
Also the Helicommand HC3-SX is meant to be ok on turbines now I think, or is going to be.

Might be worth you scouring the Mikado forum for the post on the new sensor in the works. I know the current Blue line sensor is less of a problem with vibes, but it still might not be perfect.
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Old 12-26-2011, 02:18 PM   #8
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Just watched the video and cringed, such a shame.

However any fbl model would suffer on the hard surface he was taking off from, combined with the very stiff Century carbon skids and it was a recipe for disaster.
He would have been much better with the model on the softer grass surface, might not have saved the model in this case, but would have limited the amount of fuselage vibes fed back into the air frame.

Also not mounting the sensor directly above the turbine on a metal platform would have been better to.
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Old 12-26-2011, 04:22 PM   #9
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At IRCHA, one of our customers had a bad incident with a V-Bar onboard, I do not know blue or black sensor, and am not 100% sure of the cause.

Heli was sitting in a pretty head high hover, then boom struck. The boom was recovered near the next flight station, about 100 ft away.

Now was this a Turbine problem or simply a V-Bar problem? I suspect that it was a single bad V-Bar, IIRC a bad solder connection was noted upon inspection of the device by someone with the knowledge to look at it. I think that the result would have been the same whether it was on an electric or a gasser.

Many guys have been running V-Bars and Skookums on our 44 Magnum's without issue, but that doesn't guarantee success on another helicopter with a Turbine engine.

Personally, I don't use any electronic stabilization on my FBL birds, Proper setup, proper blades, and simply flying the helicopter makes it possible. Once used to the flying characteristics, it's really not a big deal. But YMMV....
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Old 12-27-2011, 06:15 AM   #10
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I've been using the Futaba CGY750 on Trex844 Wren 44 heli for about 6 months now with no problems at all. In my area there is MA Spectra G conversion with a Wren 44 with a full size Vbar (blue) flying perfectly ok for around the same period.
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Old 12-27-2011, 08:13 AM   #11
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....
duplicated post DOH!!!
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Old 12-27-2011, 08:14 AM   #12
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Interesting comments and observations, thanks all for posting..

I agree if you can get away without stabalisation then all the better, the only thing i am unsure of though is how a 2 bladed non fly bar machine would fly, I have flown a 4 bladed head with no stabalisation but not a two bladed head..

Here is another video taken, this was on soft ground.. it is around 1min 35 to 1 min 50 where it goes funny.. this was the first incident..

I wonder if the MW44 doesnt suffer due to it spinning at such a high speed, and then you have the jetcat which is at a lower speed, the MW54 maybe just in that danger zone ? This is pure speculation on my part, but i owuld like to get to the bottom of why some of these do funny things on turbines..

Matt

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Old 12-27-2011, 11:22 AM   #13
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In that vid you can see some harmonics develop, the horizontal fin buzzes, then the tail kicks, then it goes batty.

For this helicopter, some things to try would be simply changing the rotor RPM, start a little slower for instance, getting the load on the rotors at an earlier RPM.

May also try different landing gear, something a little stiffer maybe, or possibly softer. The trick is to change the frequency of the helicopter harmonics.

As for your particular heli Matt, there really is no way to tell if yours will exhibit this phenomenon until you try it...
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Old 12-27-2011, 03:10 PM   #14
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As for your particular heli Matt, there really is no way to tell if yours will exhibit this phenomenon until you try it...

Thanks Chris, I agree, as the technology is still new, it is a case of suck it and see, hence the reason why I have built the Zealous 2 in pod and boom, as I really dont want to risk my Lovely Longranger which i have had so much fun flying this year.Won a couple of trophies in scale comps, not bad for first year of scale comp flying. The video below is a slow routine as it was blowing a right gale.

The Wrens really are top notch, totally reliable, have never looked back since turning Green.


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Old 12-27-2011, 03:39 PM   #15
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Four vbar'd helis here: Heli-Chris 700E 12S (just sold after 2+ years), 5-blade scale with MD500E body, Henseleit TDR 12S, and Bergen 44 Magnum with Wren 2-stage turbine. Perfection. Not a hiccup on any one of them; ever.

The Bergen turbine has had the vbar installed from the first rotation of the rotor without ever a twitch.
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Old 12-27-2011, 03:47 PM   #16
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Quote:
Originally Posted by MattJenner View Post
here is a video of a nasty incident where the pilot was just left helpless, this was the first flight after a prev crash and re build, I really felt sorry for the guy... 1m 25 is where it goes mad...
That wasn't a flybarless failure, I don't think. Looked like a collective servo malfunction. Full negative followed by full positive. That assumes the pilot didn't panic and actually and throw the collective stick forward.
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Old 12-27-2011, 03:54 PM   #17
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Quote:
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Here is another video taken, this was on soft ground.. it is around 1min 35 to 1 min 50 where it goes funny.. this was the first incident..
There's more going here than vibration issues. The swash stayed "cocked" even after the engine was shut down. All FBL units that I have observed (I am most familiar with the vbar), slowly return to level conditions once a commanded input is removed.
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Old 12-27-2011, 05:12 PM   #18
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it was not a servo failure,
the FBL unit put in a command, full negative then full positive.... in a split second, the pilot could only react by hitting cut..

Bell bloke re built this hellie, so it was mechanically perfect, before he passed it back to the owner.

I have seen others be operating lovely and well, then suddenly the unit puts in an unwanted command, causing not very nice affects.

Matt
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Old 12-27-2011, 05:13 PM   #19
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FBL units that I have observed (I am most familiar with the vbar), slowly return to level conditions once a commanded input is removed.

The beastex doesnt do that, you have to put in the oposite command, or it will remain at the last command like a HH gyro. so i have been told..
I flew one on a small centruy longranger funkey fuse, it was weird, cos i am used to taking my hand off the sticks on a circuit, but you cannot with the beastex, you have to put the oposite input, and fly it, like a HH gyro.

Out of the ones I have seen the V bar seems to be the best, but not tested on a low head speed two stage turbine..


Matt
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Old 12-27-2011, 05:24 PM   #20
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Quote:
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FBL units that I have observed (I am most familiar with the vbar), slowly return to level conditions once a commanded input is removed.

The beastex doesnt do that, you have to put in the oposite command, or it will remain at the last command like a HH gyro. so i have been told..
I flew one on a small centruy longranger funkey fuse, it was weird, cos i am used to taking my hand off the sticks on a circuit, but you cannot with the beastex, you have to put the oposite input, and fly it, like a HH gyro.
That's madness. That means that the swash could be setting there tilted during take-off. Yes, it's like heading hold on pitch and roll (the vbar flies as you indicate) but the vbar slowly returns to level with no input to prevent surprises during spool-up.
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