Well, its been 3 years since I started flying, and this is the first crash that I won't be able to repair.
I will have to say pilot error, because I guess I shouldn't have a .75 in .46 U-Can-Do.
When I was a little boy I used to spend my summers (in the 70's)in Oakdale Long Islnad, and there was a guy who I was related to by marraige (very distant cousin) who used to fly planes. Everytime I heard the plane, I would get on my bike, and ride to the beach where he was flying. Usually by the time I got there the plane was crashed already. I think once I saw one fly from a distance for about 5 seconds.
Anway, I used to go to his house to look at the planes, and he opened up his shed, and it was piled 2/3 the way to the top with crashed planes. I still remember that B-17 in 3 pieces.

That is where my first inspiration to fly was. Its been all these years, and I went back to that spot to spend the weekend, I haven't been there in 12 years. So I took my plane. First flight, it was a bit turbulent, and the field was a bit small. I had to fly out over the water at times. So I'm doing this knife edge, and I guess I was going to fast when the elevator started fluttering bad. I cut the throttle so quick that I don't think it fluttered more than 10 times. But right after that, I had no elevator and into the Great South Bay it went head first full speed.
The wind was blowing away from shore, so I quickly ran to the water, and took off most of my clothes and started in after it.
It was pretty smashed. I think it hit the water in a shallow spot and actually hit the rocks as well. To add insult to injury I cut my foot open on something in the water, now I'm limping lol. The plane is pretty well trached, but I think the engine is ok, and maybe the reciever and aileron servos. The rest is going to the garbage.
The funny thing is the elvators and servos all appear to be intact. There was a servo matcher in the plane to match the 2 elevator servos, I wonder if that blew out when it fluttered. Any suggestions to what happened? I haven't had a chnance to test everything yet. There will be an accident investegation. I will let you know what I find. I was using futaba 3004 servos.

I guess you're right.

Those servos are a little weak for that aircraft. I've seen casual flying with a .40 Stick strip the gears of a 3004. I would start my investigation there.

I use 3004's and I think they are great servos. I have used them in everything from my J-3 cub to a Sukhoi SU-26 powered by a SuperTigre .75. I cannot agree with the last post about them stripping that easy. Maybe that guy just had bad servos to begin with. Mine have lasted forever and still perfrom like new. I would look more at what you mentioned first as the cause of the failure more that I would the actual servo failing.

I agree. They are great servos. I had them in my SIG Somethin' Extra until the wings flew away but that's another story and not the servo's fault.

Antslake and I belong to the same club so I know the plane in question and I know how he flies (flew) it. A 3004* will not survive on that plane** when flown at high speed with a .75 size engine.


* rated 44 oz.-in. at 4.8V
** GP requires 50 oz.-in. *minimum* with a .40 size engine at slow speed

Ok, I was using 6.0 volts.

Also I realized something. My second flaight with that engine, the throttle barrel retaining screw started backing out, and my plane got locked at full throttle for 10 minutes. The 14x4W prop tips were starting to go supersonic, it was flying so fast. I didn't have a problem with control flutter then, so I thoght the plane was ok.

But that was at about 700ft alttitude. When I brought the plane down to sea level, I was noticing a lot more power. Also being in a knife edge, probably helped the elevator experience more turbulence.

Do you think there is a way to set this plane up so that doesn't happen again? I really like having all that power in a small plane. But if there isn't a way I guess I will just get a ucando 60.

I still haven't done my investegation, been too busy working.

My Fluttered on its maiden. Not because I was overpowering it (Witch of course I was) but because the horizontal stab was too weak. I had to reinforce it with plywood. The 3004 should work fine, especialy on 6.0 volts. Im using 3001 on elevator and aileron, HS 545BB on the rudder. The only difference between the 3001 and 3004 is the 3001 has one BB and one Brass Bushing. The 3004 Has one BB and one Nylon bushing. I would check the slop in your servos on a regular basis as they tend to wear out quite a bit faster. Make sure all your pushrods and likages are nice and tight. Im using carbon fiber rods on mine. The stock pushrods were just to flimsy. This may have been part of the cause of your flutter...

Is says U-CAN-DO-3D right on the wing!!!
Not U-CAN-DO-PATTERN!!!!!
servos & big motor are not to blame hear.
This plane is built to fly low and SLOW.

You said yourself you got going fairly fast, speaking from experience, I'd have to say thats it. I have the same .46 plane with a TT .91 4 stroke + digital servos on the tail +4-40 linkages. If I fly at 25-30 mph. the counterbalances on the elevator start to catch the wind and flutter.

Plus, to make matters worse, it sounds like you were destined to crash since you were a lad!

Geeze, Joe... Don't hold anything back.

It really wasn't going that fast, but since it was in a knife edge, and I had to apply a little down elevator, the moment I added the elevator, it fluttered. So a combination of prop wash and turbulence from being in a knife edge, plus the speed required to do a knife edge, it made the surface flutter.

I have flown the plane faster without having flutter.
I also have flown it knife edge with the last motor it had, a magnum 4 stroke .80 at full speed up and down the field without flutter.

Ive been flying for quite a while, and I have to give my two cents worth.

A lot of people automatically blame servos, radio, hinges, control surfaces etc.

I got a little tip for you. Check your pushrods.

At high speeds the pressures generated on the surfaces can be sufficient enough to flex or bend the pushrods. When you crank in more (aileron,elevator,etc) into servo, instead of it moving the control surface it just bows the pushrod more. You may want to try stiffer pushrods, or reinforce them by putting guides along the length to keep them from flexing.
Anytime a plane goes in due to high speed, and there is no apparent damage to the servos, and all the linkages are still in place and fixed tight, its a pretty good bet that the pushrods were flexing. If the pushrods didnt flex, you would probably have a stripped servo.

This would explain your flutter problem. When you applied down elevator, instead of it moving the (difficult to move, due to high speed) elevator, it flexed the pushrod, and the springyness of that bent rod, will make the surface flutter like a butterfly as it flexes and straightens.

Just my two cents worth.

I dont know if this will help. but a friend of mine had his Magic 3D down at the field, we started the engine and taxied to the runway. As he throttled up, the ailerons fluttered and were completely uncontrollable. good thing was that the airplane was on the ground and it just started to gain speed, we had enough runway to slow down to a stop. We at first thought it was interference (did you experience that? it looked just like the movement that happens during interference) and so we checked the channels. they were all fine. Because of this incident, we only flew EP's on that day. He came back the next week telling us it was metal fatigue, the stab that holds the control surfaces was too old and they started to cause the ailerons to be uncontrollable.

I dont know if my post will help you at all since your plane is probably in the dump now, but for the future, remember to check for metal/rubber fatigue and check that all the bolts and screws are well secured. Even though it might take a little more time, it would make you do the 3-D's you want for as long as you like!

I think it could be the pushrods like bdavidson said.
I still have the plane, and the back half is intact, I just haven't had the time to test the servos. I doubt they work, since they landed in salt water. They appear to be fine, and in the correct position, without stripped gears. So something else made them stop working.

The flutter was extremely violent, and I guess anything could have happened, I was so disgusted when the elevator didn't respond, I really didn't touch any other control, I think I had already cut the throttle to slow her down, and the ailerons respond by turning the plane 180 degrees the other way. Had I been smart enough, and the rx still working(don't know if it was) I could have put spoilerons on, and maybe had enough lift to fly the plane back in. But I was only about 100 feet up, and was so shocked that the plane stopped responding.

Well, I completed my post crash investegation. I didn't even open up the rear servos, because I intend to chuck them, after they were in the salt water and all, but the complete rear of the plane works fine. All servos in right position and no bent push rods.
I will have to say due to the weak linkages and low output of 3004's that it just fluttered, just like the instructions said it would, lol. The resulting flutter was so violent, that something else must have came loose. It sounded like a jack hammer hitting the plane, I will never forget it.

There's a guy at our field who flies a UCD 46 with a Saito .82 in it. He gets elevator flutter every time he dives the damn thing at more than 1/2 throttle, and has been very very lucky so far that nothing has come off. He uprated his pushrods, and has cured the problem, but it was very unsettling to hear that "brrrrppp" every time he forgot to dump the throttle when he put the nose down....

I also use 3004's on everything, with a few 3001's mixed in on alierons, etc. A couple months ago I was preflighting my .40 sized FW 190, and noticed one of the alierons was acting strange. Sure enough, stripped gear in the servo, but I'm betting it was hangar rash, the wing got knocked over by the helpful cat, and probablly landed right on the alieron. Shock loads wil do it every time.

Andy

I have a modeltech me-109 25size with a mag52xls 2 stroke ,futaba 3003 servos....with a 4.8v battery and it doesnt seem to flutter and the servos aren't stripped. Only servos that I had problem stripping were hitec servos...forgot which ones I had tho...I just gave them away.