Lancair Legacy Design Flaw?

"Bryan Martin" wrote in message
...
That could only happen if the plane was loaded with the CG way aft of
the limit. Otherwise, the plane would pitch DOWN if the stabilizer
stalled because the stabilizer normally produces a down force to keep
the nose up.



If it worked that way it would be a built-in safety factor helping to
forestall a stall of the main wing. But suppose the motor died and the
aircraft was then a glider. One must glide nose down. The horizontal
stabilizer forcing the nose down would then cause the pilot to pull back on
the stick to counteract the forces for aft. If the stabilizer stalled in
this attitude the nose is supposed to pitch down but would it? The tail
might just continue to drop provided the main wing still gets traction??? CG
is dependent upon both lifting both control surfaces as well as weight
distribution.
--
Gregory Hall


In article ,
"Gregory Hall" wrote:

http://www.youngeagles.org/photos/gallery/Monoplanes/LancairLegacy2000.jpg

Look at the picture. It's easy to see why the Lancair is dangerous. The
horizontal stabilizers appear to be on the too small side. This would
result
in their stalling before the wing. Then the aircraft would pitch up
making
the main wing stall. Ill-conceived, IMO.

A good lawyer needs to get on this with respect to BadWaterBill's
untimely
demise.

--
Gregory Hall

--
Bryan Martin
N61BM, CH 601 XL, Ram Subaru, Stratus redrive.

In article ,
"Gregory Hall" wrote:

"Bryan Martin" wrote in message
...
That could only happen if the plane was loaded with the CG way aft of
the limit. Otherwise, the plane would pitch DOWN if the stabilizer
stalled because the stabilizer normally produces a down force to keep
the nose up.



If it worked that way it would be a built-in safety factor helping to
forestall a stall of the main wing. But suppose the motor died and the
aircraft was then a glider. One must glide nose down. The horizontal
stabilizer forcing the nose down would then cause the pilot to pull back on
the stick to counteract the forces for aft. If the stabilizer stalled in
this attitude the nose is supposed to pitch down but would it? The tail
might just continue to drop provided the main wing still gets traction??? CG
is dependent upon both lifting both control surfaces as well as weight
distribution.

Sorry. But centre of *mass* (to use the correct term) is not in any way
dependent on the lift from anything.

The centre of mass is a parameter than is completely fixed by the
distribution of the mass of the aircraft's components. Whether any
surface is providing lift will not change it.

So as long as the main wing is located aft of the centre of mass, the
aircraft will pitch *down* when lift from the tail plane is lost.

Period.

--
Gregory Hall


In article ,
"Gregory Hall" wrote:

http://www.youngeagles.org/photos/ga...Legacy2000.jpg


Look at the picture. It's easy to see why the Lancair is dangerous. The
horizontal stabilizers appear to be on the too small side. This would
result
in their stalling before the wing. Then the aircraft would pitch up
making
the main wing stall. Ill-conceived, IMO.

A good lawyer needs to get on this with respect to BadWaterBill's
untimely
demise.

--
Gregory Hall

--
Bryan Martin
N61BM, CH 601 XL, Ram Subaru, Stratus redrive.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

On Oct 29, 11:46*am, Alan Baker wrote:
In article ,
*"Gregory Hall" wrote:



"Bryan Martin" wrote in message
...
That could only happen if the plane was loaded with the CG way aft of
the limit. Otherwise, the plane would pitch DOWN if the stabilizer
stalled because the stabilizer normally produces a down force to keep
the nose up.

If it worked that way it would be a built-in safety factor helping to
forestall a stall of the main wing. But suppose the motor died and the
aircraft was then a glider. One must glide nose down. The horizontal
stabilizer forcing the nose down would then cause the pilot to pull back on
the stick to counteract the forces for aft. If the stabilizer stalled in
this attitude the nose is supposed to pitch down but would it? The tail
might just continue to drop provided the main wing still gets traction??? CG
is dependent upon both lifting both control surfaces as well as weight
distribution.

Sorry. But centre of *mass* (to use the correct term) is not in any way
dependent on the lift from anything.

The centre of mass is a parameter than is completely fixed by the
distribution of the mass of the aircraft's components. Whether any
surface is providing lift will not change it.

So as long as the main wing is located aft of the centre of mass, the
aircraft will pitch *down* when lift from the tail plane is lost.

Period.



--
Gregory Hall

In article ,
"Gregory Hall" wrote:

http://www.youngeagles.org/photos/ga...ncairLegacy200...

Look at the picture. It's easy to see why the Lancair is dangerous. The
horizontal stabilizers appear to be on the too small side. This would
result
in their stalling before the wing. Then the aircraft would pitch up
making
the main wing stall. Ill-conceived, IMO.

A good lawyer needs to get on this with respect to BadWaterBill's
untimely
demise.

--
Gregory Hall

--
Bryan Martin
N61BM, CH 601 XL, Ram Subaru, Stratus redrive.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

It's kinda simple. Assuming the main wheels are under the wing and the
a/c still rests on those and the nose wheel then wings are aft of the
cg and the horizontal stabilisers are there for down force to keep the
nose up. Not sure what Gregory is banging on about here.

In article
,
JohnO wrote:

On Oct 29, 11:46*am, Alan Baker wrote:
In article ,
*"Gregory Hall" wrote:



"Bryan Martin" wrote in message
...
That could only happen if the plane was loaded with the CG way aft of
the limit. Otherwise, the plane would pitch DOWN if the stabilizer
stalled because the stabilizer normally produces a down force to keep
the nose up.

If it worked that way it would be a built-in safety factor helping to
forestall a stall of the main wing. But suppose the motor died and the
aircraft was then a glider. One must glide nose down. The horizontal
stabilizer forcing the nose down would then cause the pilot to pull back
on
the stick to counteract the forces for aft. If the stabilizer stalled in
this attitude the nose is supposed to pitch down but would it? The tail
might just continue to drop provided the main wing still gets traction???
CG
is dependent upon both lifting both control surfaces as well as weight
distribution.

Sorry. But centre of *mass* (to use the correct term) is not in any way
dependent on the lift from anything.

The centre of mass is a parameter than is completely fixed by the
distribution of the mass of the aircraft's components. Whether any
surface is providing lift will not change it.

So as long as the main wing is located aft of the centre of mass, the
aircraft will pitch *down* when lift from the tail plane is lost.

Period.
snip

It's kinda simple. Assuming the main wheels are under the wing and the
a/c still rests on those and the nose wheel then wings are aft of the
cg and the horizontal stabilisers are there for down force to keep the
nose up. Not sure what Gregory is banging on about here.

Well, it's not quite *that* simple. There's no rule that the wheels need
to be directly under the centre of lift of the wing, but yeah...
....basically that's it.

I have no idea how anyone can get the wrong headed idea that the centre
of mass of a rigid body can move around.

--
Alan Baker
Vancouver, British Columbia
http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg

If it worked that way it would be a built-in safety factor helping to
forestall a stall of the main wing. But suppose the motor died and the
aircraft was then a glider. One must glide nose down. The horizontal
stabilizer forcing the nose down would then cause the pilot to pull back on
the stick to counteract the forces for aft. If the stabilizer stalled in
this attitude the nose is supposed to pitch down but would it? The tail
might just continue to drop provided the main wing still gets traction??? CG
is dependent upon both lifting both control surfaces as well as weight
distribution.
--
Gregory Hall


You seem to have the forces on the horizontal stabilizer backwards. The
force on the horizontal is down, (NOT up as with the main wing) which is
why an aircraft is stable in pitch unless improper loading places the CG
too far aft.

Of course, non of this applies to canard designs, which the Lancair is not.

Rip

On Tue, 28 Oct 2008 17:12:50 -0400, Gregory Hall wrote:

CG
is dependent upon both lifting both control surfaces as well as weight
distribution.

Thankfully that isn't the case otherwise you would have horrendous times
with energy management, for instance, with an ever evolving mass.