Ravin Aircraft down in Camperdown - 15 March 2014

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CharlesDavis
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Re: Aircraft down in Camperdown.

Unread post by CharlesDavis » Sun May 04, 2014 4:57 pm

jimdavis wrote:
CharlesDavis wrote:
nrm wrote:Spoke to somebody yesterday intimately involved with Ravin. He told me it was not flutter that caused the problem. Spar was broken due to overload.

Fibres on top of the spar were crushed and those on the bottom were stretched.

Interesting.
Any idea when this "overload" happened ??

It could have been from a high-G pull-up on this flight, or severe turbulence on some previous flight, not so ?
Or a seriously heavy landing.

Jim
One wonders if the under-carriage and mountings would survive an arrival hard enough to damage/break the spar ...?
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Re: Aircraft down in Camperdown.

Unread post by Mike Wissing » Sun May 04, 2014 5:08 pm

This whole spar issue worries me a lot.
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Re: Aircraft down in Camperdown.

Unread post by Aerodon » Mon May 05, 2014 12:16 am

Mike Wissing wrote:This whole spar issue worries me a lot.
Mike,

I agree with you on composite spars - theres a lot that can go wrong in the manufacturing process.

But its back to the issue of the plane being very sensitive in pitch at high speed. All it takes is for a new pilot to apply the control force he is used to in say a Saratoga or C210 at high speed (muscle memory) and then he has overloaded the wing and it fails. In certified aircraft the tail often fails first due to flutter or overload (recent Malibu crash, Bonanza history) followed by pitch down and wings failing in a downward direction.

If the Ravin is very sensitive in pitch and neutrally stable, I surmise that a tail failure could result in a pitch up. If the Ravin's have been released for flight again, there must be more information on hand than just the wings failed due to damage or overload? Any instructions to pilots?

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Re: Aircraft down in Camperdown.

Unread post by nrm » Mon May 05, 2014 6:52 am

Very sensitive in pitch. Very slippery to land, and quite easy to have a hard landing.

Runs away speedwise very quickly if you are not careful.

Definitely not an aircraft for beginners
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Re: Aircraft down in Camperdown.

Unread post by richard C » Mon May 05, 2014 7:30 am

It still doesn't rule out flutter, though, does it ?

The spar could have failed as a result of forces imposed by a catastrophic flutter event, surely ?
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Re: Aircraft down in Camperdown.

Unread post by jimdavis » Mon May 05, 2014 7:57 am

My guess is that this didn't just suddenly happen. It was the final event in a series that possibly started long ago. Possibly a very heavy landing (which will put the same upward bending load on the spar), perhaps combined with some other damage - maybe hangar rash on a control surface that was not balanced properly after repairs, plus the possibility of serious G loads, either at the time or earlier.

I feel sure it is not one single event, or design fault. One has to ask why the aircraft are still allowed to fly if that were the case.

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Re: Aircraft down in Camperdown.

Unread post by richard C » Mon May 05, 2014 8:15 am

I was a shareholder in a fractional ownership scheme. One of the aeries had a prop strike (not ours thank goodness) and was returned to the hanger, minus an inch on each blade, without a murmur. Luckily the next pilot identified the damage in his pre-flight. The previous user was identified and he claimed to have no knowledge of having had a prop-strike. Imagine if the next user had been killed !?

I always used to check the paint was intact on the end of our prop blades after that.
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Re: Aircraft down in Camperdown.

Unread post by StressMerchant » Mon May 05, 2014 1:52 pm

Fibres on top of the spar were crushed and those on the bottom were stretched.
Perhaps not as straightforward as it sounds. One of the characteristics of composites is that the failure modes is not always as simple as they seem. Fibres generally do not 'crush", the resin crushes. In addition to the direct stress, the strength of the resin is also such that complimentary stresses which would be relatively minor for metals will cripple poorly designed composites.
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Re: Aircraft down in Camperdown.

Unread post by Oldlae » Mon May 05, 2014 8:01 pm

I understand from previous posts that the engine and prop "departed" before the impact.
If this is the case then the airframe will pitch up violently, due to the C of G going aft, and this may explain the spar failure.
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Re: Aircraft down in Camperdown.

Unread post by Wingnutter » Tue Oct 13, 2015 10:43 am

Anyone have any further information on this accident?
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Re: Aircraft down in Camperdown.

Unread post by vindog » Tue Oct 13, 2015 12:05 pm

It is common cause that the spar broke. It therefore was over loaded (for that particular spar), that's why it broke. Why was it overloaded? Before the avcom rant starts, I saw this accident happen and assisted in the clean up - lost mates etc...

I agree with Jim and speculate that there were a number of factors contributing to the spar failure and resultant break up. The accident happened at around 15H30 as far as I can recall. Being the 15th of March, it was a hot summer afternoon. I flew in the morning and it was starting to get bumpy on the approach for RW15. So if the DA was up and was getting turbulent, you add a pitchy fast aircraft in the hands of a low hour on type (RIP guys), and then maybe some other contributing factors which gave the result, then the investigation would be headed on the right track. I would like to hear from the guru's the effect of DA on VNE at say 800 ft agl.

What I am asking is say the DA was at 5500ft (elevation is 2430), and VNE is stipulated at say for example at 230 knots, the ASI indicates 220knots and you hit a good bump. What are the actuals that the airframe is subjected to? ( the pilot would think that the speed is ok, not so?)
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Re: Aircraft down in Camperdown.

Unread post by Christo » Tue Oct 13, 2015 12:15 pm

vindog wrote:It is common cause that the spar broke. It therefore was over loaded (for that particular spar), that's why it broke. Why was it overloaded? Before the avcom rant starts, I saw this accident happen and assisted in the clean up - lost mates etc...

I agree with Jim and speculate that there were a number of factors contributing to the spar failure and resultant break up. The accident happened at around 15H30 as far as I can recall. Being the 15th of March, it was a hot summer afternoon. I flew in the morning and it was starting to get bumpy on the approach for RW15. So if the DA was up and was getting turbulent, you add a pitchy fast aircraft in the hands of a low hour on type (RIP guys), and then maybe some other contributing factors which gave the result, then the investigation would be headed on the right track. I would like to hear from the guru's the effect of DA on VNE at say 800 ft agl.

What I am asking is say the DA was at 5500ft (elevation is 2430), and VNE is stipulated at say for example at 230 knots, the ASI indicates 220knots and you hit a good bump. What are the actuals that the airframe is subjected to? ( the pilot would think that the speed is ok, not so?)
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Re: Aircraft down in Camperdown.

Unread post by vindog » Tue Oct 13, 2015 3:23 pm

Thanks Christo, the link supports my question, however remains silent on the issue of turbulence. VNE applies to calm air
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Re: Aircraft down in Camperdown.

Unread post by Mike Wissing » Tue Oct 13, 2015 4:12 pm

That's why you slow down to Va in turbulence. A "good bump" could easily exceed 3.8g, and I assume the airplane in question was operating in the normal category due to the number of people on board.
Why would one be doing 10KIAS under VNE in turbulence anyway?
To start answering your question, ASI readings are not affected by DA. Due to your experienced turbulence factor, vertical wind shear would be more of an issue, so how could you calculate anything without that data?
Clearly the actual g-load exceeded the airframe limitations.
BTW: I learned to fly in PMB, so have many hours flying in Camperdown and know that it can get rather bumpy very quickly.
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Re: Aircraft down in Camperdown.

Unread post by Volo » Tue Oct 13, 2015 4:43 pm

From what I have read and understood about this aircraft , I would put my money on over control / PIO .
Very easy to do at or near VNE in turbulence and even if an experienced hand is sitting in the other seat , his / her intervention would be too late .

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