REFLECTOR: Porpoising (was TruTrak AP)

[Chuck Jensen]

Pat,

It's agreed that the optimum solution is to 'dial it in', then add an A/P.  The A/P might be able to camouflage the not-quite-right rigging but I suspect you didn't spend 1000+ hours and 50% more money than expected, just to have a plane that can get airborne and kind of flies okay.  

If the problem is intractable, and after trying everything else, you can always try the A/P to solve the problem.  But since the consensus is for installation of an A/P anyhow, given the Velocity mission profile, it would seem to make sense to install an A/P, even if you haven't gotten every issue sorted out, because you'll eventually want one.  And, the TruTrak is a pretty solid choice (and I believe there is a competitive price available thru Velocity).

I'm not sure about the sparrow strainer issue.  That's been discussed in archive ad infinitum.  I took mine off (well, actually it fell off) but I haven't reinstalled it as I'm unable to figure out exactly what it will, or is supposed to, do for me.  Others swear by them.  I don't notice the before/after difference.

Final thought.  Rather than adjusting the sparrow strainer to fix your problem, may be it IS the problem.  Try removing it and see if the porpoising goes away.  Stranger things have happened.

Chuck 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
Behalf Of Pat Shea
Sent: Monday, May 16, 2005 10:05 PM
To: Velocity Aircraft Owners and Builders list
Subject: RE: REFLECTOR: Porpoising (was TruTrak AP)


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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