REFLECTOR: Pitch Trim Mystery

Scott Baker sbakr at comcast.net
Thu Feb 16 18:43:41 CST 2006 

I agree.  2" of up elevator during fast cruise to a bit much, even with an
aft CG.
It might be time to:
a)    reduce the canard incidense angle a bit
b)    relocate some equipment to the nose area of the aircraft to move the
CG forward a few inches
c)    reduce the incidense angle of the main wings a washer width
c)    invite more friends to fly along
:-)
Look for maybe 0.5" up elevator during fast cruise.
SB



----- Original Message -----
From: "Rene Dugas" <dugasd at bellsouth.net>
To: "'Velocity Aircraft Owners and Builders list'" <reflector at tvbf.org>
Sent: Thursday, February 16, 2006 6:56 PM
Subject: RE: REFLECTOR: Pitch Trim Mystery


> John,
> Two inches up seems awfully high from what I have heard over the past 6
> years of reflector monitoring.  My XL RG at 174 economy cruise trailing
> edge is up 1/8th inch.  Stall is about 65 knots  No VG's.   At 190 knots
> TE is up maybe 1/4th inch.  At 210 knots in a slight dive it is not up
> even 1/2 inch.  I take off pilot only with TE down 1" with 100 #'s over
> gross 2800 pounds it is down 2 to 2.5 inches(just reference numbers.
> Rene'
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of John Dibble
> Sent: Thursday, February 16, 2006 3:56 PM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Pitch Trim Mystery
>
> I think the need for down trim is just a function of cg and speed.
> Since I'm at my
> aft cg limit (actually beyond the limit according to the standard
> Velocity
> calculations), I will need more trim than if I was not so aft cg.  My
> guess is I have
> about 2" elevator up at cruise.
>
> John
>
> Alex Balic wrote:
>
> > Hmmm, Well, probably a good idea to keep the incidence as is then, but
> I
> > think that it is a bit unusual for you to need so much down trim in
> cruise-
> > maybe a smaller/no strainer would work best for you- how much actual
> up
> > elevator do you have at top cruise?
> >
> > -----Original Message-----
> > From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]
> On
> > Behalf Of John Dibble
> > Sent: Thursday, February 16, 2006 1:19 PM
> > To: Velocity Aircraft Owners and Builders list
> > Subject: Re: REFLECTOR: Pitch Trim Mystery
> >
> > Alex,
> > Thanks, but when solo, my canard barely stalls, more like a mush.  I'm
> > concerned that
> > less incidence might put me in the deep stall mode.  Besides, the
> weight is
> > just a
> > temporary thing anyway. I'm currently getting 180-182kn with my
> Franklin/IVO
> > and I
> > hope to get a few kn more once the trim issue is resolved and I can
> use full
> > power.
> >
> > Alex Balic wrote:
> >
> > > John-
> > > In lieu of adding the weight- you might think about dropping the
> canard
> > > incidence about a degree- will give you more speed too...
> > >
> > > Alex
> > >
> > > -----Original Message-----
> > > From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]
> On
> > > Behalf Of John Dibble
> > > Sent: Thursday, February 16, 2006 12:09 PM
> > > To: Velocity Aircraft Owners and Builders list
> > > Subject: Re: REFLECTOR: Pitch Trim Mystery
> > >
> > > Steve,
> > > I have one installed.  I need to check, but I believe it wroks
> against the
> > > spring, so
> > > I guess I need to reverse it.  How much work is involved to do that?
> > >
> > > Scott B - I believe you mentioned that reversing the strainer could
> cause
> > > instability.  How can I flight test for this?
> > >
> > > In the meantime, I plan to add 20lb to the nose, so I won't have to
> use
> > the
> > > full trim
> > > adjustment at cruise.
> > >
> > > John
> > >
> > > steve korney wrote:
> > >
> > > > A lite spring and a external trim tab would solve that
> problem.....
> > Like
> > > a
> > > > sparrow strainer
> > > >
> > > > Best... Steve
> > > >
> > > > ----Original Message Follows----
> > > > From: John Dibble <aminetech at bluefrog.com>
> > > > Reply-To: Velocity Aircraft Owners and Builders list
> > <reflector at tvbf.org>
> > > > To: Velocity Aircraft Owners and Builders list
> <reflector at tvbf.org>
> > > > Subject: Re: REFLECTOR: Pitch Trim Mystery
> > > > Date: Wed, 15 Feb 2006 11:28:10 -0600
> > > >
> > > > Well, that sounds like a good guess.  For the entire flight either
> the
> > > > autopilot or
> > > > myself was adding a little extra pressure to maintain level
> flight.
> > After
> > > I
> > > > got out
> > > > of the plane I pushed down on the elevator a little.  Maybe that
> is what
> > > > made it work
> > > > again.  I'll check it out.  But wouldn't pulling back on the stick
> also
> > do
> > > > the same
> > > > thing?  Or am I not understanding this right?
> > > >
> > > > Scott - It took a lot of force and of course the farther I pulled
> back,
> > > the
> > > > stronger
> > > > the force.  It felt like I might break something.  I suppose you
> could
> > > trim
> > > > your
> > > > elevator all the way up and feel the force to pull the stick back
> to
> > > > neutral.
> > > >
> > > > John
> > > >
> > > > Alex Balic wrote:
> > > >
> > > >  > The pitch trim jack screw has an internal "switch" that turns
> it off
> > in
> > > > the
> > > >  > particular direction of travel that would bottom it out-
> possibly
> > this
> > > is
> > > >  > just slightly out or the contact is burned, hard to tell- not
> sure if
> > > you
> > > >  > could even open it up to check that - you might want to do some
> > > >  > experimenting- see if you run it all of the way to the bottom
> and you
> > > > force
> > > >  > it if it might move just a bit more and loose contact
> internally,
> > after
> > > >  > relieving pressure, apply pressure in the opposite direction-
> might
> > > move
> > > >  > back just a tiny bit to regain contact again- just a
> guess......
> > > >  >
> > > >  > -----Original Message-----
> > > >  > From: reflector-bounces at tvbf.org
> [mailto:reflector-bounces at tvbf.org]
> > On
> > > >  > Behalf Of John Dibble
> > > >  > Sent: Wednesday, February 15, 2006 10:46 AM
> > > >  > To: Velocity Aircraft Owners and Builders list
> > > >  > Subject: REFLECTOR: Pitch Trim Mystery
> > > >  >
> > > >  > Seems like when the Reflector has a what-if discussion, soon
> after
> > > > someone
> > > >  > has to go
> > > >  > out and experience it.  I guess the pitch trim failure had my
> name on
> > > it.
> > > >  > Last night
> > > >  > I flew 1.7 hrs at 180 kn with the pitch trim pegged at down
> trim.  I
> > > cut
> > > >  > power just
> > > >  > enough to descend at 500 fpm and kept the trim pegged.  At 5
> miles
> > out
> > > I
> > > >  > slowed to get
> > > >  > set up for landing and noticed the pitch up trim wasn't
> working.
> > > >  > Fortunately I've
> > > >  > flown at night enough, so that that didn't add much to the
> problem.
> > I
> > > > had a
> > > >  > 5000 ft
> > > >  > runway and a direct 10kn headwind which was a good thing.
> Didn't
> > know
> > > > how
> > > >  > long my arm
> > > >  > would hold out so I took the fastest way in and kept my speed
> up to
> > > 90kn.
> > > >  > Wasn't sure
> > > >  > if I could hold it off at 70.  The landing was a little rough,
> but
> > I've
> > > > done
> > > >  > worse.
> > > >  > Today I checked it out and the trim is working fine.  Can
> anyone tell
> > > me
> > > >  > what
> > > >  > happened?  I have fuses and no CBs so it wasn't that.
> > > >  >
> > > >  > John
> > > >  >
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>
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