Light aircraft down Pretoria, ZS-UKU KR2

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Re: Light aircraft down Pretoria.

Unread post by Volo » Mon Nov 01, 2021 8:22 pm

From all that I have read and seen and the history of the KR2 It rather looks like flutter is the culprit here .
I think Russel hinted at it with his general comments on flutter.
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Re: Light aircraft down Pretoria.

Unread post by cage » Mon Nov 01, 2021 8:36 pm

Golf Tango wrote:
Mon Nov 01, 2021 3:34 pm
We were flipping some Pretoria Boys High boys the previous Friday at Kittyhawk. The gentleman killed in this accident was one of the pilots there, although he didn't flip any of them, he was flying the accident plane there. There was a thanks ceremony after and in the back ground the the deceased was doing all kinds of aerobatics in the KR2. Most of the guys (high time aerobatics pilots mostly) were amazed with how he was flying that plane as was I. Means we had never seen a KR2 flown like that 😱. I remarked to my colleagues that the airframe whistled nicely. Shame.
From my brief crossing of paths with the deceased, he seemed to embody that saying about old and bold pilots.
While many will be shocked, I suspect there will be plenty of people unsurprised that it ended this way.
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Re: Light aircraft down Pretoria.

Unread post by tbone » Mon Nov 01, 2021 9:33 pm

cage wrote:
Mon Nov 01, 2021 8:36 pm
Golf Tango wrote:
Mon Nov 01, 2021 3:34 pm
We were flipping some Pretoria Boys High boys the previous Friday at Kittyhawk. The gentleman killed in this accident was one of the pilots there, although he didn't flip any of them, he was flying the accident plane there. There was a thanks ceremony after and in the back ground the the deceased was doing all kinds of aerobatics in the KR2. Most of the guys (high time aerobatics pilots mostly) were amazed with how he was flying that plane as was I. Means we had never seen a KR2 flown like that 😱. I remarked to my colleagues that the airframe whistled nicely. Shame.
From my brief crossing of paths with the deceased, he seemed to embody that saying about old and bold pilots.
While many will be shocked, I suspect there will be plenty of people unsurprised that it ended this way.
A lot of experienced guys end up here… and unfortunately, everyone but the pilot saw it comming…

B.
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Re: Light aircraft down Pretoria.

Unread post by PapaD » Thu Nov 04, 2021 9:47 am

Memorial.jpg
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Re: Light aircraft down Pretoria.

Unread post by milegrin » Sun Nov 07, 2021 10:11 am

TxT wrote:
Sun Oct 31, 2021 9:01 pm
It would be great if one of the KR2 constructors could post the centre section drawing or schematic.
Drawing from my build manual
kr2_center_spar-drawing12.jpg
No polystyrene or foam inside the spar.

There has been a huge amount of unsubstantiated speculation in this thread; may I suggest we wait for a more complete and preferably official report of the cause? Not only so we can learn from fact and not supposition but also out of respect from Neville, Dicky and their families.
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Re: Light aircraft down Pretoria.

Unread post by Whirly » Sun Nov 07, 2021 10:35 am

Speculation is encouraged in this section. I have actually read very little "wild" speculations in this thread.

Whirly.
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Re: Light aircraft down Pretoria.

Unread post by Theuns v V » Sun Nov 07, 2021 11:00 am

If we look at the design of that wood spar its a box beam. The bending loads will be taken up by the top and bottom spar caps. Lets say it is a cantilever wing as per the KR and it is under positive G, the top cap wll be in compressive load and the bottom cap in tensile loads. The short little upright sections is there for 2 reasons, the first is to help keep the two caps appart under load and the second is to help stiffen the vertical grain ply wood shearwebs.

The shear webs are mostly there to bind the two caps into a single beam and stop the caps from moving in opposite directions wrt each other when a bending load is applied to it.

Usually designers tend to taper the caps off towards the tips as the loads become less from the root to the tip section. With those little upright sections between the spar caps there should be no need to have any foam in the spars.

The interesting question will be to see what the actual glue integrity is of the cap to shearweb joints if there is anything left to study
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Re: Light aircraft down Pretoria.

Unread post by Sideslip » Sun Nov 07, 2021 11:21 am

There was a suggestion further back in the thread that it all went pear shaped in the turn from base to final.

Can anyone confirm this?

And if so, was the aircraft flying a standard/normal/calm circuit or was the aircraft still being subject to heavy handling/airobatics at that stage?
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Re: Light aircraft down Pretoria.

Unread post by GeraldNagel » Sun Nov 07, 2021 11:49 am

Interesting reading. Newsletters.

http://www.krnet.org/newsletter/nl6.pdf
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Re: Light aircraft down Pretoria.

Unread post by mi'cmaq » Sun Nov 07, 2021 12:02 pm

If I was involved in the accident investigation the first thing I would look at was the glue integrity at the joints

There was a wooden Robin aircraft at Phesantekraal Airport that had a wing fail just after takeoff and made a miraculous safe landing back to the airport due to the skill and cool headed handling by the owner/pilot - The glue joints failed and this was a factory built certified aircraft ! Apparently the factory either let quality control slip or it was a bad batch of glue

I was flying gliders out of L'Ancienne-Lorette Airport (now Quebec City intl YQB) - The Tiger Moth tug came up for recover and when we stripped the fabric off the wings we were shocked to discover the casien glue had deteriorated to the point where you could just pull the glued wooden pieces of the wing apart with little effort

The condition of fabric is easy to determine ; corrosion is visible (with the possible exception of intergranular corrosion) - but glue and old aeroplanes requires exceptional investigation to maintain airworthiness
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Re: Light aircraft down Pretoria.

Unread post by Theuns v V » Sun Nov 07, 2021 5:29 pm

Old types of glues are not necessarily bad, i rebuilt a tiger moth wing some years back and most of it was still in good nick, same with a stearman i worked on. Now for a 1942 airplane i was pleasantly surprised.

It is just that the older glues are not so forgiving like modern epoxy glues. Even using epoxy on aircraft structures i make a couple of break blocks to test the mix when cured, if i vave anwood and not joint failure i know it will be safe
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Re: Light aircraft down Pretoria.

Unread post by GeraldNagel » Sun Nov 07, 2021 10:49 pm

I worked on my own Boeing Stearman when the spar broke. This was done under the supervision of well known experts on Rand at the time.

It was a hell of a job to remove the glued ribs from the section that required the new section of spar. Those little nails with glue on the head was tight as.......

I therefor agree, age of glue does in most instances does not weaken. Moisture, wrong material and excessive force, above what it was designed for, will or may result in failure. My opinion.
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Re: Light aircraft down Pretoria.

Unread post by GeraldNagel » Sun Nov 07, 2021 10:59 pm

Testing of a spar on a weathered KR2. Look where it started to show damage first.
> As for spar tests, please take a look at the 2008 KR Gathering website
> at http://www.krnet.org/mvn2008/ , about a third of the way down, for a
> spar test conducted at the 2008 Gathering. Look how perversely bent the
> inner and outer spars are bent before failure. As a data point, KR
> wings don't visibly flex when flying in moderate turbulence. I can't
> imagine what you have to do while flying to bend them (or their
> fittings) enough to fail....other than impacting the ground at high speed!
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Re: Light aircraft down Pretoria.

Unread post by GeraldNagel » Sun Nov 07, 2021 11:00 pm

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Re: Light aircraft down Pretoria.

Unread post by PapaD » Mon Nov 08, 2021 6:17 am

Neville Henri Ferreira Memorial Live Streaming:

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