I found this the most informed answer to why not to use a Biased handle. Thanks for clearing that up, makes sense.
I found this the most informed answer to why not to use a Biased handle. Thanks for clearing that up, makes sense.
Let me add this extreme example of what Randy is explaining. I've told this story a number of times but it never seems to eliminate the repeated questions about biased versus non-biased neutrals.
A late very good friend and flying partner for several decades, Bill Fitzgerald, was having a problem with his "WAM Class A stunt ship" a Sig Banshee with a Veco .19BB in it. Now I know Bill was a fine flier because he and I had many a battle back in '60s as advanced and then expert WAM fliers. I also know because he spawned a brash kid named David Fitzgerald who utilized genius DNA, talent and dedication to become a pretty successful stunt pilot as well. Lost count of the number of times his name is on the Walker Trophy but I do know there's only one name on it more often than his.
Daddy Bill flew well despite flying with a significantly biased handle position at neutral and was sort of in the forefront of the adjustable handle era as he modified Hot Rocks with an aluminum bar in front that allowed adjustable line spacing. (This was a long time before Bob Baron made the adjustable handle ubiquitous in the stunt world). He also liked to fly with a lot of handle movement for a given airplane response (i.e. slow controls) which he accomplished by using narrow handle line spacing in concert with the then "standard" three inch bellcrank and Veco Control horns (the largest pushrod arm of which was only 1/2 inch...although the Banshee probably had the then latest thing, bolt on nylon, horns [probably Perfect, but don't quote me]). The problem was that, despite this attention to detail and then state of the art handle adjustability, the dang thing wouldn't turn outsides!
In either case the on-board system lent itself to pretty fast controls so Bill achieved his desired slower response rate by narrowing the line spacing at the handle as mentioned above. The airplane itself was built with Bill's typically exacting attention to control system detail. The controls when activated by the leadouts on the ground provided plenty of flap/elevator deflection...on the bench everything looked just fine!
When Bill grew frustrated with the lack of outside turn on the Banshee he asked if I would fly it and see what I thought. I did so using his handle as he had it set up. For me it was very difficult to fly because it had "instant" up control and almost no down control using my preferred inputs. In fact, when I simply held max down displacement a very large outside loop was the best result obtainable. An outside square corner was out of the question...as Bill had stated repeatedly.
After landing, I asked if I could put my own handle on the ship and fly it again with my preferred vertical neutral and handle line spacing. “Sure”, Bill said and we launched again. As if by magic, the airplane flew just like Banshees of my own and I was able to fly the airplane competitively...the outsides were just fine and nice tight squares were a cinch.
A light bulb lit up in my cranium. After landing I put Bill's handle back on the lines and did an experiment. First, we gave full up control and the flap/elevator deflection was exactly the same as when the leadouts themselves were pulled...full up!
When, however, down control was applied (full down with the grip parallel to the ground and the up and down lines totally overlapped) there was only a fraction of the down control deflection that was available when they were activated manually by the leadouts.
The combination of the very narrow line spacing at the handle combined with the relaxed (biased) neutral setting simply did not allow the pilot to access the control displacement provided by the on-board system. At least half of what was built in was unavailable!
Granted, this was an extreme example but it was not the only such airplane I've found afflicted by exactly the same physical control system flaw. One other was the competition airplane of a very competitive flyer at a major west coast meet. I only looked at the airplane closely because I had been alarmed when he flew his outside square corners because doing so required that his arm be extended straight down with--just like Bill's--the lines laying on top of one another at the handle supplying all the down control the handle was capable of providing. In the pits after the flight I surreptitiously performed the same experiment; inputting down from both the handle and by pulling the leadouts at the airplane and found that, as with Bill’s Banshee, it was not possible to obtain full available down control utilizing the handle.
This inability to obtain all the down available has been and most certainly will in the future be thought by the pilot to be an aerodynamic trim problem with the airplane itself which will be addressed by the pilot in ways that will compromise rather than enhance the performance of the entire package.Aside from the compromises this places on flying well and consistently--especially in demanding air conditions--the “down” biased handle will require some degree of movement of the pilot’s entire arm down and away from the airplane which will simultaneously pull the airplane toward the pilot increasing line tension and altering the trimmed yaw relationship so carefully established during flight trimming the leadout guide position.
This is so because--unlike up control which allows the pilot multiple sources of handle displacement with more modest “toward the pilot” forces: wrist, finger, elbow and upward arm movement at the shoulder or any combination thereo--enhanced down control requires what little down wrist deflection remains after the neutral bias plus moving the entire shoulder to finger complex downward and back ward. (Note also that the axis of rotation of all but the tiny bit of left over down angle of the wrist is at the shoulder which multiplies the “muscle” necessary to input that additional control deflection. IOW, the problem multiplies itself. The "human" end of the control system is not symmetrical and, for best performance, the effect of that asymmetry should be limited to the greatest degree possible.
None of the above are an asset to flying excellent, repeatable CLPA tricks!
Ted
Topic: Hard Point vs EZ adjust (Read 7807 times)
