REFLECTOR: Aerodynamic trim

[John Dibble]

Pat Shea wrote:

>
> Probably the easiest way to analyze the function of
> the "sparrow strainer" is to take it and the trim
> spring out of the picture. In that scenario, at high
> cruise speed the pilot would need to press forward
> (hard) on the stick to maintain level flight.

Actually, Duane swing claims that without either, very little stick pressure is
required and that is what causes instability.



> Now add
> on the sparrow strainer which will be pulling down on
> the trailing edge of the elevator with its inverted
> airfoil and negative incidence relative to the
> elevator, and the pilot has to push forward even
> harder. Yes, it's actually working against you at high
> cruise speeds.

I would say it works against you at all speeds.

> The pitch trim spring simply replaces
> this force required by the pilot. Therefore, the pitch
> trim spring has to work harder at high cruise speeds
> with the sparrow strainer installed.
>
> Here comes the purpose...
>
> Since the pitch trim spring is working harder, it is
> further "pre-loaded." This gives the stick a heavier
> (or stiffer, or whatever...) feel in pitch at high
> cruise speeds. This higher pre-loading of the pitch
> trim spring also makes the elevator (and therefore the
> plane) less susceptible to pitch deviations from
> turbulence, etc.
>
> What's all this mean? If you are prefer heavier stick
> forces at cruise and a little more stability, use the
> sparrow strainer. If you prefer lighter stick forces
> at cruise and are willing to forgo a little stability,
> take it off or even turn it into an aerodynamic
> trim...

I see no change in stability with it inverted.

John

>
>
> Pat
>
> --- John Dibble <aminetech at bluefrog.com> wrote:
>
> > Dave,
> >
> > I had the same problem with my SERG.  I reversed the
> > strainer and now I can descend at
> > 200 kn/1000 fpm and still have more trim available.
> > Reversing the strainer is a lot
> > easier than changing the trim spring.
>
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around
> http://mail.yahoo.com
> _______________________________________________
> To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html