What the Heck Wednesday - Mid-flight Catastrophe

In this weeks installment of What the Heck Wednesday I present you this amazing half scale SAAB GRIPEN XXXL video.

Splash

What the Heck Happened?

In this weeks installment of What the Heck Wednesday I present you this amazing half scale SAAB GRIPEN XXXL video. You may have already seen this video as it was posted in 2016 and has over 28 Million views. The size and scale of this model is staggering at 8M long and weighing 100KG! It's just massive and that word also applies to the cost and effort it took to create.

The model is turbine powered and the take off and first few minutes of the flight go according to plan. Once the gear is retracted he started running through some basic aerobatic maneuvers and the rolls looked great. Then it all went pear shaped during a show pass with a roll to possibly a knife edge pass. The vertical stabilizer shreds under load and culminates with the rest of the plane looking like it went through a blender. Debris rains down and I'm sure the pilot, crew and crowd were all in shock. So what the heck happened? Not enough structural support? What would cause the plane to explode like that after the vertical was gone? This should be an interesting discussion. Let's hear your thoughts in the comments below.

Thread Tools
Sep 30, 2020, 08:32 AM
Registered User
I would like to know the real total cost of that plane... I remember looking up the turbine, and I think it alone was like $25k.

I have no clue about building planes like that, but it seems to me guys try to build things too light sometimes... A plane that big should probably have been much stronger structurally, and therefore probably heavier.. I thought it looked like it flew too light...(bit blimpy..)
Sep 30, 2020, 09:04 AM
Design Engineer
i agree with Herrsavage. the weight and size of that plane must have been too much for the structural points of the stabilizing surfaces.
I watched the destruction a few times at .25x speed (thanks youtube) and noticed a few things. As they roll into the knife edge at 1:49, you see the tail fold over, away from the ground. I believe there was too much force acting on that tail as the plane was trying to keep in the knife edge. Jets require a TON of lifting and control authority on the vertical stab when doing a knife edge. and if you watch jets (or any other plane) do knife edges, they are never parallel with the ground. they are always a little nose up. With this jet, the tail just didn't have the strength to hold together under all that force.
The resulting crash was just the after affects of loosing the vertical stab. you see the jet roll to a more nose up position as the tail can no longer control the yaw. the wind then gets under the wings rolling it so that all force of the wind is pushing almost perpendicular to the face of the wings and forward fins, thus destroying them under all the pressure.
The nose comes off probably because of some structural member of the front fins destroying some of the framework when they came off.

Part of me wonders if they went into that final knife edge too slow. for being a jet, that thing was just crawling its way thru the sky. kinda sluggish.
All in all, i think it was not built strong enough to handle the weights and forces of the whole assembly.
Sep 30, 2020, 10:10 AM
B for Bruce
BMatthews's Avatar
From the way the fin failed and the way that the rest of it broke up it would appear that the structure was simply not given the proper sort of thought and built for the loads that would be encountered. And this is compounded by the fact that the model wasn't even flying all that fast when the failure occurred that further supports the idea that there simply wasn't enough materials used in the proper way.

I did notice in the video a lot of white core. So I'll assume that the primary structure was epoxy and fiberglass over foam. A good number of smaller experimental airplanes have been built this way. And at the size of that Grippen I'm thinking that less thought of model sized methods and more of the layups and options used by such planes as the Vari-Eze and Quickie should have been employed.

But without more details of the Grippen's structure it's impossible to do more than suggest something along that line.

Either way it was a shame to see all that work come to pieces like that.
Sep 30, 2020, 10:34 AM
Registered User
Maybe the turbine just had X-power, so they had to figure out Y-weight given Z-size?..

I.e. it needed to be even more powerful, but also more solidly built and heavier to handle the strain.

What was it I read once about dinosaur bones having to have so much more mass, not just linearly but proportionately, as they got bigger and bigger?...
Sep 30, 2020, 12:54 PM
Registered User
Angelo's Avatar
"...of course, it's with an aviation certificate..."

Makes me wonder just what that certificate covers. I agree with the consensus, it was just horribly under built. How do you make such a massive and expensive project, and not engineer it properly?
Sep 30, 2020, 02:06 PM
Registered User
I hope he's got a garbage bag under the front seat of his car!
Sep 30, 2020, 03:24 PM
I'd rather be Flying
davecee's Avatar
https://www.rcgroups.com/forums/show...5&postcount=18
Looks like a wood (balsa and ply?) constructed airplane, judging by the debris and a glimpse of the interior as it fell. Material selection and construction techniques apparently better suited for a much smaller and lighter plane. I did like the slow flight before the breakup though.
Sep 30, 2020, 03:58 PM
AMA 986339 FCC KB5LAM/4
davidterrell80's Avatar
It looks like as the pilot eased into knife edge at 1:48 and you see the rudder deflect to the left to hold the nose up. Just after 1:49 you see the fin deflect to the left and fail. Very odd.
Sep 30, 2020, 07:53 PM
Registered User
earlwb's Avatar
yes I agree, the owner built it too light and wound up with structural faults being it was going to fail, you just don't know when. It may have been OK for a while longer if he avoided knife edge flying or using the rudder much in the air.

When I think about it, some years ago there were a lot of ARF fiberglass fuselage turbo-jets having the tail fins fail on them too. But they were going blindly fast when the tails let go. I remember a bunch of guys being upset over it at the time.
Latest blog entry: yes I still fly airplanes too
Oct 01, 2020, 01:38 AM
DFS#000178
Rampage's Avatar
The best thing about this video was how the owner (?) looked to be having a severe emotional crisis and the pilot was just like "Well...oops?"
Oct 01, 2020, 03:00 AM
Electric Coolhunter
Thomas B's Avatar
That one was never a mystery. Underbuilt and overstressed.
Oct 01, 2020, 03:15 AM
Registered User
Yep, I thought that the first time I saw it..

Am I on the right track though in thinking maybe they built around the given power of the turbine and according to a desired size, and that for the plane to be that size it would have to be much heavier, and therefore have to have an even more powerful turbine?
Oct 01, 2020, 08:13 PM
WJH
WJH
B777F Captain
WJH's Avatar
Built like an Airbus
Oct 01, 2020, 09:49 PM
Registered User
Angelo's Avatar
Quote:
Originally Posted by WJH
Built like an Airbus
Now there's some dark humor!


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Article What the Heck Wednesday - RC Warbird Crash Jason Cole Electric Warbirds 12 Oct 08, 2020 08:09 PM
Article What the Heck Wednesday - RC Gas Trainer Crash Jason Cole Fuel Plane Talk 56 Oct 08, 2020 04:53 PM
Article What the Heck Wednesday - RC Helicopter Crash Jason Cole Electric Heli Talk 26 Sep 15, 2020 09:43 AM
Article What the Heck Wednesday - RC Jet Crash Jason Cole Fuel Jet Talk 31 Sep 13, 2020 06:26 PM