KC-Lovespeed

My Feedback: (26)

Today I saw something I'v never seen in six years of flying, unfortunately it was to my plane. Midwest Extra 300, moki 180, JR 4721 coreless on wings, digitals on elevator, rudder, weight 14 3/4 pounds. This was the planes second flight, had been up five minutes or less on this flight. Had just completed a knife edge pass and was setting up for another when the planes right wing Exploded completly ! (I was flat and level at this time) No warning of problems , no flutter sounds, just a huge bang and she rolled over several times before going in. Plane is a total loss from canopy forward. The right wing was never located. Yep nothing was found, no balsa, no servo, no covering. The pieces were so small they drifted away. After the plane went in you could still see tiny pieces of the wing still in the air ( was breezy). My self and the others at the field could not believe the wing disintegrated the way it did. While rolling over you could see a 1/4 of the right wing still attached.

Ok what happened here ? Could it had been flutter, and just so fast it wasn't heard. Poor building of the wing or poor wood in wing its self ? I am at a loss. Plane was very sweet, it needed no trim at all. Also plane had not been even pushed hard, loops and knife edge was only manuvers completed at time of crash.

branded

My Feedback: (9)

Probably flown full throttle in many manuevers that it cannot do at full throttle.

See this all the time...Guys flying beyond their skill level prompting a structural failure of an otherwise very sturdy, and fliightworthy airframe....

Else, a wing that wasn't built correctly.
Got epoxy?

You asked.....

KC-Lovespeed

My Feedback: (26)

Gah read my post friend. Only maneuvers done were a couple loops and one knife edge pass. Moki was only turning 8200 on ground so its not up to full speed yet either. And plane was level at 3/4 throttle. No diven no negative g maneuvers, no snaps............... was just maken laps, was only its second flight. Oh yeah, while some maneuvers I still havn't mastered, level flight, knife edge, take off and landing I can do quite well thank you !

DGrant

My Feedback: (4)

Ah man KC.....sorry to here about things like this. I've recently built that same plane, and do know how well they fly.
No warning of flutter, no strange happenings before the incident either??......wow.
I do have to say, like others might, with semi-level flight, the only thing that would tear a wing off like you describe is flutter. Unless the wing was structurally comprimised in the building process. From what your saying, it was definately handled gently in the air.
Did you build this plane?? If not, I'd be wondering and looking at all linkage, control horns, and anything that's left to inspect for failure. I've heard of the ailerons fluttering due to "less then adequate" hardware. I'm definately not saying that's the case, but only somewhere to look. The manual(actually the supplement to the manual) in the one I built called for 6-32 aileron horns(straight bolts through hard-points mounted in aileron). I questioned that one myself, and went with RocketCity all the way. That's 8-32. I have heard of the 6-32 letting loose before too. Just about a year ago, I ran across someone that lost one due to flutter, and he traced it to the control horn(6-32 bolt through aileron). When the kits first came out in early 90's they only told you to use 4-40 for those horns, then upgraded to 6-32 for newer kits.
Man...don't know what to say...that's got to hurt. Rebuild, replace...quick. Just learn as much as you can before you build again.

What I did with a smaller EXTRA(pictured in my avatar, it was totalled too), is I did what I call a post-mortom. I took it ALL home(I was able to find it all), and cleared out the shop. I spread that plane out in that shop as much as I could, and if something looked like it belonged, that's where it went. The NTSB, FAA, and all the rest had nothin on what I had going. Guess what? I found exactly what happened, after studying it. It took me a few days though, but it came together that it was rear-stab flutter that caused my catastrophe. Had I not done the post mortom, I might not have known, as mine happened very fast as well, and I didn't know what hit it. CHECK THAT REAR STAB TOO!!! Was it the newer version with the foiled stab, or older version with flat-stab? The flat-stabs MUST have flying wires..must must must. Point though is I built the next one(identical) and upgraded the weak points that failed in the first one. Still flying #2(identical to my avatar) with no problem.

Again, ,hang in there...these are tough planes to loose, real tough. They do fly incredibly well.
What kind of torque did you run on the ailerons? I'm not to familiar with JR specs.

Sorry,,,the more I think...I'm really thinking flutter for some reason. Do look into it in detail though, and let us know if you find something. I'm really curious. Again..sorry for the loss, but thank you for sharing.

Lee Belew

My Feedback: (2)

A couple of years back a good flyer and builder was flying a Pirate Models extra 300 100"wing. He does not punish his airplanes. He was flying near level when the right wing just past center toward the tip just exploded. I did not see the incident but the pilot said that there was no warning no flutter sound before the explosing. However he said flutter definately caused the problem. When the wing exploded the airplane was flying toward the pilot about 40 yrds away. He said that it looked as though the leading edge exploded but he knew what the real culprit was.

I also have a Hanger 9 Cap 232 1/3 scale in my shop that was torqued rolled on landing. I was examined the wing and the hinges. The builder put 13 large Robart hinges in each wing half.
the hinges are spaced at 4". The ailerons operate really smooth. I the the builder really understands flutter and is trying to avoid a disaster. The torque roll on landing had nothing to do with flutter.

Lee

Racapullco

KC....I have had that happen also, while not to the same plane as yours but I have had it happen to me 1 time. It was a Laser kit from MK so you can see this was a long time ago but even then I had 20+ yrs. of builing and flying so don't let the other guy ger your goat. We pays our $$$$ and we takes our chances.

Vince

My Feedback: (1)

Have to agree with the flutter theory. Did you seal your control surface gaps, and use heavy duty hardware? I almost lost my Sig SU31 on it's very first flight due to aileron flutter.

Sorry for your loss
Vince

branded

My Feedback: (9)

Sorry, GUILTY...I didn't read your entire post, you're right. DOH... Just when I think nobody's paying attention.

I can only say this.....

I've seen a few, one of which is owned by a friend of mine, and he really wrings it out in the air...Nary a problem. His has a Brison 3.2 gasser.

Who built it? Only the builder would know what the integrity of the wing is.... Did the builder install all the webbing?

Flutter can only be caused by a flexible structure that resonates at a particular frequency. The oscillations continue at higher and higher amplitude until the structure appears to explode, and fragment.

It's certainly not prevalent in the design of this model as it's been around for at least 4~5 years, possibly longer and we would have heard something about it by now.

This airplane (the kit) did have a problem with the stab snapping off in flight in early years but that was resolved by adding tail bracing.

My remarks about the possibilty of over stressing the airframe is prevalent these days with the advent of ARF's... Just ask the guys at SIG. They've had some problems losing wings on their Sukoi in midflight, only to find that the flyers complaining about the wing failures fly the model as they would their .40 sized trainers....

That's the downside of the Giant ARF's...They're "too" available to anyone that's got the money to spend, regardless of their skill level.

JMO......

KC-Lovespeed

My Feedback: (26)

Unfortunately the destroyed wing was never found at all . I could not believe the aileron or servo was not located. Does sound like flutter though. Plane had JR 4721 coreless, think rated at 90 oz. I used carbon fiber pushrods with Sullivan clevis. Hinge gap was not sealed, nor were flying wires used in tail. (Instructions did not state to use, nor was there an addendum). While hinges were not sealed , they were very tight, with no gaps. Builder of plane is a friend of mine and is top notch, he has built many planes over the years. Next Extra along with my just completed Midwest Cap will have sealed hinges. Thanks for all the imput, we can only try again !

radfly

Any birds in the vicinity? Or, was there any prior to your explosion?

DGrant

My Feedback: (4)

Ya know....it does happen to the best. Not to often, but yes...things happen. Good attitude my fellow flyer, might we all take that example. Let us know about the new one for sure.

branded

My Feedback: (9)

Well, no tail bracing? Just for my own edification (is that a real word?), what's the stab look like these days? Is it airfoil shape, or slab?

I know that at one time they did require bracing since the hardware to install it was included in the kit. In fact, we had a helluva time with it since the plastic jacketed tailwires supplied were looped thru metal brackets and caused one really bad "glitch" problem.

The plastic jacket (the type of wire used for Pull/Pull wire) over the wire was abrading in the hole of the metal bracket and causing metal/metal problems........

Smokin Cap

My Feedback: (49)

Do you fly near a gun range?....I have heard of a Gun club where "some" local gun club members take pock shots from their range which borders the R/C clubs field.

DGrant

My Feedback: (4)

FYI..on the flying wires/bracing...my EXTRA is of the older style kit(one of those oldies that I recently built) with the flat/slab stabs. The manual I have didn't originally have anything printed inside about the flying wires, but it came with a supplement and one of the additions was the flying wires, with that steel stranded cable.

Well...looking at the pull-pull system I bought from Don's hobby, and knowing the cabling is coated Kevlar, I couldn't go wrong with the stuff, I used the Kevlar for the flying wires. So, the pull-pull cabling, and the rigging for the flying wires is totally non-conductive, same stuff. I just measured and ordered the Kevlar in bulk, ordered the hardware...done. No prob. No soldering whatsoever, and simple crimps keep it together.

It seems to work well.

KC-Lovespeed

My Feedback: (26)

Nah wasn't "shot down" nor was a bird strike. I was only one up with five other fliers watching. In regards to the tail wire question, stab was old slab style. But there was no damage at all from canopy to tail. Fact looks so good I'm going to mount it. Looks like lose is going to be the plane, one JR 4721 coreless Trueturn spinner and pitts muffler. Not to bad considering. I chopped throttle and was pullen up so didnt go straight in, just luck there I'm sure as plane was rolling all the way down. The Moki 180 looks ok. Going to put it in my WM GS Mustang.

trailingedge

My Feedback: (1)

I can't deny it any longer. I was out dove hunting and saw a really colorful bird. I shot and it went down.... I only recovered a wing. I guess I didn't want the rest anyway cause that wing was really chewy.



I'm sorry for you loss man... hope I at least got a giggle though. Better to fly and crash than to sit at home and listen to the wife (laughs).

Tapio

I'm no expert on the subject but I'm wondering about aileron flutter versus total wing flutter. When I've seen ailerons flutter the wing remains intact, thus leading me to believe that servos or linkages weren't to blame. I would however suspect wing flutter. Maybe a bad batch of glue? I tested a sample spar on my 300, I wonder if a 5-10 G simulated sandbag would of detected anything before the incident?

Flypaper 2

I would suspect wing flutter also. Saw a model Reno racer wing explode in about 2 frames of a video clip. I'm sure some of you have seen the clip of the full size stealth fighter wing disintigrate.It flapped about 3 times before it blew apart.

rcpilotjae-RCU

My Feedback: (21)

Woudn't it be nice if the machine guns really worked on our war-birds and we could take "pock" shots back at the fellow who think it's fun to shoot at our planes?

Just a pipe dream.....Sorry.....


I would suspect flutter also.

tailspnr

My Feedback: (1)

Just a word of warning. My absolutely beautiful, static display winning, prestinely built, Midwest Cap 232 suffered a fatal blow because of wing flutter. It was it's second flight, NO fast or harsh maneuvers, I was babying my new Moki 2.10, and in a power off descent...not dive....descent, I heard and saw the flutter on the right wing. I immediately attempted to slow the plane and bring her in but before the flutter would stop the right wing stalled...naturally. And the Cap rolled over from bout 30' in the air and took out the right wing and broke the fuse. I have all of my components and upon inspection I noticed the small piece of hardwood thats glued to the leading edge of the aileron and between the aileron sheeting simply pulled out. This is the block that the aileron control horn is screwed through. Now maybe I didnt have adequate glue to the hardwood block to the leading edge of the aileron and sheeting, but after inspection I just had my doubts as to whether or not this was a good design. The plane did have all of the control surface gaps sealed too.

If I had it to do all over again I would certainly reinforce the inside of the aileron and the increase the size of the hardwood block. I know these planes have been out for a while and certainly we would have heard of this had it been a known problem, but I built mine, and built it right, and I hurts like you know what when you see that baby on it's second flight bite the dust. I hope this atleast give you something to look at.

I can maybe get some pics of it if anybody is interested. If so let me know and I can post 'em here. I currently dont have a battery in my old digital camera but you'd like to see pics I'll get one.

Scott

DGrant

My Feedback: (4)

Tailspnr....I know just the ones your talking about. They tell you to add the hardwood in between the ribs, epoxying to the bottom sheeting. I saw this as a prob from the start. What I did, was fashion a piece that spanned the distance in there(rib to rib), and built it up so there is contact all around it(top and bottom). Then I used RocketCity 8/32 hardware. I'm hoping this is safe enough. BUT...I totally agree, the wood that bears that block will just break, because unless it's beefed up slightly(It doesn't take much at all either), it will literally be ONLY as strong as the sheeting. Watch out for this one.......good point Tailspnr.

smartman300

My Feedback: (4)

I think I know what happened. I know a guy that flew his plane straight and level, and the whole covering came undone on the leading edge, and one side of the wing just exploded like a balloon.

needless to say, he seals all his leading edges now.

rfw1953

My Feedback: (2)

Not the same airplane, but same end results. Last year at our annual Big Bird event I had a wing shear off after doing a hammerhead stall with multiple spins with no power. As I pulled out of the dive and began to add power the right wing sheared off at the wing joiner. This was on a G.P. Giles 1/4 ARF with an OS 160 FX. Not over powered and no detection of flutter. Post crash analysis was that it must have been a bad piece of balsa. I guess it happens. I have seen guys fly the same airplane much more aggressively than I do, so it's hard to think it was something about my flying habits. Sorry to hear about your loss. I guess it comes with the hobby. My wife wonders how this can be any fun after putting so much time and money into even an ARF. I understand her point. It is very frustrating, but it sure is fun when it goes right. Good luck on the next project.

daveopam

My Feedback: (9)

My story is going to sound a lot like yours.Second flight Midwest Extra (the old one with flat stabs) ST 3250. 3rd pass straight and level at 2/3 throttle. Right aile fluttered twice and started flapping in the air. Wing stayed together but plane was barley controllable. Made a turn at the south end of the field to try and land. After trying to line up with the runway the bird was 40ft up and heading straight toward a bunch of guys standing behind me. With little control I decided to push it in. I gave full down elevator. To my surprise it came out the other side inverted. I tried to roll it and set it down going away from me. By the time it rolled to gear down it was to late. All the airspeed was gone and it pancaked hard. Totaled the airframe, spinner, muffler. cowl, ect........ This all happened two years ago. I've learned since the original design had a lot of AILE problems. The linkage and bolts given were to small. Plus the tray were the servo mounted was only attached on two sides. The 300XS is attached on all four and has larger push rods. The strongest servo in the world won't help if the tray it's mounted on flexes.
If you decide to build another one the new XS version is twice the airplane. After looking at the building time on a new one I bought a ARF. The SIG 1/4 scale Suhkio. It's about the same size and cost the same as the kit plus covering,fiberglass, paint, ect..
Good luck and keep your chin up, David

Patriot

I was digging through old threads looking for some info and couldn't help but run across this unfortunate incident which I can't help but comment on.
I have learned a little about the physics of aeronautics since I was a kid, and building models for years. I actually got on the phone with my brother who has a masters in aeronautical engineering and is a Captain for TWA. I talked with him extensively about why wings have a tendency to explode when manufacturers are in the process of testing new wing designs. What we both came up with seems to make the most sense when we use some referances to Lockheed experiments that he studied.
It all comes down to the basic understanding of "Why a wing works." As experienced modelers, we all know why a wing works, so explaining it here is preaching to the choir.
But, why a wing explodes for no apparant reason is another matter all together, yet none-the-less tied to the original physics of "Why a wing works".

Essentially what we need to remember as modelers is that our airplanes are made of very light materials. Specifically, balsa wood. Remember, balsa wood wing ribs have their grain running horizontally, not vertically. They need to handle some compression and some radial forces placed on the wing when perfoming aero-batics. But, what alot of guys forget is that, the wing also needs to be able to handle expansion. Sounds crazy doesn't it? But, none-the-less true.
As the wing travels through the air, a pressure differential is created across the wing, specifically from bottom to top. The bottom of the wing has a higher pressure than the top due to the the air travelling faster over the top of the wing. Thus, lift is created, and the wing functions as desired.
However, what we forget is that there is air "INSIDE" the wing as well. This air is generally non-turbulent due to it being fully covered and basically sealed off from the outer world. Sometimes, their are holes in the ribs to allow for servo wires, thus allowing air pressure inside to equalize with the outside. But, even when pressure equalizes to the center of the fuse, the fuse is sometimes sealed from outside as well.
If there are small holes in the ribs and very small air passage from the fuse to outside, then the wing inner pressure may not be able to compensate fast enough with rapid changes in pressure outside the wing to prevent excessive expansion.
So, what may have very well happened here is, even though the wing was flying along straight and level, the differential in pressure inside the wing to the low pressure system on top of the wing became so great, that over time, the soft balsa ribs simply began to split down their length as the wing basically began to pull itself apart.
As more and more of the ribs began to slowly split over time, the problem propagated into something that resulted in complete catastrophic failure of the overall structure. Thus, the wing basically EXPLODED!!!
The plane now is long gone, but my guess is that if some of the other wing was still intact after the crash, uncovering it and inspecting the ribs for longitudinal splitting would have most liekly been evident on that side as well. It just didn't fail first.
I hope this gives some thought to why these things happen, even when we don't do anything wrong.

Patriot