Reflector: elevator stick forces

[Pat Shea]

"Alexander Balic" <alex157@direcway.com> wrote:
<<Steve,
Yes, the designed function of the sparrow strainer is
to aerodynamically trim the elevator- without it, you
are loading up the trim spring at higher speeds, and
thereby making the pitch authority stiff. With the
sparrow strainer, the little inverted wing unloads the
pitch spring...>> 

Alex and Steve,

 Actually, at higher speeds FORWARD stick/trim force
is needed to bring the trailing edge of the elevator
up enough to maintain level flight. Since both the
sparrow strainer's inverted airfoil and its negative
incidence are working to pull the trailing edge of the
elevator down, the strainer actually INCREASES the
stick/spring force needed at higher speeds. In other
words, adding the strainer will make the plane LESS
pitch sensitive (i.e., more pull needed in a turn) at
these speeds. This also explains what Ronnie Brown
experienced after putting on his strainer: "it caused
the nose to require less up trim, so much so that I
don't quite have enough down trim when I am flying by
myself and in a power on descent which is higher speed
than cruise. But it works great when I have a
passenger."
 Conversely, having the strainer on will work to
reduce the stick/spring force needed at lower speeds
since in ths situation the trailing edge of the
elevator needs to be down to maintain level flight. 
 According to Scott Baker, the primary function of the
strainer is to dampen out pitch deviations from say
light turbulence. We already have an trim system, it's
electric...

Pat

               

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