220lb RC Jet Plane Disintegrates Midair

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If you think your Monday sucks, watch this video and you'll instantly feel better about how your day is going. If you are really pressed for time, fast forward to the 1:45 minute mark.
 
My Krauts love giant scale RC, but personally when you get to half scale aircraft, I don't understand the point when you basically have something big enough half the time that a person could just fly INSIDE the aircraft. BTW, I think what happened here is the guy didn't have servo saver type device installed, and so when there was too much force on the rudder, it ripped the whole thing off instead of just losing rudder control. :(
 
sad.

I experienced structural integrity failure yesterday during a maiden flight of a blu-baby 33 as well. AUW is 8 oz including lipo. Very nice light foamy model that just floats. The single sheet of foam that comprised the wing snapped when I was about 40 feet in the air doing a simple loop.

Thankfully, a 1 minute repair job fixed it and the motor was ok.

Lesson learned again though, even if you think you can do high-G maneuvers, doesn't mean you should. That's what 3D planes are for.

RCG thread

As post #6 clearly shows, the vertical stabilizer was surface mounted on the skin of the main fuselage or very close to it. That is poor construction technique on a model this size. As you get bigger, the structure must also borrow from the full size more and more or the airframe cannot stand the stress. The person who built it seemed to think what works on small models works on big ones. True for aerodynamics, not true for stress.

Tail disintegrates, then when the nose pitches up, the wings disintegrate. It was just a matter of time before this thing broke apart, given the combination of power, airspeed and weak construction.
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  • Vertical stabilizer separates.
  • Plane begins to yaw left = nose up.
  • At about 45° slip angle, it starts to roll left, continuing pitching nose up.
  • Next couple of pieces separate at about 60° AoA, wings almost level, pitch up continues.
  • The whole thing blows up at about 90° AoA.

Certified or not, that thing had some serious structural issues.
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J Macker said:
sad.

I experienced structural integrity failure yesterday during a maiden flight of a blu-baby 33 as well. AUW is 8 oz including lipo. Very nice light foamy model that just floats. The single sheet of foam that comprised the wing snapped when I was about 40 feet in the air doing a simple loop.

Thankfully, a 1 minute repair job fixed it and the motor was ok.

Lesson learned again though, even if you think you can do high-G maneuvers, doesn't mean you should. That's what 3D planes are for.

RCG thread
Click to expand...

I like watching those indoor foamies. Here's one, he doesn't get going good until 1:30



I like watching the guy

 
Dullard said:
I like watching those indoor foamies. Here's one, he doesn't get going good until 1:30
..
I like watching the guy
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Holy crap! how does he do the maneuver at 1:23-1:25 in the first video?! (hammer-like motion)

And how does he reverse (backup) the plane at 1:36-1:42?

I've never heard or seen of planes backing up like that. of all the ESC's I've used, there's never an option to make the motor spin in reverse. You'd have to have like an interconnect relay between 2 of the motor lead connectors and flip a switch for them to alternate connections to the ESC.
 
J Macker said:
Holy crap! how does he do the maneuver at 1:23-1:25 in the first video?! (hammer-like motion)

And how does he reverse (backup) the plane at 1:36-1:42?

I've never heard or seen of planes backing up like that. of all the ESC's I've used, there's never an option to make the motor spin in reverse. You'd have to have like an interconnect relay between 2 of the motor lead connectors and flip a switch for them to alternate connections to the ESC.
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It's reverse pitch like a heli rotor, the motor doesn't stop and reverse direction.
 
J Macker said:
Holy crap! how does he do the maneuver at 1:23-1:25 in the first video?! (hammer-like motion)

And how does he reverse (backup) the plane at 1:36-1:42?

I've never heard or seen of planes backing up like that. of all the ESC's I've used, there's never an option to make the motor spin in reverse. You'd have to have like an interconnect relay between 2 of the motor lead connectors and flip a switch for them to alternate connections to the ESC.
Click to expand...

Variable-pitch props are the answer you're looking for! Motor keeps spinning the same direction.
 
ah... I'd heard of the variable pitch propellers before, but I thought they were used for quadcopters
 
Yeah that r/c jet was far too large for whatever it was built out of.
 
Is that Balsa wood? Seriously? You need to start milling aluminum at that size, with welding, strut braces, and steel helix coils for bolts liners. How can someone build something that big and not realize that Balsa wouldn't cut it?!?

Maybe he should have flown this instead...and yes that's a F-15 with it's wing missing. And yes it landed safely
airplane-flying-with-one-wing-image10.jpg
 
that is the result of expecting glue to hold at more than 90 psi... the military uses what looks like sheet metal with lag bolts torqued down with air guns or 90 lbs breaker bars to make sure when the air moves over the leading edge it is not hitting the edge of a piece of metal or in their case wood but a single surface. If they understand theromdynamic as well they understood how to follow a model kit instruction they would have understood when that edge came off the way it did it shows exactly what they did wrong at normal speed. You see the cross draft of the different heat from the pavement pushing upward more than the draft over the grass as the leading edge of the wing surface lift off the wing body as if there was no bolts or nuts... which means they used glue to hold a stress point on a wing body while rolling the airframe over a sheering cross draft. my guess if the next time they don't even get a certifaction for any craft that is glued together like popsickle sticks. models are fun but that propellor had to be moving fast enough if the blades decoupled it would have turned that into mess of splinters on the run way... there is an old machine gun that fired tooth picks to make a point and the toothpicks went through a piece of sheet metal... I know metal is more expensive to work with but that was nuts to think it was safe...
 
GotNoRice said:
Damn, what was the plane made out of, Balsa-wood?
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Given that the take-off weight was 100 Kg, I'm going to say yes, it was made of Balsa-wood. The turbine by itself weighed over 40 Kg so that's less than 60 Kg of wood for an 8 meter plane. The German RC community is in some kind of weird competition. Interesting thread here.
 
Jump to 1:30. The plane was rather expensive, built by a team, and the r/c pilot reportedly suffered depression for a while, due to crashing what took forever to build. Pilot error, zigged when he should have zagged.

 
I feel bad when I damage a new RC car body. Seeing these videos confirms I will not be making the jump to aircraft anytime soon.
 
I have had that same failure occur on one of my RC planes back in the day, it was a small one rated for a .20 engine and I put a .45 on it that with a tuned pipe would fly a big Astro Hog nicely. Needless to say on a high speed pass the vertical stabilizer broke off and it crashed but no where near as bad as this plane lol.
 
Bad in he 80s had a bunch of buddies that got into RC plane flying. Looked like a lot of fun and was thinking about getting started in it myself. But within a matter of weeks all of them crashed they planes and quit. Theses were $500-600 RC planes too.
Big money in the 80s.
 
yea that looked way too flimsy to sustain that kind of force for long. Surprised it didnt blow apart on the first turn
 
RC flying is like a concert violin player building his own instrument, then smashing it at the end of the performance. I smashed a shitload of them back in the day, but had a lot of fun as well.

As for balsa wood on a plane this size, it's fine when used in the right place. I'd say the reason for the failure here is for lack of a good attachment for the rudder post and leading edge of the vertical stab - and I wouldn't have used balsa for either of those elements. On a more conventional design, those elements could pass through the fuselage and attach to the top and bottom of the fuse. With the turbine duct there, he tried to attach to the fuse surface.

Here's a 40% aerobatic plane, and it's a wooden structure. Not as big as the jet, but the aerodynamic loads are fairly intense at times. It's hard to get a sense of size, but that plane has a 10ft 6in wingspan (126") and has a 4 cylinder, 200cc engine.

 
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I feel like a large part of the problem with this particular plane was that it is a scale model of the Jas 39 Gripen which was designed to be intentionally unstable.

When you copy the wing locations etc for appearance you are going to get at least some of that inherent instability in the scale model as well.


They did this in order for it to be able to flip out of the way of surface to air missiles and to better be able to dog fight, but this also means that it requires a highly skilled pilot and a sophisticated fly-by-wire system to help keep it in check.

This is why they lost a bunch of the real planes in early exhibitions in the late 80's and early 90's.

The scale model may have gone into an unintentional flip about its axis, resulting in an amount of force on the balsa wood that it just couldn't sustain.
 
A lot has been made about canard-tailless delta wing designs (Eurofighter Typhoon, Dassault Rafale, Saab Gripen) being inherently unstable. (usually as a comparison to American designs) But the reality is they're not any more or less unstable than any other high-performance fighter aircraft. And hobbyists have been flying R/C variants of these aircraft for years.
 
Looks like shitty construction and shortcuts made on a scale that size. Only has himself to blame for that. In my case I lost a custom jet many years ago that was a phenolic and fiber glass build due to some asshat with a Cessna not checking his damn batteries and slamming into me. I've barely flown anything since.
 
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