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Ian Crowe. Asks:
Can any of our more technical brethren in the aerodynamic field give us
some pointers as to what we are trying to achieve by balancing and to what
degree of balance we should aspire to?


The elevator control surface balancing is done to keep control pressures on
the stick constant when the aircraft is experiencing G forces. The main
thing to avoid is having the front of the elevators heavy. If the front of
the elevators are heavy the plane will over react to control inputs. When
you pull back on the stick, the G forces will pull the rudder up even more
and tend to push the stick back. This is control reversal you then have to
maintain forward pressure on the stick to keep the plane from rising
uncontrollably. The same reversal applies to pushing forward on the stick.
You can probably imagine, this situation is non intuitive, and makes it
very difficult to control the airplane. The best thing to do is get it
exact, or make the rudders a little heavy on the trailing edges.
Another way to think about it is the heavier the trailing edges are the
more sluggish your plane is going to be you will need muscle to pull
aerobatics maneuvers. The closer you get to the balance point the easier
your plane is going to respond to your control inputs. When you get beyond
the balance point, your plane starts to dangerously add to your control
inputs, so never go here.

Regards,
Ed
Watsonville CA.


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