It is scary to think about. It is beyond scary when it actually happens. In a plane that has no pre-warnings it can be deadly. Keep in mind here that I am not saying that anyone should go out there willy nilly seeing what their flutter speed is. The KR should be fine up to the 200 MPH design speed if built properly and if the ailerons are ballanced properly. If you are going to fly your plane some day over houses or with passengers at 200 then you need to test up to that speed during your initial testing. That is the FAAs rule, not mine. When you test to that speed you need to do it correctly to make sure that you have not just accelerated through your flutter speed like I did.
If you want to fly over 200 you are on uncharted ground. If the idea of doing proper flutter testing scares you than you should not fly there. Flying at speeds that you have not done proper testing at should scare you a lot more than proper flutter testing. If you just have to put your Vne at 250 fine. Borrow a chute and test correctly at altitude. If you do get flutter you want to do three things simultaneously. Pull the throttle to idle, pull back on the stick, and roll into a turn. Pulling the throttle and pulling back on the stick is to reduce speed as fast as you can. Pulling back on the stick is also to load the wings. Pull a few G. I understand that will help to stop the flutter. The wings producing a lot of lift, the Gs pulling against it, and the change in angle of attack upset the forces that continue the flutter from what I understand. Pulling a few Gs also is the fastest way to decrease your speed. Rolling into a turn is to load the ailerons. When you are just straight and level they are free to flutter. Rolling into a turn puts air pressure on one side of the aileron and the control system forces into play. This takes out the play and flex in the system, changes the dampening, and should stop the flutter. Here is a copy of another post from Bud Davisson. When I was doing my testing my stick would quickly return to center with no overshoot that I could see. It was very obvious as I got near flutter speed because the response was noticibly different. It felt different and would overhsoot and return then. Copy follows: If you're just getting a buzz but it's not building to flutter, it's not great but it's not flutter either. The slap and wait thing works at any speed and shouldn't be feared. If you're getting a quick return to center, it's heavily damped, which is good. So, it'll be easy to see when that is changing: it will either go back to center more slowly or will overshoot slightly. You're just looking for a change. Also, I forgot an important part of the procedure: what do you do, if you get it, but it appears everyone knows that. Change the conditions on all three axis, which is nothing more than power back, pitch up to get G and decell, roll into turn, all at one time. Don't forget that increasing structural strength doesn't eliminate flutter, it just moves it to another point. Ditto for deflexing or reflexing ailerons. This conversation has gone too far without an engineer from Mustang Aero chiming in. The rest of us are just shooting from the hip, but they should have concrete input to share and this is a serious subject. bd Brian Kraut Engineering Alternatives, Inc. www.engalt.com -----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On Behalf Of Dan Heath Sent: Saturday, December 23, 2006 10:14 PM To: kr...@mylist.net Subject: Re: KR> Flutter Testing OK, so what do you do if you actually get flutter, when testing. Scary. See N64KR at http://KRBuilder.org - Then click on the pics See you at the 2007 - KR Gathering There is a time for building and a time for FLYING and the time for Flying has begun. Daniel R. Heath - Lexington, SC -------Original Message------- The correct way as Bud explains is to do the stick tap test. It was also explained by the RV test pilot at the first Mt Vernon gathering. You need to increase your speed 2 MPH at a time and give a quick slap to the stick to excite the ailerons. The stick should snap back then dampen out very quickly. You go up in speed slowly just until you see a change in the dampening response then stop. _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
