spoilers vs. ailerons

"Skywise" wrote in message
...
[...]
This isn't true. Spoilers provide effective roll control even on a
stalled wing while ailerons do not. lift does not disappear when the
wing stalls.

Not so, Mike. Spoilers spoil lift. You can't spoil lift that ain't
there
as in a stalled wing.

But is not the definition of a stalled wing one that is
producing less lift than necessary to maintain flight?

Actually, the definition of a stalled wing is one that has exceeded the
critical angle of attack. The critical angle of attack is the point at
which the wing has the greatest lift coefficient.

It is true that a stalled wing still has lift, and it is also true that a
stalled wing can be provided with *some* roll control with spoilers, when in
the same situation ailerons would be useless.

I might dispute the use of the word "effective", just because often it's
used to imply some semblance of quality. But I think in this context, as
long as it's understood that "effective" simply means that the spoiler do
have an effect, there's no need for debating those semantics.

Pete

A stalled wing is still producing lift.

Mike
MU-2


"Darrell S" wrote in message
news:NrVFe.51930$4o.23949@fed1read06...
Mike Rapoport wrote:
"Darrell S" wrote in message
news:BavFe.49931$4o.24620@fed1read06...
wrote:
. With a spoiler controlled aircraft, when
you stall the wings it makes the spoiler ineffective. It can no
longer spoil lift that is no longer there. --

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

This isn't true. Spoilers provide effective roll control even on a
stalled wing while ailerons do not. lift does not disappear when the
wing stalls.
Mike
MU-2

Not so, Mike. Spoilers spoil lift. You can't spoil lift that ain't there
as in a stalled wing.

--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

"Peter Duniho" wrote in message
...
"Skywise" wrote in message
...
[...]
This isn't true. Spoilers provide effective roll control even on a
stalled wing while ailerons do not. lift does not disappear when the
wing stalls.

Not so, Mike. Spoilers spoil lift. You can't spoil lift that ain't
there
as in a stalled wing.

But is not the definition of a stalled wing one that is
producing less lift than necessary to maintain flight?

Actually, the definition of a stalled wing is one that has exceeded the
critical angle of attack. The critical angle of attack is the point at
which the wing has the greatest lift coefficient.

It is true that a stalled wing still has lift, and it is also true that a
stalled wing can be provided with *some* roll control with spoilers, when
in the same situation ailerons would be useless.

I might dispute the use of the word "effective", just because often it's
used to imply some semblance of quality. But I think in this context, as
long as it's understood that "effective" simply means that the spoiler do
have an effect, there's no need for debating those semantics.


In the MU-2 roll control is pretty good in a stall. It takes more yoke
movement to get the same effect but control is still very positive.

Mike
MU-2

That's a key statement. The definition of stalled, as the FAA and the pilot
see it, is not an aerodynamic definition. It is a definition based on
aircraft
handling and controllability.

Nobody here has yet defined spoiler or aileron either. If the "spoilers" are
located far aft on the wing, and are hinged at their leading edge, would
you call them ailerons? How about if the ailerons go up only, are they
spoilers? There are plug type spoilers, hinged at the leading edge spoilers,
vented spoilers, spoilers at the front of the airfoil, spoilers at the rear
of the
airfoil, spoilers in the slot between the wing and flap and the variations
go on
and on. Their characteristics vary widely. There are lots of reports done a
long time ago by NACA on spoilers. One of the characteristics I remember
reading from these reports was the location on the airfoil was a compromise
between control response delay and control effect. Forward locations had
more effect and more delay. Aft locations went the other way. The conclusion
I came to was that the best location and size to have the good
characteristics
of ailerons was the same size and location as ailerons.

The Mead Adventure started life with spoilers, no ailerons. The Durand Mark
II
biplane had full span spoilers on the lower (forward) wing, no ailerons. The
Adventure was converted to ailerons very quickly. The spoilers were quite
unacceptable, located forward on the airfoil. The Durand biplane worked
quite
well according to Bill Durand. As I recall, they were located aft on the
airfoil, in
front of plain flaps. I once flew an R/C model specifically to test
spoilers in
combination with full span flaps. The spoilers were part of the flap gap
area, so
that the optimum lift over the flap would be destroyed with spoiler
deflection. We
started the testing by taping a spoiler to one wing of an existing
aircraft. When it
took about half aileron to fly level, we quit changing the size and
deflection of the
temporary taped-on spoiler, knowing that a wing with similarly sized
spoilers
would be controllable enough to fly (no flaps). After I completed the wing
(we used
the same aircraft that we used to test the taped-on spoilers), I estimated
that
control response should be the most similar to ailerons with the flaps down
about
10 to 20 degrees. This turned out to be right on the button. With flaps up,
the roll
rate was considerably slower than with ailerons. With flaps full down, the
roll rate
was extremely high. So much so that only a couple of landings were
attempted.
With the flaps up, roll response was just adequate both INVERTED and
upright.
Kind of neat seeing an aircraft with spoilers instead of ailerons make a
low inverted
pass. BTW, this was done around 1970. I still have the wing. Never
crashed.

My conclusion was that spoilers make good spoilers, ailerons make good
ailerons
and flaps make good flaps.


Mike Rapoport wrote in message ...
A stalled wing is still producing lift.

Mike
MU-2


"Darrell S" wrote in message
news:NrVFe.51930$4o.23949@fed1read06...
Mike Rapoport wrote:
"Darrell S" wrote in message
news:BavFe.49931$4o.24620@fed1read06...
wrote:
. With a spoiler controlled aircraft, when
you stall the wings it makes the spoiler ineffective. It can no
longer spoil lift that is no longer there. --

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

This isn't true. Spoilers provide effective roll control even on a
stalled wing while ailerons do not. lift does not disappear when the
wing stalls.
Mike
MU-2

Not so, Mike. Spoilers spoil lift. You can't spoil lift that ain't
there
as in a stalled wing.

--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

Well it is certainly possible to screw up the design of anything. However I
stick to my orginal premise that spoilers (as installed in a properly
designed aircraft) have far superior roll response at low speed and vastly
better roll response when the wing is stalled.

Mike
MU-2


" wrote in message
...
That's a key statement. The definition of stalled, as the FAA and the
pilot
see it, is not an aerodynamic definition. It is a definition based on
aircraft
handling and controllability.

Nobody here has yet defined spoiler or aileron either. If the "spoilers"
are
located far aft on the wing, and are hinged at their leading edge, would
you call them ailerons? How about if the ailerons go up only, are they
spoilers? There are plug type spoilers, hinged at the leading edge
spoilers,
vented spoilers, spoilers at the front of the airfoil, spoilers at the
rear
of the
airfoil, spoilers in the slot between the wing and flap and the variations
go on
and on. Their characteristics vary widely. There are lots of reports done
a
long time ago by NACA on spoilers. One of the characteristics I remember
reading from these reports was the location on the airfoil was a
compromise
between control response delay and control effect. Forward locations had
more effect and more delay. Aft locations went the other way. The
conclusion
I came to was that the best location and size to have the good
characteristics
of ailerons was the same size and location as ailerons.

The Mead Adventure started life with spoilers, no ailerons. The Durand
Mark
II
biplane had full span spoilers on the lower (forward) wing, no ailerons.
The
Adventure was converted to ailerons very quickly. The spoilers were quite
unacceptable, located forward on the airfoil. The Durand biplane worked
quite
well according to Bill Durand. As I recall, they were located aft on the
airfoil, in
front of plain flaps. I once flew an R/C model specifically to test
spoilers in
combination with full span flaps. The spoilers were part of the flap gap
area, so
that the optimum lift over the flap would be destroyed with spoiler
deflection. We
started the testing by taping a spoiler to one wing of an existing
aircraft. When it
took about half aileron to fly level, we quit changing the size and
deflection of the
temporary taped-on spoiler, knowing that a wing with similarly sized
spoilers
would be controllable enough to fly (no flaps). After I completed the wing
(we used
the same aircraft that we used to test the taped-on spoilers), I estimated
that
control response should be the most similar to ailerons with the flaps
down
about
10 to 20 degrees. This turned out to be right on the button. With flaps
up,
the roll
rate was considerably slower than with ailerons. With flaps full down, the
roll rate
was extremely high. So much so that only a couple of landings were
attempted.
With the flaps up, roll response was just adequate both INVERTED and
upright.
Kind of neat seeing an aircraft with spoilers instead of ailerons make a
low inverted
pass. BTW, this was done around 1970. I still have the wing. Never
crashed.

My conclusion was that spoilers make good spoilers, ailerons make good
ailerons
and flaps make good flaps.


Mike Rapoport wrote in message ...
A stalled wing is still producing lift.

Mike
MU-2


"Darrell S" wrote in message
news:NrVFe.51930$4o.23949@fed1read06...
Mike Rapoport wrote:
"Darrell S" wrote in message
news:BavFe.49931$4o.24620@fed1read06...
wrote:
. With a spoiler controlled aircraft, when
you stall the wings it makes the spoiler ineffective. It can no
longer spoil lift that is no longer there. --

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

This isn't true. Spoilers provide effective roll control even on a
stalled wing while ailerons do not. lift does not disappear when the
wing stalls.
Mike
MU-2

Not so, Mike. Spoilers spoil lift. You can't spoil lift that ain't
there
as in a stalled wing.

--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

wrote:
I think the difference in this instance is that ailerons deflect
airflow upward wheras spoilers actually interrupt lift

You don't think deflecting the airflow upward doesn't decrease the
lift?

Darrell S wrote:


Not so, Mike. Spoilers spoil lift. You can't spoil lift that ain't there
as in a stalled wing.


What part of "a stalled wing still generates lift" don't you understand.
A stall occurs at the critical angle of attack. This is the point where
further increase in angle of attack generates no further increase in
lift. The lift goes down, it doesn't disappear.

wrote:
That's a key statement. The definition of stalled, as the FAA and the pilot
see it, is not an aerodynamic definition. It is a definition based on
aircraft
handling and controllability.

Says who?

"Ron Natalie" wrote in message
m...
wrote:
I think the difference in this instance is that ailerons deflect
airflow upward wheras spoilers actually interrupt lift

You don't think deflecting the airflow upward doesn't decrease the
lift?

I think it's fair to say that there's a difference between using the word
"interrupt" and using the word "decrease".

The certification requirements. They do not mention in any way a specific
aoa.
They define stall by how the aircraft acts. Like reaching a stick limit, or
responding in a
direction other than that of a control input. Or, on bigger aircraft, when
the computers
say that the plane is stalled. Back to little planes. The stall varies
widely, mostly
depending on weight and cg position. For example at forward cg, the stall is
often
determined by running out of elevator travel. The airplane isn't really
stalled, but the
certification requirements say it is. Reaching a control limit is a limit.
At aft cg, the
airplane nose may stop rising and may even start dropping with increased
elevator
position. This is a limit, because the aircraft is not responding in the
direction of input.
The same things apply to aileron action. The airplane must respond in the
direction of
control input at conditions above stall speed. Stall characteristics get
into this at the
same time. Even though the aircraft may respond in the proper direction, if
the angle
of bank exceeds a rather small number (15 degrees, as I recall) the stall
characteristics
are deemed unacceptable. Addressing all these problems results in
compromises.

I'm sure that I have not covered the issue well at all. It would be a good
exercise pull
up the certification requirements for light aircraft and read them. After a
month or two
of full time study, a person could come up with a lot of questions on just
how the heck
can you certify any plane.

One other thing. Stall speeds vary considerably with entry rate. The regs
specify a 1
knot per second entry rate. At slower entry rates, the stall speed is
higher. At higher
entry rates, the stall speed is lower. Very, very few instructors do 1 knot
per second
entry rate stalls. It's much more difficult to do than the "bring the nose
up and recover
when it breaks" type. This is my most favorite pet peeve. Many instructors
are avoiding
one of the most insidious parts of the envelope. "There I was, turning final
above stall speed and the plane dove into the ground." Turning flight. Slow
speed
decline. It adds up.


Ron Natalie wrote in message
.. .
wrote:
That's a key statement. The definition of stalled, as the FAA and the
pilot
see it, is not an aerodynamic definition. It is a definition based on
aircraft
handling and controllability.

Says who?