Why the T-Tail?

There are actually 3 variants 4 if you count the fixed U/C one
they are
B4 PC11
B4 PC11A
B4 PC11AF

Peter.


Hey Peter...I missed that! I never knew there was a fixed gear version.

I had a B4 for a few years and I think it was the best metal work I've ever
seen.

Come to think of it, I once saw a yellow one and a white one, so that makes it
five ;-)

Jim Vincent
N483SZ
illspam

Whats your point the B4 is a T Tail, I fly one

Someone implied that aerobatic gliders don't have T tails.


Rgds,

Derrick Steed

Derrick Steed wrote:

Someone implied that aerobatic gliders don't have T tails.

It was me. I wrote: Any *serious* aerobatic plane ... etc. The point is,
the B4 was *not* designed as an acro glider. Only later they found that
due to it's superior handling it would make an ideal acro glider. The
structure had to be reinforced, though, to allow flick maneuvres ...
exactly because of the huge torque forces caused by the T-tail.

BTW: There are many gliders which are certificated for some acro
figures: ASK-21, DG-500, DG-1000 just to name a few. All of them have
T-tail, none of them is primarily an acro glider, all are cross country
gliders which just happen to be allowed for some simple acro figures,
and, you guessed it, none of them is certificated for flick maneuvres.

Stefan

Stefan wrote:
BTW: There are many gliders which are certificated for some acro
figures: ASK-21, DG-500, DG-1000 just to name a few. All of them have
T-tail, none of them is primarily an acro glider, all are cross country
gliders which just happen to be allowed for some simple acro figures,
and, you guessed it, none of them is certificated for flick maneuvres.

The flight manual for my T-tailed DG-303 Acro allowed flick maneuvers
and tail slides...

Marc

Marc Ramsey wrote:

The flight manual for my T-tailed DG-303 Acro allowed flick maneuvers
and tail slides...

Lucky you. Lucky me that I didn't explicitely mention the DG-300.

Seriously, I only wanted to say that all airplanes which are primarily
designed for serious, competitive aerobatics have a "conventional" tail.
All which I know, that is. (And yes, the salto has a V-tail, which isn't
worse, torqueforcewise.)

Of course there are many airplanes with T-tail which are allowed for
aerobatics to some degree, and some might even be allowed for flick
maneuvres.

What was the question again? Ah, pros and cons of T-tail vs. conventional.

Stefan

Marian Aldenhövel wrote:
Hi,

I have noticed that most if not all modern gliders are built with a
T-Tail (not sure about the term, I am talking about the elevator being
located at the top of the tailfin). While most power-aircraft I know
right up to the airliners have it at the bottom.

What are the aerodynamic or constructive reasons for that?

Aerodynamics, Ha! It looks cool. That's what sells gliders.
;-)

Shawn

FYI: Flick half rolls are allowed in the DG-1000 (18M).

BTW: There are many gliders which are certificated
for some acro
figures: ASK-21, DG-500, DG-1000 just to name a few.
All of them have
T-tail, none of them is primarily an acro glider, all
are cross country
gliders which just happen to be allowed for some simple
acro figures,
and, you guessed it, none of them is certificated for
flick maneuvres.

Stefan

Quote: " I see no significant difference in the pitch torque generated
by a T
tail and a conventional tail (apart from a minimally longer arm for a T
tail on a given typical glider design).

"Am I missing something?"

Yes. It's not pitch torque that is the issue. It is the torque on the
fin/fuselage junction about the glider's longitudinal axis, caused by
asymmetric and/or inertia forces of a tailplane mounted at the top of
the fin - maximum moment arm. That is much greater than from a
tailplane on or close to the fuselage level where its moment arm is much
less. I had a share in a T-tail glider where the fin/fuselage area
delaminated during a final glide with violent oscillations of the whole
empennage before the pilot reduced speed and landed safely.

Chris N.

Marian Aldenhövel wrote in message ...
Hi,

I have noticed that most if not all modern gliders are built with a
T-Tail (not sure about the term, I am talking about the elevator being
located at the top of the tailfin). While most power-aircraft I know
right up to the airliners have it at the bottom.

What are the aerodynamic or constructive reasons for that?

Ciao, MM

It's nothing to do with aesthetics. It's just a happy coincidence
that aerodynamically efficient structures are beautiful things (and
not just for gliders).


Three reasons that may be significant are that:

1) The stabiliser is likely to be raised above the level of any crop
that the pilot may land in - therefore it will not be removed by
injudicious field-selection.

2) Also, I think I have read that a T-tail configuration produces one
less vortex than a conventional tail arrangement:- a vortex is spawned
from the end of each free tip of a tail surface (stabiliser or rudder)
therefore the top of the fin will not produce a vortex in a T-tail
arrangement (as the stabiliser prevents the fin from having a free
tip in the air stream). A vortex causes drag, therefore a T-tail will
be marginally more aerodynamically efficient.

3) Spin recovery is easier when the stabiliser is not in the
turbulence of a spinning main-plane - as is more likely to be the case
with a T-tail. Therefore a T-tail may be a safer aeroplane for
low-time pilots.



Jon.

(JonB) wrote in message om...
Marian Aldenhövel wrote in message ...
Hi,

I have noticed that most if not all modern gliders are built with a
T-Tail (not sure about the term, I am talking about the elevator being
located at the top of the tailfin). While most power-aircraft I know
right up to the airliners have it at the bottom.

What are the aerodynamic or constructive reasons for that?

Ciao, MM

To insure that your boom will snap during a groundloop, thereby
keeping our glass repair shops in buisness. (mass at the end of the
moment arm)
Seriously, I believe spin recovery and crop clearance to be the
primary reasons.
Why not a "V"? Ever flown a Bonanza in rough air? V's have a yaw-pitch
coupling that I find annoying.

-Dan