This is what I think this topic shortly:
1) we could fix permanently the tabs and stop
trimming but then we have to
accept we loose also anti-servo-function which is
necessary to generate some pilots stick forces.
Flying with zero pitch forces by stick would be
nauseous and
dangerous.
2) trimming function is there just to zero trim
tabsanti-servo
loads when tailplanes are in their desidered
position = when trimming pilot is in fact
in-lining the
tabs with the tailplanes to zero the stick forces.
Stick loads means the tabs must be deflected more
or less, no
stick loads means the tabs are in-lined with
tailplanes = the plane is trimmed.
3) if the trim tabs are slightly deflected when
the plane is trimmed and there are no stick
forces, it means some unperfection with
tailplanes shape (foam structure, no NG factory
made).
4) " aerodynamically balanced " tailplanes = the
forces which try to turn the tailplanes clockwise
are always equal with the forces which try to turn
them anticlockwise.
That is why they could float in any position any
time (without anti-servo function or pilots hand
which keeps the stick steady).
Frans, do you now have more photos with varying
speeds and CofGs ?
Raimo
--------------------------------------------------
From: "JonSmith" <jonsmitheuropa@tiscali.co.uk>
Sent: Tuesday, May 25, 2010 11:00 PM
Subject: Europa-List: Re: Effects of Flaps and
Ailerons on Pitch Trim
> <jonsmitheuropa@tiscali.co.uk>
>
> Hi Jos & Graham, My theory about the tailplane
> was based on the principle of a FULLY
> aerodynamically balanced "all moving" tailplane,
> this being the perfect situation for efficiency.
> (Jos - MY interpretation of "aerodynamically
> balanced" being specifically related to an "all
> moving" tailplane that is not deflected at all
> from it's current position by it's relative
> airflow, including any changes to that airflow,
> ie the center or point of the lifting force
> (downforce) generated by the tailplane acts
> through the pivot (torque tube))
>
> However, IF Graham's info about the C of L being
> deliberately designed to be NOT quite acting
> through the pivot (due to this short period
> oscillation - whatever that is!) is true, and I
> am very pleased and interested to bow to his
> most extensive experience of the Europa
> development and learn about this, then this
> means that the Europa tailplane is not quite
> perfectly aerodynamically balanced. Thus,
> unless the Angle of Attack of the tailplane is
> at any time zero (most unlikely) then a small
> tab deflection in the relevant direction would
> be required to counter the rotating force
> created on the tailplane by the airflow. (I
> would class this as another "unwanted"
> rotational force as in my previous text under
> variances!). This rotating force - and the
> corresponding amount of tab deflection required
> to offset it to maintain trimmed flight would
> vary slightly depending on the relative airflow
> to the tailplane and the corresponding amount of
> lift (downforce) being generated. This!
> aerodynamic imbalance of the tailplane must I
> feel only be slight - the whole downforce
> generated by the tail is fairly small and is
> needed just to balance the wing's own imbalance
> of forces.
> (Question - WHY then are some people's tabs
> completely flush in steady trimmed
> flight.....?!)
>
> This aside though, I still fully stand by my
> comments of how the tailplane, especially the
> tabs work in principle. The tabs, when trimmed
> by the pilot correctly, hold the tailplane in
> the desired position as set by the elevator
> control. The tabs would ideally be flush (fully
> aerodynamically balanced tailplane) but will
> have a permanent, slightly variable deflection
> if Graham's info on the tailplane not being
> fully aerodynamically balanced is true (as I'm
> sure it is..!)
>
> Jos - of course the trim control is necessary -
> vital in fact to keep the elevator control where
> the pilot wants it and to provide "feel" or
> "weight" (the anti-trim part as you call it) to
> the stick to stop the pilot "breaking things" as
> you most eloquently put it! But I think that
> without trim tabs fitted the elevator control
> would be VERY LIGHT to move (not heavy)
> throughout the entire range, dangerously so
> without extreme care. A perfectly
> aerodynamically balanced (all moving!) tailplane
> without trim tabs fitted would be completely
> without weight or feel at all throughout the
> entire elevator range (most undesirable). The
> trim tabs we have are very powerful being so far
> from the torque tube and if set even slightly
> out of the correct trimmed position would make
> the stick very heavy to hold in position. This
> of course is not force generated by the
> tailplane itself, rather the (rotating) force
> being applied to the tailplane by the
> incorrectly set trim (tabs).
> Best Regards, Jon
> (Sorry about the length again!)
>
> --------
> G-TERN
> Classic Mono
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=298854#298854
>
>
> browse
> Un/Subscription,
> Chat, FAQ,
> http://www.matronics.com/Navigator?Europa-List
> Web Forums!
> List Admin.
>
>
>
|