This is an interesting subject indeed.
I was taught that on an inherently stable aircraft (operating within its CG
envelope) with a tail, the tailplane is always exerting a downward force in
cruise to counteract the tendency of the wing to twist forward in the
airflow due to the lift vector. As opposed to a canard where the forward
wing provides lift, making it a more efficient design.
I'm perplexed - all the photos I've ever looked at of Europas in cruise, the
trim tab is *up* (as others have noted), thus the flying elevator is by
definition providing *lift* to the tail.... a contradiction to my
teachings.
Confused,
Pete
A239
On Mon, Apr 12, 2010 at 12:14 PM, Fred Klein <fklein@orcasonline.com> wrote:
>
> On Apr 12, 2010, at 6:24 AM, david miller wrote:
>
> I think that for most efficient flight the incidence of the wing and tail
>> should be such that at cruise there is no up or down trim on the elevator or
>> all flying tail.
>>
>
> Fascinating discussion...as a non-aerodynamicist, I can't resist the
> temptation to add a comment...
>
> I've always understood that the elevator or an all-flying tail (horizontal
> tail plane) has a "job"...namely, to exert a force, either up or down, in
> order to balance the lift of the wing and stabilize the flight path of a
> normally configured aircraft (i.e., not a canard type). To do this "job"
> requires "work"; the tail plane is never neutral. And w/ our Europae...with
> it's trim tabs acting in opposition to the all-flying tail plane thru a
> direct mechanical connection...whenever the tail plane is doing its job (at
> whatever angle of incidence), the trim tabs will be doing their job as well
> (that of counterbalancing forces on the tailplane), and will necessarily be
> raised or lowered w/ reference to the tailplane.
>
> Of course if this explanation is correct, one might ponder the aerodynamics
> of my tail-less biplane...pix below.
>
> Fred
>
>
--
"A man is not old until his regrets take the place of his dreams. "
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