Re: Mechanics of Elevator Trim. In Detail.

On Jun 12, 9:53 pm, Ron <r...@[EMAIL PROTECTED]
> wrote:
> On Thu, 12 Jun 2008 09:43:07 -0700 (PDT), "Ken S. Tucker"
>
> <dynam...@[EMAIL PROTECTED]
> wrote:
> >On Jun 12, 5:08 am, Tina <tbaker27...@[EMAIL PROTECTED]
> wrote:
> >> > Yes, the time my son spent with canard aircraft brought out all
sorts
> >> > of interesting information about canards and the history of trying
to
> >> > scale up Rutan's original concept Beech Star****p.  The smaller true
> >> > canards like the Long-eze are pretty good aircraft.  However there
is
> >> > a reason why we don't see large (six plus passenger) true canards.
> >> > It's the relation****p between CG, fuel load, payload and range.
> >> > Apparently in the scale up process there is a point where it is no
> >> > longer practical.
> >> > Ron Kelley
>
> >Hmm, how the XB-70 or this,
> >http://en.wikipedia.org/wiki/Boeing_Sonic_Cruiser
>
> True, the XB-70 was a qualified success of a large canard type
> aircraft.  Most of it's problems were due to system failures and
> trying to fly at Mach 3.0.  The only control issues I know of were
> related to overly sensitive pitch response to control inputs. 
Ref:http://www.labiker.org/xb70.html

Thanks for that link.

> As far as I know the Boeing Sonic Cruiser hasn't gone beyond the
> artists concept stage.  I guess it's no accident that all the current
> crop of passenger jets look alike.  That could be partially due to the
> reluctance of any large airframe manufacturer to take a gamble on
> trying to certify any new "radical" design.  Who knows.
>
> Personally, I am intrigued by the three surface aircraft like the
> Piaggio.  They seem to have done pretty good with their design. One
> wonders if given enough time, money and talent, there is some room for
> improvement there.

Yes! That Piaggio is one real impressive piece of
aerodynamics, and it sounds very pilot user-friendly.
Very remarkable how they utilized the canard.

> >I think the aircraft business is extremely conservative.
> >KISS applies, also canards are difficult for the average
> >pilot to understand, (Hey man, you got that thar tail on
> >the wrong end :-).
>
> >> Would it not also be true that passive stability is not as im****tant
> >> in larger modern airplanes? I would guess (again, I admit being
> >> ignorant of the realities) that adding a 10% aerodynamically induced
> >> increased load on bigger aircraft would be avoided for efficiency
> >> reasons? It might be better to have enough fly by wire and computer
> >> induced stability instead.  I don't know enough about this stuff to
> >> even find the back of an envelope, let alone do a calculation there.
>
> >Canards are NOT simple, I've designed quite a few,
> >and studied others, especially Rutan's.
> >I find they can be optimised for a given air speed
> >and are much better than the conventional lay-out.
> >The main problem is designing the stall.
> >Ken
>
> Anyone who can design a successful canard aircraft has my respect.  I
> didn't learn a whole lot about the design aspects from my son (he was
> in flight test, not design), but what we did learn was everything
> interacted with everything else.  The job was interesting, but didn't
> last long.

Your son sounds like a cool dude.
The major PITA is designing aircraft to be efficient
at cruise, but safe all the way to stalling, and
recoverable. The difficulty is the movement of the
Center of Lift forward on the main wing as stall
begins.

> Ron Kelley

Regards
Ken