Hi everyone. I have been in the hobby now for about a year and yesterday I had bad experience that I’d like to get your reaction to:

I was flying my BTE Venture 60 (first kit), pulling out of a large loop I heard a loud buzz that lasted lasted for a second or two. I then lost elevator control and crashed, destroying the plane and damaging the engine.

After inspecting the wreckage I found that the elevator servo’s gears were completely stripped which was why I had lost elevator control.

My guesss is that the elevator developed ‘flutter’ which stripped the servo’s gears which, in turn, left me with no control over the elevator.

When I built the plane I was aware of the possibility of flutter problems as I had read one or two internet postings from people who lost their Venture 60s to this. To minimize slop I located the elevator servo on the aft of the fuselage and connected it to the control horn with a heavier gauge control rod than was included with the kit.

I called Bruce Tharpe who designed and kits the aiplane. Bruce told me he had heard of only two or three instances of this happening with the Venture 60 kit. He suggested that adding a second control horn to the other side of the elevator might reduce the possibility of flutter, He also graciously offered to sell me another kit at half price if I was interested in building another one.

So here’s my question: Should I build another? One the one hand I loved the way it built and flew (all 4 flights) right up to the moment of impact (actually about 10 seconds before impact is when I stopped enjoying things…).

On the other hand it makes me nervous to think of investing all that money, time and effort again not knowing that the flaw that caused the flutter (whatever it is) has been fixed. Right now I have no idea of what to do differently next time around.

What would you do if you were me?

Second, can you give me any idea of what might have cause the elevator flutter?

Did you seal the hinge gaps?

Was there any slop in your elevator linkage?

What type of hinges did you use?

I would probably take him up on it. Sounds like a good deal. You can stop flutter problems on anything. Have an instructor help you set it up if you have questions.

One other piece of advice, when you are going down, and there is nothing you can do, chop the throttle, but don't stop flying the plane till after it hits the ground. With no power and other control inputs, you may slow it down some and save the engine. Doesn't always work, but it is worth a try.

Don't give up.

toucano-

I used the included easy hinges, I did seal the stab/elevator gap and checked for play in the elevator linkage- it was tight.

The elevator is a split design with the left and right halves connected with a piece of (heavy) wire. Could the flutter have developed in the half of the elevator without the control horn?

George

FLYBOY-

How can setup be adjusted to eliminate flutter? (assuming no control slop, sealed hinge gaps etc). All the flutter problems I have heard of usually result in catastrophe so trial and error won't work...

George

George,

SLOW DOWN!!

Cdallas2 George,

SLOW DOWN!!

What? Airspeed? Throttle was at idle.

Maybe it was just a bad servo???

Maybe it was just a bad servo???



Maybe. I suppose it's possible that the servo started failing which allowed the flutter to develop which then quickly killed the servo. I don't know enough about servos to say how likely this is...

Have you thought about using metal gear servos?
It would be worth it to build another one. The second one will build faster because of the experience factor.
I would use Hi-Tech metal gear servos for the elevator. You could use two servos, one for each elevator half.

tony

handsfam,
sorry about your loss, very possible that all of the above suggestions are true. you did the right thing upon examining the wreckage. i would buy the second kit anytime you can get something 1/2 price i would call that a good deal. also see if engine can be repaired. lol

john

the venture is a wonderfull bird, be sure that your loss (sorry for it) is not due to a design problem.
jump on bruce's offer and enjoy that wonderfull plane.

I just thought of something:

The building plans call for a .65 - .80 4stroke. I put in a Saito 91FS. Could that have caused a problem?

Handsfarm: not familiar with that plane but there are ways to stop the flutter. Instead of using wire across the elevator halfs, I use aluminum tubing grooved into the front of the halfs till they are flush with the LE. Wrap 6oz glass cloth around the front and onto the elevator about 1/2 in. Build the elevators as light as you can. What are they made of, Like how thick?

A .91 four stroke in the nose of a venture 60 is just fine.

Forgot something. Use thick CA on the glass and roughen the alumunum tube with sandpaper ,never had one come loose.

Flypaper-

What is it about aluminum tubing that is better than a wire?

The flutter was either a building error or pilot error. Not bashing you because it's a common problem among new builders. I've lost two planes to flutter - both were my fault.

You have to keep that hinge line tight and preferably sealed. Use at least 3 hinges on any control surface. For example, if there are two elevator halves connected by wood or wire, then three hinges on each half minimum.

No slop in the pushrod. If the servo has a lot of slop in it then don't use it. Get a new servo, new gears or whatever.

Keep the control surface as light as possible. Square off the trailing edge of the control surface so air breaks cleanly from it. A rounded trailing edge will contribute to the potential for flutter.

Lastly, learn to use the throttle. The new 3D models are designed to be very light and over powered. That power is there to pull vertical - not to be used for speed. If you were to hit the throttle on some of those planes in level flight or a shallow dive you could probably kiss the plane goodbye.

Handsfam:
The wire is like a torsion bar suspension on a car acting like a spring. The tubing acts like a drive shaft on a car. Won't twist. How thick is the front of the elevator?

Eyeballing it, it looks like 1/4 inch

I'd say about 1/4" -Why?

I was concerned because the larger the diameter the stronger it is. 1/4 in is fine. I have used 1/4 in carbon fibre too, which is much stiffer yet but is harder to come by. Better to use two layers of glass on one that size. Went to the BTE website to check it out. Nice. A lot of elevator area. Needs to be built as light as possible even if you have to replace heavy kit balsa for lighter wood. Built up structure would be even better but more work for lighter weight.

Seal the hinges lines, use quality servos, make sure there's minimal play. All good ways to minimize the chance of a flutter failure. Get the half price plane and jump back in the saddle.

Not to toot the BTE horn, but those kits probably have the best wood in the universe. You'd be hard-pressed to improve the wood selection.

I'd also look at other causes for the flutter besides design: Bruce Tharpe designed the 4*40 and other kits for Sig and knows how to design.

Thanks for all the good observations and suggestions, everyone. Based on the input I plan to build another Venture 60. Like Lee Majors, "I can make it faster, stronger....better!" (Well, maybe not faster).

Below I have pasted an email exchange with Bruce Tharpe just for your interest. I couldn't have asked for better support and service.

I have also attached a photo of the decedent.

> Hi Bruce,
>
> I called you yesterday with my sad story of losing my Venture 60 to >elevator flutter.
>
> Although I'm still grieving the loss, I'm sure Venture 60 #1 would like me
> to go on with life, so please let me know when you have more kits available.
> I will take you up on you generous offer to sell me one half off.
>
> Ironically, the only surviving part of the airplane was the empanage. I
> still have it in my garage. I cannot bring myself to throw it away...
>
> George Hands
>
> PS My wife thinks I'm too emotionally involved with this thing. You don't
> think so. Do you?


Hi George,

I know you're half joking, but still, just ask your wife, "If there wasn't any emotional attachment, what would be the point?" I'm honestly flattered that you were so proud of your V60 and understand completely the grief that comes with losing it. We've all been there for one reason or another.

As I tried to explain on the phone, flutter can be a cruel and indiscriminate enemy. I've seen beautiful planes built by experts fall victim to it and pieces of junk that look like they're ready to flutter just sitting there do screaming passes all day without a hint of it. It doesn't seem fair. Flutter requires excess airspeed and/or sloppiness in the system. That can include the linkage, the servo, the hinges, and the structure. It's hard to gain excess speed with a V60, and over the phone your setup sounded okay, that's why it's so tough to determine the cause.

I'll sure let you know when kits are ready and we'll get you going again.

Regards,

Bruce Tharpe