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Concept 30 did the chicken dance!

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Old 08-18-2002, 09:41 PM
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Default Concept 30 did the chicken dance!

Well I had my first major crash today with my Concept 30 SR.

I've been hovering for about a month with a LMH Corona, and lately the Concept 30. Today I finally got some courage built up and threw it into foward flight. She flew just like an airplane at that point, and since I also fly planks, I was having a ball.

Made three beautiful circuits around the field, and was grinning ear to ear. I came around the far end of the field, and something mechanical happened.

My best guess is that one of the pitch linkages came loose. The engine sagged horribly all of a sudden, and after a few seconds a wild vibration crept in (vibrated the training gear off the chopper). It vibrated like this for another few seconds (probably wasn't that long, but my sense of time was skewed), and it seemed the blades just lost all their momentum. At that point the tail started spinning, and I just quit fighting it, and yelled to everyone to look out.

In the post-mortum inspection, I noticed one of the pitch linkages was nowhere to be found. At first I thought maybe the engine had sagged and let the headspeed drop, but after thinking about it that didn't explain the wild vibrations I was getting. This is why I think the linkage came off in-flight rather than during the impact. If my deductions are right, this would have caused the engine to sag, and would also account for the vibrations and the loss of headspeed towards the end. Anyone ever had a similar experience?

It hit pretty hard, but did much less damage than I thought it would. Total damage: 1 tail boom, 1 set of blades, 1 flybar, 1 canopy. I already had a set of blades, so it is all on it's way from Tower now for under $100.

Either way, I'm still tickled with the flights today. I got over the FFF hurdle, and can't wait to get it back in the air to burn a few more circuits. I guess I'll just have to practice in the front yard w/ the Corona until next weekend.
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Old 08-19-2002, 02:19 AM
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Old 08-19-2002, 02:44 AM
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Default Concept 30 did the chicken dance!

What was the heli attitude when all this happened (straight/level, etc.). I had a flybar set-screw come loose and very similar symptoms. I actually got it on the ground before the tail boom came out of the frame from the vibration. I had no idea what happened until I saw the pitch sliders all the way out (didn't think that should happen).
I had just taken off after putting a new motor in my bird so I was being a little cautious and keeping it close the the ground and only mild FF.

So you think the collective came off? I would have thought you would have lost pitch if that had happened (EG heli=rock).

To bad you wrecked it. Any gory photos?

Good luck and keep at it.

THX-
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Old 08-19-2002, 03:52 AM
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Default Concept 30 did the chicken dance!

I don't know for sure the collective came off, but it is my best guess. But now you have me wondering ....

The heli was flying for a while (or it seemed like a while) after the failure, and before it hit the ground. I'll try to relive how it felt in the air.

I brought it around the last turn, and added a little throttle / collective as well as up elevator to keep my altitude and attitude correct. At that moment, I heard the engine sagging horribly, and the heli twitched hard to the left (my right). I managed to snag it and bring the tail back in line, but it seemed I had lost a lot of power. I had to hammer down on the collective to keep it going, and I thought I may be doing my first unplanned auto at that moment.

It did settle back into a hover briefly, however, at around 10 - 15 ft. altitude. This is when I noticed the vibrations and the heli really looked like it was going to shake itself apart. I'm not sure what the engine was doing at this point, as I was focused TOTALLY on trying to set this thing down gently.

I got it to drop 5 feet or so while under control, but then the tail just started going round and round. The heli dove off to my left (towards the trees), and began banking towards the ground. At that point I realized I couldn't do anything with it and yelled a heads up. No one was anywhere near it, but I just wanted to make sure.

So does this sound like a collective failure? I initially thought it was an engine failure where it stuttered long enough to let the head speed drop. But this didn't explain the vibrations I was getting, nor did it make much sense as the engine had been running reliably all morning. As a matter of fact, it was still idling when I reached it afterwards. This is an OS-F 32 btw.

It's possible the link was thrown during impact, and I can't really rule that out. But something happened up there today -- something mechanical. It wasn't radio interference, and I can honestly say it wasn't dumb-thumbs (at least not today, anway).

Hopefully someone can tell me what it may have been based on my description.
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Old 08-19-2002, 04:24 PM
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Default Concept 30 did the chicken dance!

what do you use for training gear, if you use dowel rods, do not attempt FFF, if you get a burst of wind or quick cyclic movements they will shake and I have seen many heli's go down cause of them. the rods will make any vibration worse and if the rods can move in anydirection ( not tight enough) they will bring your heli down. just 2 weeks ago I was teaching my buddy to fly his concept and against my recomendation he tried FFF with his gear on. he was just doing circles around the field so when it happened we could see it. and acctually i think it started because of a burp inthe engine, it dropped about 2 or so feet and when he goosed the throttle it just started shaking and down she came. one of hise rods moved and we could see it the more it shook the more the one rod slid till one wiffle ball was against the landing gear. anyway I doubt the link came off in flight unslee it came off after the vibrations. i have lost a few during a crash. but also check all bearings for sign of vibration and if youare ready for fff loose the training gear

good luck
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Old 08-19-2002, 07:57 PM
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Default Concept 30 did the chicken dance!

Concept1, you may have hit the nail on the head. After discussing your theory with some other folks at the field, it seems like this may have been what happened.

Would that have caused me to "hear" the engine sag?
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Old 08-19-2002, 08:03 PM
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Default Concept 30 did the chicken dance!

Do you run a header tank? If not you might have turned your Nitro into a milk shake.

Just a guess though.
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Old 08-19-2002, 09:03 PM
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Default Concept 30 did the chicken dance!

No header tank. It sounds like this all could be a plausible explanation for the crash.

I just want to make sure it dones't happen again. Don't get me wrong -- I was really stoked to be doing FFF. I just hate to be grounded over something as silly as not taking off my training gear. Guess I should have asked on here before I tried it -- you guys could have saved me around $100.

The sad truth is that I've been flying my Corona for 2 or 3 weeks now without the training gear with no problem. Landing and hovering (nose-out) is no problem, and I probably didn't need them on the Concept yesterday, anyway. I was just thinking it would be safer to put them on -- sounds like they may have been the cause of the problem all along.

Thanks for all the input. I'll have her back in the air next weekend...
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Old 08-19-2002, 10:29 PM
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Default bsumpter

Sorry about your crash *sigh* HEY DO NOT
FORGET a NEW MAIN SHAFT while your at the re-build bud
10 TO ONE its bent. Take it off and roll it on a peace of glass
(for straightness)
Good luck KEEP FLYING!
Jeff
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Old 08-20-2002, 12:31 PM
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Default Concept 30 did the chicken dance!

How do you like the Corona? That was on my list to look into as a winter flyer.

THX-
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Old 08-20-2002, 09:29 PM
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Default Concept 30 did the chicken dance!

Cougar: Thanks for the tip. I went ahead and picked up a main shaft from the LHS today. Not too bad -- around $9.00.

pave-low: The Corona is a great little heli. It is harder to fly than the Concept because of it's smaller size, but it does make a great trainer for that very reason. After hovering the Corona, a 30 sized heli seems like a piece of cake.

It is also very, very TOUGH. I've crashed this thing numerous times with little to no damage. If there is a "dura-plane" in the heli world, this is definately it.

It is fixed pitch, so flying in the wind can be interesting. You just need to stay one step ahead of the collective in order to lock it on a solid altitude.

I've done quite a few modifications to mine to make it a little better. Go to: http://www.rcgroups.com/forums/showt...threadid=57046 to see some pictures.
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Old 08-20-2002, 09:42 PM
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Default Trainer gear-induced crash?

Glad to hear of this, then...
I haven't thought twice about doing a lap or two with them on.

Guess I'll stick closer to me (And the ground) until I'm ready to take the "gear off" plunge.
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Old 08-21-2002, 02:00 AM
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Default Concept 30 did the chicken dance!

Great face-lift on the Corona! I think I am going to buy the electric conversion for my LMH 110.

THX-
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Old 08-22-2002, 01:01 AM
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Default Canopy

The EP Canopy has worked great on my LMH 110.
Dose not crack.
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Old 08-22-2002, 01:09 AM
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bsumpter
Great pictures.
Were did you get the fan?
I wonder if that would help cool the V-max 6 in my 110?
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Old 08-22-2002, 01:34 AM
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Default Concept 30 did the chicken dance!

Joe K: The fan is a standard 486 computer fan. You should be able to pick one up for free or really cheap at any computer store. If you don't have a computer store local, you can get one at Radio Shack, but they are a bit pricier.

I'd say it would work great on your 110. You would probably have to rig a small battery pack to power it. It needs 12 volts, but of course mine is running on a standard 7 cell Nicd, so you can be under that cap quite a bit. A small lithium 123 or 234 pack should work great and add very little weight.
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