|
Joe,
Actually it is GOOD that the discussion and short films regarding flutter are a little (or a lot) unnerving. I have also spent 20 years doing crash investigations and have buried a few friends in that time.
There is a lot to be said for flying a proven design with lots of examples out there. Some designs fly for years on the ragged edge of a flutter problem and no one ever knows till someone makes the tiniest change, like adding a stall strip to the leading edge of a wing or changing the wing strut streamlined tube for one with a different cross section. With many examples flying there is a better chance that someone else has already tried what you are thinking of, and hopefully it didn't cause a problem. One typical problem (the one most dynamic stability classes use as an example) is changing the counterweight on a control surface. This isn't usually something someone does on purpose (if they are smart). What kills pilots without warning is when it happens and they don't even know it has changed. Ever look at the control surfaces on many planes where the skin is made of a flat piece of aluminum with stiffeners pressed into it? If the plane has enough counter balance to be stable and convergent as designed, what do you think would happen if mud daubers built nests in the trailing edge? The CG of the surface would move back, potentially past the static margin limit, making the surface unstable and prone to flutter. I almost lost a friend in a Cessna because of ice in the elevator. He was lucky and slowed down and got the plane back on the runway, but there was control system damage from all the control shaking. One of the really scary things I have seen is someone adding a Grimes rudder light a the back edge of the rudder. This is REALLY asking for trouble! On many high speed planes with fabric tail surfaces you are required to balance the surface to VERY tight tolerances when you recover or paint the fabric. We had to tear all of the fabric off of a C-118 rudder that looked perfect because the CG was 1/4" to far aft. Just a "little" to much dope! The bad thing was the plane was on its way to Davis Monthan for scrap.
Another is messing with the control gaps. Putting tape over the control gap can increase sensitivity and smoothness of the control, but if the tape comes part way off, it can also cause turbulent flow across the surface increasing the chances of flutter.
As to not doing a "once around the patch" and going for a full power climb to altitude, I wouldn't do that. The full power climb results in higher speed and there is a pretty good potential for inducing flutter at higher power settings. Move out in the flight envelope slowly! Raise the speeds a little at a time and explore the corners of the VN diagram in small well planned steps. It IS a good idea to climb to altitude (in case an emergency exit is needed) but there is NO HURRY to get there!
This is why I think a good flight test plan is important. You are absolutely right. There is MUCH to consider. The place to start may be a clear understanding of the VN diagram. I was a little shocked to find out how many pilots didn't even know what it is! If you don't know either, you are actually in very good company.
Hank
|