Hi Stef,

One issue to resolve for yourself before aerobatics in your KR would be spins.  

There have been discussions about un-recoverable spins in the KR.   I’m not 
sure they are well informed, or just fears of the monster under the bed.  
However there have been a couple of tragic incidents 
(https://www.flyingmag.com/technique/accidents/aftermath-his-last-selfie 
<https://www.flyingmag.com/technique/accidents/aftermath-his-last-selfie>) 
(http://www.kathrynsreport.com/2013/08/kr-2-plane-crash-near-cataldo-idaho.html 
<http://www.kathrynsreport.com/2013/08/kr-2-plane-crash-near-cataldo-idaho.html>),
 so that monster has to be taken seriously till someone takes a peek.

"Essentially, the first part of the flight was uneventful with the pilot 
performing some turns and steep banked maneuvers. Upon reaching the 
geographical area where the accident occurred, the pilot initiated an 
intentional spin, throttling the engine to idle, pulling on the carburetor 
heat, and increasing the nose up attitude of the airplane until it stalled and 
entered a spin to the left. During the first few rotations the engine quit, and 
the propeller stopped turning. After several rotations the spin stabilized 
about 20 degrees nose down, and remained in the steady state until impact. 
During the descent the pilot was observed attempting various control inputs 
without effect."

It is important to note that unrecoverable spins can happen in almost any 
airplane:
https://www.flyingmag.com/safety/accident-investigations/unrecoverable-spins 
<https://www.flyingmag.com/safety/accident-investigations/unrecoverable-spins>

"PARE (not CIGAR, ARROW or GUMP) summarizes the proper actions for spin 
recovery. Power to idle. Ailerons neutral. Rudder hard against the spin. 
Elevator sharply nose-down (or nose-up for an inverted spin)."

This is from the design analysis of the KR 
(http://kr2seafury.com/resources/1988_01_05.pdf 
<http://kr2seafury.com/resources/1988_01_05.pdf>):

"He believes that going to the aft end of this en- velope will guarantee an 
unstable KR. Worse, in a departure or approach stall situation, a flat spin is 
likely to quickly develop and recovery would not be easy if even possible. 
Piper experienced this on the Cherokee 140. There have been cases where the 140 
has gone into an unrecoverable stall-spin with the loading close to but still 
within the aft CG limit. In the author's opinion, the KR design is very similar 
to the classical Cherokee, except for the stabilator.
The author would never purposely spin his KR, but will, by the same token, 
never load the plane such that the final loaded CG is further aft than 2 inches 
to the rear of the main spar aft surface. It has been tried beyond there and 
the re- sults are not pleasant. Wallowing, undulating and general instability 
show up back there.

The answer? Consider defining the CG envelope as being only 6 inches long, and 
drop off the last two inches of the advertised envelope."  


If you search KRnet for “spins" 
(https://www.mail-archive.com/search?q=spins&l=krnet%40list.krnet.org 
<https://www.mail-archive.com/search?q=spins&l=krnet@list.krnet.org>)  you will 
find a lot of discussion.  Importantly, some with direct experience say the KR 
performs and recovers perfectly well in spins.  

The take home lesson:  If you are going to do aerobatics, make sure your plane 
is loaded for a forward CG, that you start your exploration of the envelopes 
with lots of altitude, and if it were me, I’d have a parachute (which are 
required here for aerobatics) 
(https://airfactsjournal.com/2016/06/aerobatics-need-parachute/).  

Cheers,
Owen


> On Oct 12, 2018, at 9:00 AM, krnet-requ...@list.krnet.org wrote:
> 
> Message: 4
> Date: Fri, 12 Oct 2018 12:20:45 +0200 (CEST)
> From: Stef den Boer <stefk...@ziggo.nl <mailto:stefk...@ziggo.nl>>
> To: KRnet <krnet@list.krnet.org <mailto:krnet@list.krnet.org>>
> Subject: KR> Aerobatics
> Message-ID: <1599605761.105457.1539339645...@mail.ziggo.nl 
> <mailto:1599605761.105457.1539339645...@mail.ziggo.nl>>
> Content-Type: text/plain; charset=UTF-8
> 
> Hi,
> 
> Bussy to finalize the paperwork and my pilot operating handbook.
> 
> I know we there is a lot spoken about aerobatics, but is there a official 
> document thats approve the light aerobatics?
> 
> 
> Stef 
> 
> 
> 
> Steph and his dad are building the KR-2S see 
> http://www.masttotaalconcept.nl/kr2 
> <http://www.masttotaalconcept.nl/kr2>http://www.masttotaalconcept.nl/kr2 
> <http://www.masttotaalconcept.nl/kr2>

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