Duncan
Your symmetrical loading theory is probably erroneous. The stabilator is
normally loaded downward (negative lift) when it is in a neutral position.
Therefore, it will take less downward deflection to reach the critical
(breaking) point. Upward deflection (12 degrees) gets to overcome the downward
loading before it even starts to give positive lift loads as it deflects
upward.
Regards
Tom Friedland A079
McFadyean wrote:
> All true. Only the structure of the tailplane and its support is
> symmetrical in a vertical plane. So if it will take 12 degrees or so in the
> "up" direction then it should take similarly in the "down" direction.
>
> Duncan McFadyean
>
> On Friday, February 01, 2002 6:14 PM, Dave Simpson
> [SMTP:dave_simpson@londonweb.net] wrote:
> > There's a bit of an airworthiness issue involved here.
> >
> > The tailplane, like the rest of the structure is proven to take certain
> > loads calculated from speeds and control surface deflection. In the case
> of
> > the tailplane/elevator, it's either 1/3 full deflection at max dive speed
> > (actually around 1.1 x Vne) or full deflection at Va, whichever is the
> > greater. So if the surface and its supporting bits are stressed for
> these
> > loads, then it should not be permitted to experience more than these in
> > service, otherwise we're nibbling away at the safety margins.
> >
> > Roughly the load on the tailplane is proportional to its deflection. So
> an
> > increase from +4 deg. to +6 deg. results in a 50% increase in load.
> >
> > So you might break it off.
> >
> > Dave
> >
> >
> > ----- Original Message -----
> > From: <DJA727@aol.com>
> > Subject: RE: Tailplane mass balance stops
> >
> >
> > > A question,
> > >
> > > If you have a 6 degree travel at full deflection and 4 degrees is
> > required, why would that be a problem? I would think that less that 4
> > degrees would be a problem, not more. One problem I have dealt with is
> the
> > definition of the neutral point of the elevator. I have the required
> travel
> > up and down, but it really hinges (no pun intended!) on where you make
> that
> > point of zero degrees. One would hope to never actually hit that limit of
> > travel unless in an emergency.
> > >
> > > Just wondering out loud.
> > >
> > > Dave Anderson A227
> > >
> >
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