Light aircraft down Pretoria, ZS-UKU KR2

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Re: Light aircraft down Pretoria.

Unread post by flypiper » Sun Oct 31, 2021 10:12 am

Morning,
Heard that the wing was found away ftom the remains can somebody get a picture of it and that will stop our speculation,
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Re: Light aircraft down Pretoria.

Unread post by crazydoc » Sun Oct 31, 2021 12:39 pm

Heard from reliable source that spar broke right in middle under seat
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Re: Light aircraft down Pretoria.

Unread post by Rudix » Sun Oct 31, 2021 3:27 pm

crazydoc wrote:
Sun Oct 31, 2021 12:39 pm
Heard from reliable source that spar broke right in middle under seat
Yes, that is similar to what I heard!
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Re: Light aircraft down Pretoria.

Unread post by tbone » Sun Oct 31, 2021 5:57 pm

Blue skies Neville…

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...‘sauvage de la journée’...

...'LOSS OF SEPARATION WITH TERRAIN'....
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Re: Light aircraft down Pretoria.

Unread post by TxT » 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.
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Re: Light aircraft down Pretoria.

Unread post by SandPiper » Sun Oct 31, 2021 9:54 pm

http://www.n56ml.com/swings.html

Browse thru the rest of the site, lots of info on the KR2.
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Re: Light aircraft down Pretoria.

Unread post by Volo » Sun Oct 31, 2021 10:37 pm

The rather detailed discussion by this pilot on his experience with a KR2 and his note about severe stress from PIOs may be a clue to spar failure.
.........
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KR2 KR2s Plans

 Thread starterNev25  Start dateDec 2, 2013

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Nev25Well-Known Member

Dec 2, 2013

#1

Wondering if anyone has a set of KR2 KR2s Plans they want to sell

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bmcjWell-Known Member 

HBA Supporter

Dec 2, 2013

#2

KR-2, huh? In my mind, the question would be "How much is anyone willing to pay for me to take the plans off their hands?" :gig:

Head in the cloudsWell-Known Member

Dec 2, 2013

#3

Yes Bruce, I recall posting on HBA some while back about my opinion of the KR2. I helped build one in Victoria in the mid 1980s and moved to Queensland just before it first flew. The next year I travelled down that way again for our mini-Oshkosh at Mangalore and had a chance to go for a fly in the KR2. I can still say that of the 50-60 different types I've flown, the KR2 was the most horrible by a very long way. It was such a shame to have put so much work into building what turned out to be such a horrendous (and dangerous) design. IMHO.

EDIT - I flew quite a number of hours in an Osprey 2 a few years later, now I'm wondering which was worse 

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N

Nev25Well-Known Member

Dec 3, 2013

#4

WOW what's the problem with it
Everyone I have spoken too up to now have raved how got it is?

For me it tick more boxes than any other for a scratch build

T

TFFWell-Known Member

Dec 3, 2013

#5

Its a hot flying airframe with not enough power. Many of the old homebuilts are not low time pilot friendly. Its a fat short canoe with wings. Slimmed down into a single seater makes it a better plane; the designer was something like 5-5 130 lbs.

SpainCubWell-Known Member

Dec 3, 2013

#6

I flew one, after many hours of taxing just to get a feeling of the rascal on the ground, I have my opinions on the plane of only two hours of flight testing it, but it never grew on me. Heads in the Clouds, what's your take on the flying characteristics? What made it so dangerous for you?

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dcstrngWell-Known Member

Dec 3, 2013

#7

Nev25 said:

WOW what's the problem with it

KRs, like many smallish birds, have had a reputation for being control sensitive or worse -- but then the early Bonanzas were know as “doctor killers,” so no aircraft is immune … in many cases the folks who should be flying KRs should be higher-time craftsmen with current skills and a addiction to scrupulous workmanship.—remember this is a bird that bumps up against Glasair and Lancair speeds, and pilot demands.

The reality is that what attracts many of us to these birds are inexpensive plans, purportedly less-challenging/forgiving construction and allegedly cheap cost… What gets folks into trouble in my observation, is they forget that they are building an aerial hotrod that can go quite fast on small power, but can get the unwary into trouble just as speedily. So occasionally we end up with a variation on the student pilots with immature shop skills scenario, working on pure adrenalin and high-hopes of getting their budget-bird in the air… good intentions, potentially ugly combination.

Which is not to say the KR hasn’t had its quirks – but most have been refined out over the decades and now it is a pretty mature design for those qualified. I’ve carried KR2/2S plans around for a couple of decades – never built it, but not because I thought there was anything wrong with the bird; to the contrary it is an exceptionally friendly bird – one might hang out on krnet.org and read the success stories. But, those success stories were built and flown by folks who respected it as an aerial hotrod…

With careful budgeting, scrounging and discipline (and a little luck) it is not unrealistic to build a KR for around the cost of a good 103 bird, but it ain’t one, that is for sure…

Mark's site: Mark Langford's KR2S great site and (now) a very experienced KR flyer -- but he's good about telling both the good and the bad...

Head in the cloudsWell-Known Member

Dec 3, 2013

#8

SpainCub said:

Heads in the Clouds, what's your take on the flying characteristics? What made it so dangerous for you?

Nev25 said:

WOW what's the problem with it

I only ever flew that one, so I can't comment about others and the ones with later mods.

The fella who owned the one we built was, very fortunately, also a moderately experienced helicopter pilot and he believed that having flown other very sensitive machines was the only thing that saved him on the first flight during which he got into all sorts of strife.

When we went for a fly together he deliberately didn't tell me much about the handling characteristics. He was interested in finding out what the little bird could do and I was reputed as a more experienced plane pilot than he was at the time. More experienced in small and sensitive craft that is, and I had a bit of aeros training and used to enjoy throwing planes around a bit.

Anyway, the owner did the take-off and climb, retracted the gear, and handed over to me at top of climb. We instantly went into violent pilot induced oscillations (PIOs) crushed into the seat one moment and pressed against the canopy the next. The owner took over and quickly smoothed it out again. I spent the rest of that flight and the next couple just learning to fly it straight and level, no excessive manoeuvres in that one for me, and have never had a desire to sit in a KR again, and never will.

Apart from being well versed in sensitive machines (the helicopters) what saved the owner was that he was a very tall man and so was able to brace his wrist against his knee to stabilise the stick, any attempt to fly the thing just holding the stick was virtually impossible, at least not until you might know the thing well and I had no interest in getting intimate with it. The action of swinging the lever to raise and lower the gear caused a PIO that seemed almost enough to rip the wings off.

This one had a Revmaster engine and the climb was nothing to write home about but it easily did 140kts or so in the cruise, so all of dcstrng's comments about underpowered but a hotrod nonetheless are very accurate.

The latter flights I did at the time also showed the thing to be negatively stable (unstable) at times even though it had a forward CG. Hands off and it would either zoom or bunt at higher speeds and holding off too much during the landing resulted in it pitching up uncommanded, requiring a very quick correction or you could end up stalled at five feet.

I've been told that some of the later stretched and modified tail versions (with fixed HS) are more kindly but even though in some circles I might be described as a higher time rather than lower time pilot I wouldn't go near one again. On the other hand there is one fella near where I live who has one and loves it. He's a larger gent and treats it as a strictly single seater and seems to spend more time in the air than on the ground, so you need to get others' opinions too, I might just be once bitten, twice shy.

T

TFFWell-Known Member

Dec 3, 2013

#9

I believe the sensitive controls seems to be a 60's homebuilt thing. Tailwinds, T2s, and some others are touchy. The Tailwind because Steve Wittman wanted to fly with finger pressure because there were no auto pilots for small planes. The actual control authority is only about as fast as a C150

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TopazSuper Moderator 

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Log Member

Dec 3, 2013

#10

TFF said:

I believe the sensitive controls seems to be a 60's homebuilt thing. Tailwinds, T2s, and some others are touchy. The Tailwind because Steve Wittman wanted to fly with finger pressure because there were no auto pilots for small planes. The actual control authority is only about as fast as a C150

Very common for homebuilts of the '60's and '70's. Not ubiquitous, mind you - some of the aircraft of the time were quite pleasant to fly - but the higher-performing aircraft tended to skimp on tail area quite a bit, to the detriment of stability and control.

N

Nev25Well-Known Member

Dec 3, 2013

#11

bmcj said:

KR-2, huh? In my mind, the question would be "How much is anyone willing to pay for me to take the plans off their hands?" :gig:

Well if anyone giving them away I'm excepting
But am willing to buy

PopsWell-Known Member 

HBA Supporter

 

Log Member

Dec 3, 2013

#12

I built a KR-2 in 1975 and just had to finish the painting and sold it. Glad I did. Bought a Falconar F-12 project and finished it and flew it 5 years. Wife and I did a lot of traveling in the F-12 and that would not have happen in the KR-2. The F-12 was a so, so much better airplane for what we wanted to do. Dan

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Re: Light aircraft down Pretoria.

Unread post by TxT » Mon Nov 01, 2021 11:16 am

SandPiper wrote:
Sun Oct 31, 2021 9:54 pm
http://www.n56ml.com/swings.html

Browse thru the rest of the site, lots of info on the KR2.
Thanks. Much appreciated. Fascinating reading.
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Re: Light aircraft down Pretoria.

Unread post by spatz » Mon Nov 01, 2021 11:27 am

Volo wrote:
Sun Oct 31, 2021 10:37 pm
The rather detailed discussion by this pilot on his experience with a KR2 and his note about severe stress from PIOs may be a clue to spar failure.
.........
snipped
Dave i seem to recall people saying the same about the Std Cirrus back in the day with its all flying Tail plane, basically people went from machines that required effort to fly to slippery designs then blamed the aircraft for being too unstable as they were overcontrolling all the time.
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Re: Light aircraft down Pretoria.

Unread post by SandPiper » Mon Nov 01, 2021 11:36 am

Another hi-jack:

Attached some more info re. the KR´s handling and design.
KR2 A Critical Analysis.pdf
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Re: Light aircraft down Pretoria.

Unread post by Russell Phillips » Mon Nov 01, 2021 2:02 pm

KR ailerons MUST be 100% mass balanced. This is particularly important to check if paint is ever added to the aileron.

Unlike in some of the gliders in the video it is unlikely that aileron flutter in a KR can be arrested after it starts and the wing experiences massive alternating positive and negative g loads in just a few seconds.
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Re: Light aircraft down Pretoria.

Unread post by Volo » Mon Nov 01, 2021 2:08 pm

spatz wrote:
Mon Nov 01, 2021 11:27 am
Volo wrote:
Sun Oct 31, 2021 10:37 pm
The rather detailed discussion by this pilot on his experience with a KR2 and his note about severe stress from PIOs may be a clue to spar failure.
.........
snipped
Dave i seem to recall people saying the same about the Std Cirrus back in the day with its all flying Tail plane, basically people went from machines that required effort to fly to slippery designs then blamed the aircraft for being too unstable as they were overcontrolling all the time.
Keven
..........
Keven - I so remember the sensitivety of both the Cirrus and Tims Nimbus 2 which i flew at Thabazimbi - some PIOs nearly had me diving in to the bush while on tow!!
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Re: Light aircraft down Pretoria.

Unread post by Jean Crous » Mon Nov 01, 2021 2:17 pm

Do I understand correctly that the accident happened in the turn from base to final ? If so at what estimated speed would this have been ? 100mph ? Does flutter not happen at higher speeds ? Can flutter happen when the ailerons are loaded in a bank ?
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Re: Light aircraft down Pretoria.

Unread post by ACE MAN » Mon Nov 01, 2021 3:15 pm

Russell Phillips wrote:
Mon Nov 01, 2021 2:02 pm
KR ailerons MUST be 100% mass balanced. This is particularly important to check if paint is ever added to the aileron.

Unlike in some of the gliders in the video it is unlikely that aileron flutter in a KR can be arrested after it starts and the wing experiences massive alternating positive and negative g loads in just a few seconds.
The last two minutes makes for interesting listening.
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Re: Light aircraft down Pretoria.

Unread post by Russell Phillips » Mon Nov 01, 2021 3:19 pm

Jean Crous wrote:
Mon Nov 01, 2021 2:17 pm
Do I understand correctly that the accident happened in the turn from base to final ? If so at what estimated speed would this have been ? 100mph ? Does flutter not happen at higher speeds ? Can flutter happen when the ailerons are loaded in a bank ?
Jean
Can happen at any speed but becomes exponentially more destructive at higher speeds. And yes it needs some excitation to get it going. A brisk control input for example.
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