REFLECTOR: Porpoising (was TruTrak AP)

[Pat Shea]

Chuck,

Does your plane porpoise much without the a/p engaged?
My XL tends to porpoise at high cruise (180KIAS) with
only one person in the front seats. It settles into
1-2 minute cycles with an amplitude of +/- 5 knots.
Hands off, it's not a very comfortable ride. Brendan
suggesested increasing the negative incidence on my
sparrow strainer to further load the pitch trim spring
at high cruise. This would also cause the plane *feel*
less pitch sensitive at high cruise which is fine. He
mentioned this before I told him that my sparrow
strainer has only about half as much negative
incidence as most I've seen - that's just the way it
came out using the templates. I knew it was off but
decided to just try it first to see - I may now be
*seeing* the results. An a/p would probably take care
of this, but I'd like the plane to be dialed in on
it's own if possible.   

Pat XLRG

- Chuck Jensen <cjensen at dts9000.com> wrote:

> Al,
>  
> I'm fitted with a TruTrak Digiflight IIVSG (or
> something 'ruther).  The TruTrak has an 'activity'
> setting for the pitch and roll axis that be used to
> can compensate for the flying characteristics of
> most planes.  In general, the TT is rock solid with
> no porpoising or rolling--smooth or turbulent--once
> the activity level is set.  The only 'slop' in my
> control system is in the left seat.  If the plane is
> rigged properly, the TT A/P should handle it no
> problem.
>  
> Chuck

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