Lancair Legacy Design Flaw?

In article
,
BobR wrote:

On Nov 2, 5:56*pm, Alan Baker wrote:
In article
,

*BobR wrote:

snip





snip

Oh for gawd sake, you are talking about two totally
different
designs
and the aerodynamics of the two are totally different.
*The
Lancair
is
NOT a pusher and the engine is mounted forward of the CG
instead
of
on
top of it. *When the engine quits it will not pitch
upward.
*The
plane
you flew had the engine well above the center of gravity
with
a
pusher
prop and as a result produced a force that pushed the
nose of
the
aircraft down. *The two planes would not act pretty much
the
same
at
all. *The weight of the engine on the Legacy is forward
of
the CG
and
as a result always pulling the nose of the plane down.
*The
counter
to
the nose down is the horizontal stabilizer and the
elevator.
*Look at
the angle of incedence on the Horizontal Stabilizer and
you
will
find
a slight downward angle, not an upward angle as is common
on
the
wing. *This counteracts the force from the weight of the
engine.
*An
engine out condition will not have a significant effect
on
pitch
until
the airspeed changes and that will result in a nose down,
not
nose up
pull.

The one thing not quite right is that there is no important
difference
between tractor vs. pusher configurations with respect to
directional
stability.

Not sure what you are replying to but I never said anything
about
directional stability. *The discussion was regarding pitch
forces.

Which is essentially the same thing.

Pusher or puller doesn't affect pitch forces. What affects
pitch
forces
is the length of the moment arm between the centre of mass and
the
thrust line.

Like some of the early rocket designers (e.g. Goddard), you
are
falling
into the fallacy that somehow pulling is more stable than
pushing.
This
is not so.

- Show quoted text -

Again Alan, I never indicated any issue with pusher vs tractor.
*The
layout of the two planes being discussed is totally different.
*One
involved a tractor configuration with the thrust line being very
near
the vertical center of gravity. *The second involved an plane
with
the
engine mounted on a pylon with a thrust line well above the
vertical
center of gravity. *This configuration, rather it be a tractor or
pusher will induce nose down forces that must be countered by the
horizontal stabilizer with an upward force. *This is contrary to
the
standard configuration which requires a downward force to counter
the
weight of the engine. *The post I was replying to was trying to
link
the characteristic of the pylon mounted configuration to the
Legacy.

Sorry, man, but you made specific reference to the plane being a
pusher
as if it was a relevant factor:

"The Lancair is NOT a pusher and the engine is mounted forward of
the
CG
instead of on top of it. *When the engine quits it will not pitch
upward. *The plane you flew had the engine well above the center of
gravity with a pusher prop and as a result produced a force that
pushed
the nose of the aircraft down."

When you include extraneous details, you make the essence of the
situation harder to glean.

And you're doing it again. You're conflating thrust line induced
pitch
changes with weight of engine. One is changing, one is constant.

The only part that you had to talk about was the fact that the
thrust
line was significantly above the centre of mass. The weight of the
engine doesn't matter (in an aircraft that has it's centre of
gravity
appropriately located), nor does pusher vs. puller.

- Show quoted text -

Well excuse the holy hell out of me for not phrasing things the way
you want it. *My references were based on the specifics of the two
planes involved in the discussion and if you can't gleem that fact
from it, too ****ing bad.

Trying to retcon your comments and say that such and such wasn't what
you meant would work better if you...

I said what I ment but I can't help that you read into it something
else.

And you made the fact that the aircraft was a pusher an issue.

You were wrong. Deal with it.


No, I never made the fact that the aircraft was a pusher into an
issue...YOU DID. I simply pointed out different design elements of
the two aircraft. You drew false conclusions from them and now try to
make a issue from them.

Sigh....

"The Lancair is NOT a pusher..."



...ACTUALLY SHOWED YOU UNDERSTOOD WHAT YOU'RE TALKING ABOUT...

I knew exactly what I was talking about but again, you read something
into it beyond what I said. *That part is your problem not mine.

Nope. Because the weight of an engine has precisely the same influence
on the aircraft at all times, operating or not.



Gee do tell! Again you make false assumptions and then try and make
some point from it.

Sigh...

"This is contrary to the standard configuration which requires a
downward force to counter the weight of the engine."

That's you attributing the engine's weight some special status when in
the nose, when if fact, it is the overall position of the centre of
gravity that matters.



...in your next post.

You, OTOH, showed you still didn't get it and now you're getting ****y.

I am getting very tired of your arrogant attitude that ONLY YOU
understand.

Not "only me", just -- quite obviously -- not you.



And the word your tiny little mind was scratching for was "glean".

Sorry but my typing isn't always the greatest and once again, your
arrogance shows in thinking you are the only smart one in the group.

Sorry, (and note the correct use of the comma, BTW) but the error wasn't
a typo, and you can't retcon it into one.


Yep, once again your arrogance rises to the occasion.

My ability to understand that typing "gleem" when the word you're
looking for is "glean" can't be a typo is "arrogance", now?




Always happy to help the ignorant.

Gee, so nice of you to come down from that tower you put yourself into
and mingle with us common folk.

Hey...

You're more common than most.


And you are a lot more arrogant than most. Looking back through your
posts it was clear that you felt the necessity to correct just about
everyone. Guess that puts me in the good company of a lot of other
common folk.

I correct things that are incorrect. Unlike you: who introduces
extraneous and erroneous points into a discussion, thus clouding the
issue.

The only thing that matter was thrust line. You kept introducing other
factors that were irrelevant.

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

On Nov 2, 8:22*pm, Alan Baker wrote:
In article
,

*BobR wrote:
On Nov 2, 5:56*pm, Alan Baker wrote:
In article
,

*BobR wrote:

snip

snip





Oh for gawd sake, you are talking about two totally
different
designs
and the aerodynamics of the two are totally different.

Alan Baker wrote:
The only thing that matter was thrust line.

You've managed to make the same incorrect claim at least twice (that I've
counted) in one thread. Are you sure you aren't overlooking something?

In article
,
BobR wrote:

On Nov 2, 8:22*pm, Alan Baker wrote:
In article
,

*BobR wrote:
On Nov 2, 5:56*pm, Alan Baker wrote:
In article
,

*BobR wrote:

snip

snip





Oh for gawd sake, you are talking about two totally
different
designs
and the aerodynamics of the two are totally
different.
*The
Lancair
is
NOT a pusher and the engine is mounted forward of the
CG
instead
of
on
top of it. *When the engine quits it will not pitch
upward.
*The
plane
you flew had the engine well above the center of
gravity
with
a
pusher
prop and as a result produced a force that pushed the
nose of
the
aircraft down. *The two planes would not act pretty
much
the
same
at
all. *The weight of the engine on the Legacy is
forward
of
the CG
and
as a result always pulling the nose of the plane
down.
*The
counter
to
the nose down is the horizontal stabilizer and the
elevator.
*Look at
the angle of incedence on the Horizontal Stabilizer
and
you
will
find
a slight downward angle, not an upward angle as is
common
on
the
wing. *This counteracts the force from the weight of
the
engine.
*An
engine out condition will not have a significant
effect
on
pitch
until
the airspeed changes and that will result in a nose
down,
not
nose up
pull.

The one thing not quite right is that there is no
important
difference
between tractor vs. pusher configurations with respect
to
directional
stability.

Not sure what you are replying to but I never said
anything
about
directional stability. *The discussion was regarding
pitch
forces.

Which is essentially the same thing.

Pusher or puller doesn't affect pitch forces. What affects
pitch
forces
is the length of the moment arm between the centre of mass
and
the
thrust line.

Like some of the early rocket designers (e.g. Goddard),
you
are
falling
into the fallacy that somehow pulling is more stable
than
pushing.
This
is not so.

- Show quoted text -

Again Alan, I never indicated any issue with pusher vs
tractor.
*The
layout of the two planes being discussed is totally
different.
*One
involved a tractor configuration with the thrust line being
very
near
the vertical center of gravity. *The second involved an plane
with
the
engine mounted on a pylon with a thrust line well above the
vertical
center of gravity. *This configuration, rather it be a
tractor or
pusher will induce nose down forces that must be countered by
the
horizontal stabilizer with an upward force. *This is contrary
to
the
standard configuration which requires a downward force to
counter
the
weight of the engine. *The post I was replying to was trying
to
link
the characteristic of the pylon mounted configuration to the
Legacy.

Sorry, man, but you made specific reference to the plane being
a
pusher
as if it was a relevant factor:

"The Lancair is NOT a pusher and the engine is mounted forward
of
the
CG
instead of on top of it. *When the engine quits it will not
pitch
upward. *The plane you flew had the engine well above the
center of
gravity with a pusher prop and as a result produced a force
that
pushed
the nose of the aircraft down."

When you include extraneous details, you make the essence of
the
situation harder to glean.

And you're doing it again. You're conflating thrust line
induced
pitch
changes with weight of engine. One is changing, one is
constant.

The only part that you had to talk about was the fact that the
thrust
line was significantly above the centre of mass. The weight of
the
engine doesn't matter (in an aircraft that has it's centre of
gravity
appropriately located), nor does pusher vs. puller.

- Show quoted text -

Well excuse the holy hell out of me for not phrasing things the
way
you want it. *My references were based on the specifics of the
two
planes involved in the discussion and if you can't gleem that
fact
from it, too ****ing bad.

Trying to retcon your comments and say that such and such wasn't
what
you meant would work better if you...

I said what I ment but I can't help that you read into it something
else.

And you made the fact that the aircraft was a pusher an issue.

You were wrong. Deal with it.

No, I never made the fact that the aircraft was a pusher into an
issue...YOU DID. *I simply pointed out different design elements of
the two aircraft. *You drew false conclusions from them and now try to
make a issue from them.

Sigh....

"The Lancair is NOT a pusher..."


AND THAT IS WHERE YOU MIND WENT BLANK AND YOU STOPPED COMPREHENDING
ANYTHING ELSE.

Nope.

I comprehended the rest fine.

You, OTOH, led of your reply with what you now claim was an
irrelevancy...




...ACTUALLY SHOWED YOU UNDERSTOOD WHAT YOU'RE TALKING ABOUT...

I knew exactly what I was talking about but again, you read something
into it beyond what I said. *That part is your problem not mine.

Nope. Because the weight of an engine has precisely the same influence
on the aircraft at all times, operating or not.

Gee do tell! *Again you make false assumptions and then try and make
some point from it.

Sigh...

"This is contrary to the standard configuration which requires a
downward force to counter the weight of the engine."

That's you attributing the engine's weight some special status when in
the nose, when if fact, it is the overall position of the centre of
gravity that matters.


Yep, the fact that it is FORWARD of the CG doesn't matter at all.
Damn but you can't seem to understand anything that is not said
exactly like you want it to be. Take one part out of context and try
and make an entire argument from it.

Precisely correct. The fact that it is forward of the centre of *mass*
doesn't matter at all, because whatever the location of the engine, its
effect is the same whether its operating or not.



...in your next post.

You, OTOH, showed you still didn't get it and now you're getting
****y.

I am getting very tired of your arrogant attitude that ONLY YOU
understand.

Not "only me", just -- quite obviously -- not you.

And the word your tiny little mind was scratching for was "glean".

Sorry but my typing isn't always the greatest and once again, your
arrogance shows in thinking you are the only smart one in the group.

Sorry, (and note the correct use of the comma, BTW) but the error
wasn't
a typo, and you can't retcon it into one.

Yep, once again your arrogance rises to the occasion.

My ability to understand that typing "gleem" when the word you're
looking for is "glean" can't be a typo is "arrogance", now?


So I didn't spell the word correctly...big fking deal. You want to be
my english teacher now too? The arrogance is that you couldn't help
yourself and had to make an issue of that too.

But you didn't claim it was a spelling error. You claimed it was a
typo...



Always happy to help the ignorant.

Gee, so nice of you to come down from that tower you put yourself
into
and mingle with us common folk.

Hey...

You're more common than most.

And you are a lot more arrogant than most. *Looking back through your
posts it was clear that you felt the necessity to correct just about
everyone. *Guess that puts me in the good company of a lot of other
common folk.

I correct things that are incorrect. Unlike you: who introduces
extraneous and erroneous points into a discussion, thus clouding the
issue.


No, you make issues where there were no issues and your arrogance
doesn't allow any one else room to say anything. You had to pick
apart my response without even trying to understand the point I was
trying to get across. You still don't get it and never will. You did
the same to everyone else who responded as well.

Sorry, but no. You make issues out of hwat (BTW, *that* is what a typo
looks like) are not issues.


The only thing that matter was thrust line. You kept introducing other
factors that were irrelevant.


That was clearly the only thing YOU BELIEVED mattered and clearly I
didn't say it exactly the way you wanted. TOO BAD! Yes, in this
particular case, the thrust line was important and I indicated such
but not in those words. But what I was more interested in was
pointing out that the two planes had totally different configurations
and would react differently. You can't and will never accept that
because you can't get beyond your own intrepretations an insist on
talking down to everybody.

The thrust line was *all* that was important in this discussion. And
clearly, you still don't understand that.

The only difference in their configuration that matter in the case of
loss of engine power was where the thrust line was in relation to the
centre of mass. The whole pusher/puller and position of the engine's
weight were completely irrelevant.

Simple fact, and I'm sorry you can't get it.


So at this point, I will simply yield to your superior knowledge of
all things and say that you are always right. From this point on I
will not try to make any posts unless you proof read them first. I
will also encourage everyone else to do the same.

Great. The group will be better off for it.

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

In article ,
Jim Logajan wrote:

Alan Baker wrote:
The only thing that matter was thrust line.

You've managed to make the same incorrect claim at least twice (that I've
counted) in one thread. Are you sure you aren't overlooking something?

I'm will to entertain that possibility.

What do you think I'm overlooking?

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

Alan Baker wrote:
In article ,
Jim Logajan wrote:

Alan Baker wrote:
The only thing that matter was thrust line.

You've managed to make the same incorrect claim at least twice (that
I've counted) in one thread. Are you sure you aren't overlooking
something?

I'm will to entertain that possibility.

What do you think I'm overlooking?

That the aircraft are moving through a fluid, not a vacuum.

So things like propwash affect a tractor differently than a pusher. In my
own analysis of the two types and their engine on versus engine off
dynamics, the thrust line has not been "the only thing that matter[s]." It
is more complex, and the texts I have handy do not make the situation
appear as simple as you claim.

If thrust line moment arm (relative to the c.g.) were all that mattered,
then the following two bottle rocket firework designs would fly the same
paths, mass, impulse curve, c.g., and thrust moment arm being held the
same:

(A) ----------------+-----+
|=====]

(B) +-----+----------------
|=====]

The attachments to the sticks are made so that the moment arms relative to
the c.g. are otherwise identical, but in (B) the thrust is opposite its
usual direction. Now in a vacuum I would expect them to fly the same paths
and would be surprised if they didn't do that. But in a fluid like the
atmosphere? Would you expect them to fly the same or different paths?
Frankly, I would be surprised if they did fly the same - but as I don't
have any fireworks handy at the moment I haven't gone outside to have fun,
er, run experiments to observe their behavior.

In article ,
Jim Logajan wrote:

Alan Baker wrote:
In article ,
Jim Logajan wrote:

Alan Baker wrote:
The only thing that matter was thrust line.

You've managed to make the same incorrect claim at least twice (that
I've counted) in one thread. Are you sure you aren't overlooking
something?

I'm will to entertain that possibility.

What do you think I'm overlooking?

That the aircraft are moving through a fluid, not a vacuum.

So things like propwash affect a tractor differently than a pusher. In my
own analysis of the two types and their engine on versus engine off
dynamics, the thrust line has not been "the only thing that matter[s]." It
is more complex, and the texts I have handy do not make the situation
appear as simple as you claim.

If thrust line moment arm (relative to the c.g.) were all that mattered,
then the following two bottle rocket firework designs would fly the same
paths, mass, impulse curve, c.g., and thrust moment arm being held the
same:

(A) ----------------+-----+
|=====]

(B) +-----+----------------
|=====]

The attachments to the sticks are made so that the moment arms relative to
the c.g. are otherwise identical, but in (B) the thrust is opposite its
usual direction. Now in a vacuum I would expect them to fly the same paths
and would be surprised if they didn't do that. But in a fluid like the
atmosphere? Would you expect them to fly the same or different paths?
Frankly, I would be surprised if they did fly the same - but as I don't
have any fireworks handy at the moment I haven't gone outside to have fun,
er, run experiments to observe their behavior.

Sorry, but you're proceeding from two wrong assumptions.

1. Your A and B examples would both behave the same in flight if their
centres of mass were both the same. It is the aerodynamic centre of
pressure moving ahead of the centre of mass that would cause B to be
unstable and A stable, if we operate from the assumption that the only
parts involved are the rocket and the stick.

2. In specific, both of the aircraft in this case are stable. They are
both stable because the aerodynamic centre of pressure is behind the
centre of mass and because the centre of lift of the main wing is behind
the centre of gravity. Thus, your assumption that a change in the
engines location matters is based on the erroneous assumption that such
a change is being made in isolation.

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

Alan Baker wrote:
Jim Logajan wrote:
Alan Baker wrote:
Jim Logajan wrote:
Alan Baker wrote:
The only thing that matter was thrust line.

You've managed to make the same incorrect claim at least twice
(that I've counted) in one thread. Are you sure you aren't
overlooking something?

I'm will to entertain that possibility.

What do you think I'm overlooking?

That the aircraft are moving through a fluid, not a vacuum.

So things like propwash affect a tractor differently than a pusher.
In my own analysis of the two types and their engine on versus engine
off dynamics, the thrust line has not been "the only thing that
matter[s]." It is more complex, and the texts I have handy do not
make the situation appear as simple as you claim.

If thrust line moment arm (relative to the c.g.) were all that
mattered, then the following two bottle rocket firework designs would
fly the same paths, mass, impulse curve, c.g., and thrust moment arm
being held the same:

(A) ----------------+-----+
|=====]

(B) +-----+----------------
|=====]

The attachments to the sticks are made so that the moment arms
relative to the c.g. are otherwise identical, but in (B) the thrust
is opposite its usual direction. Now in a vacuum I would expect them
to fly the same paths and would be surprised if they didn't do that.
But in a fluid like the atmosphere? Would you expect them to fly the
same or different paths? Frankly, I would be surprised if they did
fly the same - but as I don't have any fireworks handy at the moment
I haven't gone outside to have fun, er, run experiments to observe
their behavior.

Sorry, but you're proceeding from two wrong assumptions.

There is no dispute on your two points below. I'm glad to see you
understand about dynamic pressure - it was not evident (to me at least)
in your earlier posts. The problem still remains that your claim that the
"only thing that matter[s] was thrust line" is incompatible with the
aerodynamic differences between a tractor and pusher. You either read
past my second sentence "So things like propwash..." and it didn't
register or you did read it but still don't understand what you
"overlooked."

So here is again (in expanded form) what I think you overlooked:

Because tractor propwash generates forces on any aircraft surfaces in its
wake, so far as I know, no amount of thrust line adjustment can ever
eliminate the flight character differences between tractor and pusher
airplanes.

1. Your A and B examples would both behave the same in flight if their
centres of mass were both the same. It is the aerodynamic centre of
pressure moving ahead of the centre of mass that would cause B to be
unstable and A stable, if we operate from the assumption that the only
parts involved are the rocket and the stick.

2. In specific, both of the aircraft in this case are stable. They are
both stable because the aerodynamic centre of pressure is behind the
centre of mass and because the centre of lift of the main wing is
behind the centre of gravity. Thus, your assumption that a change in
the engines location matters is based on the erroneous assumption that
such a change is being made in isolation.

"Gregory Hall" wrote in message
...

I think it makes good sense. Look at the size of that engine up front.
Looks
like a P-51 Mustang for pity sake. When you're being pulled along by that
big prop and heavy, powerful engine it pulls the nose of the aircraft
down. The horizontal stabilizers have to counteract this force by putting
an upward force on the nose by pushing the tail down. If and when the
engine suddenly dies the aircraft will pitch up suddenly and since the
size of the stabilizers are so puny they might easily stall and be unable
to counteract the upward pitch at the nose resulting in a tail down death
spiral.

By the way, the Lancair Legacy is the most fun civilian airplane I've
flown and is the main reason I returned to general aviation after a
decades-long absence. I'm sure there is a Legacy near you and I'll bet
its pilot would be happy to take you for a ride. You can see for
yourself what a great airplane it is.

It looks too much like an irresponsible, hot rod, stunt plane to me. Is it
any wonder so many companies offering homebuilt aircraft have gone out of
business?

http://www.homebuilt.org/aircraft/nolonger.html

This is the safest homebuilt IMO.(VariEze ). The canard makes it
foolproof.

http://video.google.com.au/videoplay...77166441&hl=en

--
Gregory Hall


Gregory,

You have managed to prove quite indisputably to the entire group that you
really do not know the first thing about
aerodynamics or aircraft design.

You are totally and incontrovertibly wrong.

By the way, the canard does NOT make it foolproof. As a matter of fact I
recall Burt running up and down the runway
in an old beater car with his windtunnel models mounted on it, getting the
data he needed to make the canard arrangement
he used on several designs safe. It is much easier to design a safe
airplane with a conventional tail.

The Lancair Legacy has very light and quick response to the controls. That
makes an airplane FUN to fly. Especially
if you are a good pilot, and BWB was a good pilot. I flew with him in his
RV-6 at Pinckneyville the year he brought it
to the Pinckneyville Flyin.

The problem with an airplane like the Lancair occurs when the **** hits the
fan at low altitude. The airplane responds
quickly and it is fast. A momentary distraction can allow a considerable
unplanned excursion. If something relatively
immoveable intrudes itself into your flight path during that unplanned
excursion bad **** can happen. I believe bad ****
did in this case. Obviously unusual things were going on. Stuff was
drooling out of the airplane.

I am not going to guess what happened. There was an accident. I lost
another friend. I have lost too many friends that
way over the years. Janice is recovering. Slowly. Painfully. Bill did
not. We disagreed about many things over the
years. Some of them were, I am sure, due to failures in communication or
misunderstandings. That happens. I will
miss his sorry ass.

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

"Steve Hix" wrote in message
...
In article
,
Alan Baker wrote:

You have to take moments about something that isn't going to shift,
Steve. Centre of mass.


Steve replied ...

I know that that doesn't change (ignoring fuel burn), but things like
flaps' contribution to drag moments changes with changes in
configuration.

Else we'd never see pitch changes as we raise or lower the flaps, or
changes in speed as landing gear are retracted or extended.

Semantics can really make things confused. In aerodynamics and aircraft
design we simplify things to make the
math a bit easier. Instead of dealing with forces that move all over the
place and make it difficult to superimpose
mathematically to calculate their resolution and the resultant vectors which
would get relatively intractable, we
pick a point more or less at random and say "The force acts HERE!" Then we
figure out the moments about that
point contributed by our other factors. Then we merely sum up the moments,
using the appropriate arithmetic for
summing up vectors of course, and determine the resultant forces relatively
easily. To make this simplification
work we need to pick arbitrary points that don't move around. Things like
the "center of mass", or the "center of
lateral area", or the "center of gravity", or the "quarter chord line of the
lifting surface" and then we find how the
moments change about that point. We can even play additional simplification
games and normalize the actual moments
into a dimensionless coeficcient. If you look at a plot of the forces on a
wing you will see alongside the lift/drag
polar, another line labeled "moment coefficient." This moment coefficient
tells you how the center of lift moves about
relative to the quarter chord line of the wing. The neat thing about the
NACA 23012 airfoil section is the moment
coefficient is approximately zero throughout the normal angle of attack
range. This means the center of lift doesn't move
around very much on the wing. This is what made possible the monospar wing
on the DC-3! :-)

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )