A CAI Raptor ,on its first flight, fluttered and crashed this weekend. This plane was one of the best looking Raptors I
had ever seen. It was a single seat, painted like a Blue Angle.
NICE


Here is what happend. The whole wing fluttered, on both sides.
It happened at ~180, the plane slowed down
when the flutter started, nothing left the plane but
it was uncontrollable and nosed down and hit the
ground at about ~100. It did not roll much and the outer
wing sections, past the gear were making a very loud flutter sound and you could easily see the wings were a blur.

The first reaction was the aileron, linkage broke,
ect, but I saw the linkage, and I know the guy who built
it. All the equipment was top notch. Next to no slop ect..
This should not have happened. I am confident it was not the
builders fault.

This is not the first time this has happened to Raptors
and I want to know WHY. I design a lot of planes and
I would not want this to happened to me. Since CAI
is no longer selling planes, there should be no harm in
trying to figure out want went wrong.

The (rumor) is 3 of 4 CAI F-100 did the same thing. WHY ?

I have a theory.

Think about this. Your in a 747 sitting even with the wing.
You can see the wing moving up and down, and twisting.
If the 747 were to pull 2g's, the wing would bend up
and also twist some to give it washout.

What would happened if instead of washout as with wing
bent up, the wing would twist and produce wash in ?
I think the wing would start to flutter or just break off.

So... I clear you must build a wing where as you load it,
and it is bent it up, it twists in a manner to decrease
the AOA near the wing tip.

All CAI wings were molded top and bottom with glass and
balsa witch made a very nice, stiff, strong wing. This made
a hollow wing witch used a laminar flow airfoil where
the thickest point was farther back than most model planes.

All wings will twist, loaded with G forces they twist around
the axis of rotation for that wing. Its just a line that
the wing will twist or rotate around. Remember, at 200mph
it only takes ~0.2 deg AOA to fly.

I think the axis of rotation, was behind the center of lift....

Was this a problem in the past with full-size aircraft.. ?
Does anyone hear of this problem before.. ?

Eddie Weeks
http://www.corpcomp.com/weeks1/

Lack of torsional stiffness is the usual culprit when a wing flutters. I should know since I've lost 2 molded aircraft due to wing flutter. In the post crash invesigation I saw that there were no layups on a bias . I couldn't believe it !!! Check the Raptor remains and look at the layup. You might be surprised !

I believe that Eddie is correct about "I think the axis of rotation, was behind the center of lift", but I think there may be more to it. If it was only that, a divergent situation, the wing should just break off. There is a more complex dynamic element here, most likely that the aileron gets into a mode that causes the wing/aileron system to tune up at a certain speed and all hell breaks loose in the form of drastic, full side of a wing flutter. Very bad news. What does everyone think?

I think Mark is correct. What Eddie describes is similar to the X-29, forward swept wing. The wing would just rip off, not flutter.

I seemed to remember hearing that the thickness of the ailerons on CAI stuff did not match the TE of the wing. If the control surface is thinner then the wing, doesn't this excite flutter? Probably one side started to flutter first, and the vibrations kicked the other one into flutter.

Just a thought..

Tony hit another point there.. If the ailerons are thinner than the trailing edge of the wing.. it can increase the possibility of flutter a great deal..

I've had 2 wing flutter incidents, not on jets thank goodness, but on electric gliders. The flutter occurred in vertical dives at 154mph plus, Iam sure of the speeds because we were using a radar gun to measure the speed at which the flutter started.
The wings became a blur but did not depart from the aircraft.
This happened with a composite moulded wing and a veneer foam wing, both were supposed to be unlimited performance wings, I was carrying 24 cells in each glider.
My conclusion was that the flutter started at the wing tips due to lack of torsional strength at the wing tips in both cases.
It's a very frightening experience, I had no control whatsoever until the speed decreased and the flutter stopped.
I'm open to other interpretations of the cause, the ailerons were hinged continuously with the top surface of the wing.
Hope this experience helps

Mark Diggle

From what I remember (may be wrong) the plane was
perfect. The thickness of the wing match the aileron
and the builder molded his own pockets for the aileron.

Another note: The raptor wing is a very heavy wing
weighing in at around 10lbs...
Isobar wings are far lighter and not near as strong.

I agree with Rocketman about its likely for more complex
than what I discribed.

All other planes have ailerons with the same linkage
and there not fluttering. That is why I think its the wing.

Eddie Weeks

A very heavy wing probably means very heavy control surfaces. If the wing is low on torsional strength, that's a perfect set-up for flutter.

It amazes me that we get away with as much as we do considering we have unbalanced control surfaces and somewhat flexible actuators.

Eddie


I think these issues have been a factor since Orvile and Wilbur got out of the bicycle business. It takes alot of R&D and knowledge to overcome such obstacles but unfortunately there are some people who try to market their products before they have proven themselves and the product. I know of one man who has gone above and beyond the call, to insure his product is as safe as it can be right out of the box. You get what you pay for, and as we all know there are no short cuts to this sport... I do think that you are right on track with you thinking..but I do believe that the above mentioned individual has thought about this problem and made sure his kits are correct.

see you in waco.


Doug Arnold
Dan Massey

heavy control surfaces take on a life of their own, especially if they're not properly aligned with the mating surface or if the gap is too big. b.v. has it right ,keep it light, keep it tight

FUBAR...

I was there this weekend with Eddie and saw the plane before, during, and unfortunately after this incident. The plane was very well built. The owner is an excellent modeler and had gone to extra effort to make sure the linkages etc... were done correctly. The ailerons were hinged using scale hinging, similar to the way BVM does the Phantom, and F-100 hinging. I did not grab the control surface but it appeared to be built right. I can not speak for the torsional rigidity of this wing but I did have a Razor in my shop for a short period of time and I thought it had a very stiff, and heavy wing. It is a shame the airplane looked really nice.

DR

On my Raptor, the ailerons were the correct thickness - its the elevators that were a full 1/8" thinner than the stab. One day when I was on the phone with Scotty Bolduc, he was candid about that and admitted that it was wrong (he had different guys doing the moulds for each part of the aircraft, and the guy doing the stab was "less experienced"!?). Next time I spoke to him he denied the above, and said that there was nothing wrong with the elevators.

The first wing that CAI sent me got damaged during shipping, and that allowed me to see inside the wing. The spar was glued only to the top surface... not really a confidence builder.

Unless Chris Huhn's availability changes between now & Sunday, Sunday morning should finally see the first flight of my Raptor. After building the aircraft, I decided that Scotty's description of the Raptor as a perfect first turbine aircraft might be as inaccurate as his claims that the kit was high quality, so I hung it up while I played with the Bobcat. Now if Chris & I can just be available on the same day, we can get this puppy airborne.

If nothing else, the act of finally flying the Raptor may at least open up some space in my trailer for my new Super Bandit ;-) So - this might be the last photo ever taken of my raptor...

Later,
Gordon

Don't worry about the Raptor it will fly just fine. Been flying one for 2 years now and it flies great. Mike Haddox

First of all not all Raptors have this problem, this one Gorgeous Raptor was being flown for the first time with a wing that that was never sold to anyone, this was the first time it actually flew as some beefing was done to this one particular wing by the manufacturer.
I never had problems with my Raptor as many of you saw I had at Superman 2 yrs ago and she's still flying with its current owner.


Regards............Johnny Hernandez

What do you mean Beefing done by the manufacture, why was this wing not sold to any one? Was it a reject wing or damaged in shipping and repaired? What gives on this deal? DM

Not that it matters, but here is the plane.
Note how well the aileron fits the wing.

There is a big problem with my theory of the
crash.... There are quite a few Raptors flying
with no problems. If it was design problem,
all of them would flutter assuming all the wings
were built the same way.

Eddie Weeks
http://www.corpcomp.com/weeks1/


ps... the Rig is going to SWFF

one more

Damn, that thing was BEAUTIFUL!!!

A lot of Krylon cans, eh? (just kidding)

Eddie;

Your description is that of a wing that flexed under flight loads, and due to continuos oscillation and MAY BE lack of glue in the spar area, it prevented the wing from stopping to flutter. Since there is no damping at this point, the wing will continue to oscillate to failure. Aileron flutter seems not to be the cause from your observations. There was some talk ( as above ) of some wings that escaped proper gluing processes.
I have a Razor composite kit and one day I may finish it or sell it, but overall I am not happy with this product's quality and this does not make me feel any better

A few years ago, I was watching a Giant Scale Race Video. I saw Bill Cunningham's plane fold a wing. In slow-motion mode, you could see the tip flexing on one wing panel through about +/- 20 degrees AOA! Then the wing folded and the tips touched! A couple years later during my masochistic era when I flew pylon, I was test flying a Q-40 with a "new" composite wing and the wing folded DOWN and the wingtips touched during a straight and level pass! The kit mfg. told me that it was my fault! Later that year at the Nats, his wing folded as well. Too bad... The point is, looking good on the outside sometimes has nothing to do with what's gonna happen at "cruise" speed..the devil is in the details of the kit production and quality control.

So sorry to see such a beautiful model go down.

Regards,

cactusflyer

Ahh, sweet sweet irony. Please please tell us that you called the manufacturer and laughed into the phone, PLEASE!!!

I am still waiting of Jetflyer 24 to elaborate on his post. what does he mean by beefing done by the manufacture. and why was this wing a one of a kind.

Doug A

woketman wrote:
Ahh, sweet sweet irony. Please please tell us that you called the manufacturer and laughed into the phone, PLEASE!

Well, actually, since you ask, there's more to the story...The fuse actually survived the crash...as it was heading down range ballistically with no more wing, I gave it full ruder and elevator and it came down like a maple seed...helicopter style!..no damage except for a broken prop..Honest..I have witnesses! It was a week before the Nats and this WAS going to be my back-up plane. The mfg. said he would "help me out" and bring another wing to the Nats and we could screw it on since "they so accurately built". He said it would only cost me around $225.00 for the "new" wing. After I witnessed his "bad luck", I seemed to have misplaced the invoice....the mfg. didn't pursue it any further...now let's get back to JETS!

cactusflyer

Are those composite wing structures hollow with the spars internal?

It seems if this is the case the glue joint at the spar becomes so much more important! With a balsa or foam structure wing, there are many more areas loads can be dispersed.(entire surface area of the foam or across ribs/spars

Mike