Bud Davisson, who is about one of the most respected people in aviation, had some recommendations on the Midget Mustang group several years ago. He said you want to simultaneously pull power, pull the nose up, and load the ailerons. By loading the ailerons you bank, I guess the theory is to have the linkage pushing one way while airflow is pushing the other way instead of leaving them free to flutter. So basically yank and bank. Put a few G load on the wings to rapidly decrease speed. I didn't say yank them off though.
He also gave instructions for finding your flutter speed which involves slowly increasing your speed and tapping on side of the the stick. It should move when you tap and then bounce back to neutral without overshoot. As soon as it starts to vary from that motion you are approaching your flutter speed and you need to stop there. What many don't realize about flutter is that you might accelerate right past your flutter speed without even realizing you are there. A little bump on the aileron or slight bit of turbulance can start the chain reaction that can start flutter and rip your wings right off with no warning before you even have a chance to recover. Just because you did a 230 MPH flyby in the past is no guarantee that you won't be at 220 next time and hit the little bump that makes you a statistic. If you have not done the stick tap test in 5 MPH increments, preferably at altitude and with a chute then you have no business flying in those speeds. I am not saying that you need to keep testing until you find the flutter speed if you start getting nervous, but if you stop your testing at 200, don't be doing low passes at 220, do them at 195. I will try to find his email and repost it here. I think I might have done it many years ago if someone could be so kind as to try and find it in the archives. Several things will increase the speed at which you will get aileron flutter. One is the design of the wing and aileron system which we have little control of. One is making sure the aileron is balanced, and that means balanced after it is painted. Another is making the mass of the aileron and balance weight as light as you can. I have said here many times that when you do the balance weight you want to use as little weight as you can which means in order to balance a given weight of aileron you need the mass of the weight as far from the hinge point as you can get it. Jim Faughn had balance weights that were shaped like small bricks and were so heavy one broke off at a gathering. There was a lot of weight close to the hinge line as opposed to making it tear drop shaped with more weight further from the hinge point. Also, make the aileron light weight so you don't need as much weight to balance it and so the whole aileron and balance mass is lower. Aileron in one layer of carbon fiber and foam sanded with extra care so no dips needing a lot of filler goes a long way to a strong and light aileron. don't use extra epoxy here. Stiffness also helps. Again, I would use carbon fiber for aileron even if I was making wing out of glass. Obviously glass has worked well for years, but if you are going to insist on flying past design speed you may be pushing your luck. No slack or flex in the aileron system. On my Midget mustang the rod ends had no slack, but you could clamp one aileron to the wing and flex the other several inches up and down. The skin on the sides of the fusalage where the belcranks were mounted would flex a bit which led to lots of flex possible over the entire system. I always clamp two boards on one wing and aileron on all planes not and look for play and flex in the system. Most people have never done that and you might be shocked at what you find. The Midget Mustang had a pre-flutter condition known as shudder. It was a lower frequency form of not full developed flutter. Flutter is more of a buzz that does not last long before parts start departing the airplane. Most planes don't exhibit shudder to give you a warning, they just flutter and then come apart. I have experienced shudder in my Midget Mustang and, yep, the first time was during a high speed pass trying to impress people. I can tell you that there is no amount of scaring the crap our of yourself that compares with this. That was before I learned more about shudder and flutter. After that I moved my balance weights further from the hinge line and removed the flex and did the stick tap test which moved my flutter speed way up and I made sure to not approach that speed again. Brian Kraut 904-536-1780 [email protected] -------- Original Message -------- Subject: Re: KR> Flutter From: Kayak via KRnet <[email protected]> Date: Sat, January 13, 2018 10:15 am To: KRnet <[email protected]> Cc: Kayak <[email protected]> I brought up flutter recovery several months ago from someone who had encountered it, and again under this thread. I wish we could discuss recovery. My late friend said to me (some 30 years ago), not to apply ANY control input (unless absolutely necessary to avoid the ground) and just take off the power instantly, for best chances to survive. This made sense to me because that much activity of movement requires energy. Don't feed it with engine power. The energy supply will then be the inertia of forward movement of your airframe, and will bleed off, hopefully before your airplane pieces "bleed off". He said everything went totally blurry and it happened almost instantly, couple seconds. This was, as I said, at about 221mph out of shallow dive. The cause was repainting his plane and then not re-balancing the control surfaces. And, IIRC, he had exceeded that speed prior to the repaint with no flutter. I agree that 200 VNE should be sufficient for this airplane. Keep things balanced, as Mike said, tight controls end to end, and if u get flutter as far as I know, no control pressure, chop the power. If you reach for the throttle and it's not there, flutter won! ;) On Sat, Jan 13, 2018 at 11:48 AM, Mike Sylvester via KRnet <[email protected]> wrote: > I'm glad you guys are discussing this. _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/[email protected]/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to [email protected] _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/[email protected]/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to [email protected]
