Whilst I am in no position to comment on KR-2 handling qualities, the 'test pilot' data collection nerd that I am can't help using Colin's information to quantify his short field landing in Iceland, given that the wind was 'calm' so that's a nuisance variable that can be ignored.
Touching down at 33.5m/s and decelerating over 16s is an acceleration of -2.1m/s^2 results in a landing distance of (33.5)*(16)-(0.5)*(2.1)*(16)^2 or 267m or 876ft - pretty close to Colin's estimate. Clearly this is a ground roll distance at 'whatever' mass on grass - the distance over a 50' obstacle would be considerably more. Put another way, Colin's brakes are capable of 'decelerating' his aircraft after touchdown on short grass at (-2.1)*(2.24) = -4.7 mph per second of ground roll at whatever the Iceland landing mass was. This is useful information. What if Colin had touched down at 85mph? Making the assumption that his brakes retained the same average effectiveness then time to a stop would have been (38)/(2.1) = 18.1s. The resulting distance to a stop would have been (38)*(18.1) - (0.5)*(2.1)*(18.1)^2 = 344m or 1129 ft. Still safe from the lava flow - but by a considerably reduced margin. The point that I am trying to make is that the collection of a few simple data points allows you to 'flesh out' some numbers that describe the take-off and landing distance of your homebuilt and enables you to make an educated decision as to whether you can take-off or land on a given strip ... as opposed to sucking your teeth and ending up in a hedge. Kiwi ________________________________ From: KRnet <krnet-boun...@list.krnet.org> on behalf of colin hales via KRnet <krnet@list.krnet.org> Sent: Monday, 26 September 2022 23:31 To: krnet@list.krnet.org <krnet@list.krnet.org> Cc: colin hales <colinha...@hotmail.com> Subject: KRnet> Landing and full back stick times. If I land gently and then hit the brakes hard, I sometimes need full back stick almost immediately to balance the forward rotation around the axles due to the braking effect. It depends how good your brakes are and the runway condition. As the speed decreases, the main lifting effect of the centre of lift created by the wings behind the axles drops off and you can hit the brakes harder. If you would like to watch this video, https://www.youtube.com/watch?v=9FJuTyf2sJc one of the shortest landings I've done, touch down speed about 75 mph around 2:42 in the video, tail down against full brakes and full back stick 7 seconds later coming to a halt or turning off speed at 2,58 so that is 16 seconds after touch down. Landing distance was about 300 meters 900 feet on a 500 meter 1500 feet grass strip with a Lava flow bank at the end of it in Iceland, so there was no run off it if all went a bit wrong... Unfortunately, it was a still day with no head wind, as that helps a lot obviously. On touchdown, sometimes I need to push forward on the stick to stop the rotation from a hard landing where the tail continues to descend after the mains have touched first, increasing the angle of attack and lifting the aircraft off the ground again which then creates a bounce, but a touch of brakes on touchdown also helps that, then it's just a balancing act to ride it on the mainwheels so you can see over the nose until full forward stick and brakes won't keep the tail up any more and then when the tail wheel touches at that speed about 35 mph, do what you like with the elevator, it won't effect the aircraft as the airspeed is too low. I don't know if you have ever sat two people in a KR2 and tried to lift the tail. It's about 200 lbs of weight on there, so no chance of it nosing over while taxing so I only hold the elevator neutral to stop it bouncing around. If it's slowing down you want to do Mike, your brakes will work far better than holding the stick back to create more drag with your tail wheel. Hope this answers your question. CH.
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