Quote:
Originally Posted by robtek
@ taildraggernut
ok, you've wrote at first NACA document, but you meant a Nasa-document about the Naca-document.
And you didn't flatter me, i meant sugarcoating, english is not my first language.
All those chaps with 10 h were those who did fly so carefully that they were outturned by 109's, maybe.
@ Al Schlageter
Of course light elevators ARE desirable, it's the combination with short stick travel which may cause problems for the less experienced.
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Does it matter much? does the fact it is a NASA document about a NACA document invalidate it? is it impossible to ascertain what I was refering to? I don't quite follow the need for that correction.
Sorry but english is my first and only language, I simply assumed you used such an uncommon word because you knew what it meant, I had no warning that you may not have understood the words you are using.
so none of the chaps survived an engagement with a 109? despite the fact....sorry anecdotal fact.....that new guys were told to turn as hard as they could in order to evade the 109?
with regards to short stick travel this is apparently another desireable quality, from another part of the same article, interstingly you will se that research was put into trying to make control forces 'light', now apparently this is what makes the Spitfire 'tricky', but what it actually did was compensate for the slight instability and made it more controlable.
Quote:
The Quest for Reduced Control Forces
One of the most serious problems encountered by designers of military airplanes during WW II was keeping control forces desirably light while airplanes were being made with greatly increased weight, size, and speed. Flying qualities research had shown that maximum control forces should be kept below what a pilot could conveniently exert with one hand on the control stick or wheel. For ailerons, this force was about 30 pounds on a control stick or 80 pounds on a control wheel. Increasing the mechanical advantage of the pilot's controls was impossible because of the limited size of the cockpit and the lag in deflecting a control wheel more than plus or minus 90 degrees. Studies of aerodynamic balancing devices to reduce the aerodynamic moments on control surfaces became one of the main research objectives of wind tunnels involved in stability research.
Aerodynamic balance on most airplanes designed prior to WW II was usually accomplished by locating some control surface area ahead of the hinge line. Various arrangements of these balances are shown in figure 6.1. These balances had advantages and disadvantages from both mechanical and aerodynamic standpoints. In general, balances that were permanently located in the air stream were subject to icing that might jam the controls. Balances that broke the contour of the airfoil added drag. In addition to such practical considerations, balances had to be selected on the basis of the hinge moment parameters such as the variations of control surface hinge moment with angle of attack and with control deflection. These parameters had fundamental effects on the flying qualities. The effect on snaking oscillations of the variation of hinge moment with angle of attack has already been mentioned. To obtain light control forces, both of these parameters had to be reduced.
Theoretically, the control forces could be reduced to zero by reducing these hinge moment parameters to zero, but in practice this goal could not be attained. One problem was the nonlinearity of the hinge-moment variations. For example, a control surface that was properly balanced at low deflections might be overbalanced at large deflections. A second problem that limited the degree of aerodynamic balance on large and high-speed airplanes was the effect of small changes in contour due to manufacturing differences. These differences might be almost too small to detect, yet could cause quite large changes in the control forces. The Germans, in an effort to obtain very light aileron forces on the Me109 airplane, would test fly the airplane and try different sets of ailerons until one was found that would give forces in the desired range. The British, on testing the Spitfire, mentioned encountering "rogue" airplanes that had different characteristics from the standard airplanes, the reasons for which could not be detected.
As a result of these problems, a practical limit had to be set on the degree of aerodynamic balance, which was usually 25 to 30 percent of the forces produced by an unbalanced control surface. This degree of balance, however, was nowhere near what was required to provide desirable handling qualities on the largest or fastest airplanes. In some cases, forces would have to be reduced to about 2 to 4 percent of those of an unbalanced surface.
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