limit of trim = limit of travel?

wrote:
On May 8, 6:22 am, nospam wrote:

For those who were wondering about tab effect, or indeed elevator effect
on total tail lift the following may help;
Each item can be considered separately.
There will be a basic tail camber lift component which in many cases is
zero.
Then find the tailplane AOA and from the lift curve slope find tail Cl -
put that into the normal lift equation.
At that particular tailplane AOA, select the elevator AOA and again find
the Cl from the lift curve.
Then do the same for the tab.
Add the 3 solutions to get total tail lift.
Do this for the complete range of angle of attack for each component and
you will know the total range (and direction) of tail lift.
Cheers

Sorry, but each item can't be considered separately, any more
than an aileron can be designed or its effect determined without the
wing ahead of it. Removing the elevator from the stab, physically,
would make the stab almost useless, especially if it has an airfoil
shape and/or has aerodynamic balance. Working out numbers for an
elevator without considering the stab's effect on the camber and AOA
for the whole assembly is also useless. The air doesn't decide what
bits it will react to or ignore; it only sees an airfoil of some sort,
having at any given instant a particular camber and AOA, and the tab
is part of that assembly, whether deflected or not. The tab doesn't
contribute much, if any, to tail downforce, but does affect elevator
float position, and that elevator position sure does affect downforce.
Airplanes are not the sum of their parts. I wish it was that
simple.

Dan

Geeez I hadn't realized how thick you guys are.
Of course the tail, elevator and tab are taken into account - AOA tail
is wing AOA plus downwash, elevator AOA is wing AOA plus tail downwash
plus elevator angle, tab AOA is wing AOA plus wing downwash plus
tailplane wash plus elevator wash (at a particular elevator angle).
Your comments on elevator float position are irrelevant when one decides
to do calculations at a particular elevator angle. Float position is
nice to know for stick free stability measurements, but both the pilot
and the engineer can set the elevator angle at any they wish
irrespective of float.
If you really believe that aircraft are not the sum of the parts I would
suggest that any study of serious aerodynamic theory is probably beyond you.

References:
Duncan W. J. Control and Stability of Aircraft
Babister A. W. Aircraft Stability and Control
Perkins and Hage Airplane Performance Stability and Control

Get these out of your library you might actually learn something!
and
Course Notes Empire Test Pilot School.

The top 3 are widely used texts for aeronautical engineering degree courses.
I know I wrote I would not be back and I now realize that this group is
not one where serious informed discussion can be had.
I really won't be back.

On Wed, 7 May 2008 13:55:43 -0700 (PDT), WingFlaps
wrote:

On May 8, 12:17*am, Stealth Pilot
wrote:


your questions dont have that much depth btw.
just a lot of misunderstood aerodynamics.


Naysaying is the mark of a troll wihen no facts are given to back it
up.

Cheers

accusing someone who disagrees with you of being a troll is so lame.

ok lets get this in proper perspective.

the average GA tailplane has a span of about 8ft.
the trim tab sits on only one side and it is about a foot span and
maybe 2 inches chord.

just considering the tailplane chord through the trim tab for the time
being. you are looking at a chord of about 2 ft.
wound to it's full extent it would have maybe 5% effective change in
the aerofoil characteristics. bear in mind that it lives down near the
trailing edge where the contribution to lift is minimal.

so the overall effect is perhaps 5% of 1/8th of the tailplane.
calculate that out and the change of the characteristics overall is
something like 0.000625 or 0.06% change.

take into account the fact that trim tabs exist for all their life
near the centre of travel and so have minimal effect anyway and you
have wasted a huge amount of design time on the most trivial of red
herrings.

you dont need to consider the size of the trim tab in the early part
of a design at all.

in the interesting discussion you had with bertie all of his posts
were correct in pure theory terms but in overall actual effect you are
talking about a variation between an original 100% and 99.937% or
100.06% of the rest of the tailplane. ...which I why I think the
direction these discussions are heading is nonsense.

if you want to be at the top of the dog pile thats fine by me.
if you want to design good aeroplanes put the ego in the back pocket
and try building on the hundred years of knowledge built up by your
predecessors. you'll never learn until you accept that you need to
learn.

Stealth ( been studying and learning aviation for 37 years now ) Pilot

"nospam" wrote in message
news:PNydnSQ4QbdIurnVnZ2dnUVZ_j-dnZ2d@internode...


Geeez I hadn't realized how thick you guys are.
Of course the tail, elevator and tab are taken into account - AOA tail is
wing AOA plus downwash, elevator AOA is wing AOA plus tail downwash plus
elevator angle, tab AOA is wing AOA plus wing downwash plus tailplane wash
plus elevator wash (at a particular elevator angle). Your comments on
elevator float position are irrelevant when one decides to do calculations
at a particular elevator angle. Float position is nice to know for stick
free stability measurements, but both the pilot and the engineer can set
the elevator angle at any they wish irrespective of float.
If you really believe that aircraft are not the sum of the parts I would
suggest that any study of serious aerodynamic theory is probably beyond
you.

References:
Duncan W. J. Control and Stability of Aircraft
Babister A. W. Aircraft Stability and Control
Perkins and Hage Airplane Performance Stability and Control

Get these out of your library you might actually learn something!
and
Course Notes Empire Test Pilot School.

The top 3 are widely used texts for aeronautical engineering degree
courses.
I know I wrote I would not be back and I now realize that this group is
not one where serious informed discussion can be had.
I really won't be back.



Hey, don't let these to assholes run you off. There are a lot of good and
reasonable people around here. You just have to learn who to ignore, and you
just met two of the three most troubled children.

Stick around. Just don't answer these two from now on.

"Stealth Pilot" wrote in message
...
On Wed, 7 May 2008 13:55:43 -0700 (PDT), WingFlaps
wrote:

On May 8, 12:17 am, Stealth Pilot
wrote:


your questions dont have that much depth btw.
just a lot of misunderstood aerodynamics.


Naysaying is the mark of a troll wihen no facts are given to back it
up.

Cheers

accusing someone who disagrees with you of being a troll is so lame.


It's also the first thing a wanna be troll does.

On May 9, 4:30 am, nospam wrote:

Geeez I hadn't realized how thick you guys are.
Of course the tail, elevator and tab are taken into account -

And I quote you:

"They only work "together", as you put, after a lot of careful
engineering of the individual components and the interaction between
them."

"Each item can be considered separately."

The overall impression you give is that they have little to do with
each other and can be separated as if they will act as they do without
being attached to the other parts, which is false. Sorry if I took it
that way, but I think a lot of folks would read it exactly the same as
I did.
And Maxwell needs to go do dome reading, too. Endless flaming
only makes him look like a spoiled schoolyard bully.

Dan

"Maxwell" luv2^fly99@cox.^net wrote in news:FyOUj.2537$hJ1.2363
@newsfe17.lga:


"Bertie the Bunyip" wrote in message
...
I won't be lurking to read it.

Kay, see ya.


Bertie


Squirt, squirt there Squirty ****drip.


Yes, my little yellow friend.


Bertie

nospam wrote in
news:PNydnSQ4QbdIurnVnZ2dnUVZ_j-dnZ2d@internode:

wrote:
On May 8, 6:22 am, nospam wrote:

For those who were wondering about tab effect, or indeed elevator
effect on total tail lift the following may help;
Each item can be considered separately.
There will be a basic tail camber lift component which in many cases
is zero.
Then find the tailplane AOA and from the lift curve slope find tail
Cl - put that into the normal lift equation.
At that particular tailplane AOA, select the elevator AOA and again
find the Cl from the lift curve.
Then do the same for the tab.
Add the 3 solutions to get total tail lift.
Do this for the complete range of angle of attack for each component
and you will know the total range (and direction) of tail lift.
Cheers

Sorry, but each item can't be considered separately, any more
than an aileron can be designed or its effect determined without the
wing ahead of it. Removing the elevator from the stab, physically,
would make the stab almost useless, especially if it has an airfoil
shape and/or has aerodynamic balance. Working out numbers for an
elevator without considering the stab's effect on the camber and AOA
for the whole assembly is also useless. The air doesn't decide what
bits it will react to or ignore; it only sees an airfoil of some
sort, having at any given instant a particular camber and AOA, and
the tab is part of that assembly, whether deflected or not. The tab
doesn't contribute much, if any, to tail downforce, but does affect
elevator float position, and that elevator position sure does affect
downforce.
Airplanes are not the sum of their parts. I wish it was that
simple.

Dan

Geeez I hadn't realized how thick you guys are.
Of course the tail, elevator and tab are taken into account - AOA tail
is wing AOA plus downwash, elevator AOA is wing AOA plus tail downwash
plus elevator angle, tab AOA is wing AOA plus wing downwash plus
tailplane wash plus elevator wash (at a particular elevator angle).
Your comments on elevator float position are irrelevant when one
decides to do calculations at a particular elevator angle. Float
position is nice to know for stick free stability measurements, but
both the pilot and the engineer can set the elevator angle at any they
wish irrespective of float.
If you really believe that aircraft are not the sum of the parts I
would suggest that any study of serious aerodynamic theory is probably
beyond you.

References:
Duncan W. J. Control and Stability of Aircraft
Babister A. W. Aircraft Stability and Control
Perkins and Hage Airplane Performance Stability and Control

Get these out of your library you might actually learn something!


They don't appear to have done much for you..



Bertie

"Maxwell" luv2^fly99@cox.^net wrote in
:


"nospam" wrote in message
news:PNydnSQ4QbdIurnVnZ2dnUVZ_j-dnZ2d@internode...


Geeez I hadn't realized how thick you guys are.
Of course the tail, elevator and tab are taken into account - AOA
tail is wing AOA plus downwash, elevator AOA is wing AOA plus tail
downwash plus elevator angle, tab AOA is wing AOA plus wing downwash
plus tailplane wash plus elevator wash (at a particular elevator
angle). Your comments on elevator float position are irrelevant when
one decides to do calculations at a particular elevator angle. Float
position is nice to know for stick free stability measurements, but
both the pilot and the engineer can set the elevator angle at any
they wish irrespective of float. If you really believe that aircraft
are not the sum of the parts I would suggest that any study of
serious aerodynamic theory is probably beyond you.

References:
Duncan W. J. Control and Stability of Aircraft
Babister A. W. Aircraft Stability and Control
Perkins and Hage Airplane Performance Stability and Control

Get these out of your library you might actually learn something!
and
Course Notes Empire Test Pilot School.

The top 3 are widely used texts for aeronautical engineering degree
courses.
I know I wrote I would not be back and I now realize that this group
is not one where serious informed discussion can be had.
I really won't be back.



Hey, don't let these to assholes run you off. There are a lot of good
and reasonable people around here. You just have to learn who to
ignore, and you just met two of the three most troubled children.

Stick around. Just don't answer these two from now on.



Snort!


Bertie

"Maxwell" luv2^fly99@cox.^net wrote in news:cmXUj.2555$hJ1.1023
@newsfe17.lga:


"Stealth Pilot" wrote in message
...
On Wed, 7 May 2008 13:55:43 -0700 (PDT), WingFlaps
wrote:

On May 8, 12:17 am, Stealth Pilot
wrote:


your questions dont have that much depth btw.
just a lot of misunderstood aerodynamics.


Naysaying is the mark of a troll wihen no facts are given to back it
up.

Cheers

accusing someone who disagrees with you of being a troll is so lame.


It's also the first thing a wanna be troll does.




OK wannabe boi.


Bertie

On May 9, 11:57*pm, Stealth Pilot
wrote:
On Wed, 7 May 2008 13:55:43 -0700 (PDT), WingFlaps

wrote:
On May 8, 12:17*am, Stealth Pilot
wrote:

your questions dont have that much depth btw.
just a lot of misunderstood aerodynamics.

Naysaying is the mark of a troll wihen no facts are given to back it
up.

Cheers

accusing someone who disagrees with you of being a troll is so lame.

ok lets get this in proper perspective.

the average GA tailplane has a span of about 8ft.
the trim tab sits on only one side and it is about a foot span and
maybe 2 inches chord.


Go and measure an Arrow or 177. Even a 172 has a bigger trim tab than
that. BUT you still don't understand the point.

just considering the tailplane chord through the trim tab for the time
being. you are looking at a chord of about 2 ft. *
wound to it's full extent it would have maybe 5% effective change in
the aerofoil characteristics. bear in mind that it lives down near the
trailing edge where the contribution to lift is minimal.


With this last statement I can see there is absolutely no point to
discussing this with you as you don't know how an airfoil works.

Bye

.