spoilers vs. ailerons

wrote:
There are two old Senecas at my airport with the Robertson STOL mod -
full span flaps w/spoilers in place of conventional ailerons. I've
seen one of them take off with a brutally short roll, and it went up
as if on an escalator. My question is, how would one of these land in
a stiff x-wind? Is the pilot limited to crabbing approaches with a
kick-out in the flare just above the runway? Or is there no
appreciable difference with ailerons?

Minor differences. The spoiler spoils lift on the side of the raised
spoiler. This normally causes a roll toward the raised spoiler much the
same as aileron movement. Some people always land by trying to get about a
foot above the runway and keep it there by continually raising the nose as
speed decreases. If you actually stall the wings it only drops a foot.
That's with an aileron aircraft. 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. So if you were cross-controlling a wing
low for crosswind you'd lose the roll control but still have the rudder
input. A perfect example of that is the B-52H that crashed in Spokane, WA,
maneuvering at low altitude for a fly-by the airport. He got it into
almost 90° of bank and stalled the wings. Pictures taken just prior to the
crash show the upper wings spoilers fully extended as he rolled the control
column to try to roll out of the bank. Useless attempt. If the wing lift
is already gone the spoiler now does nothing to control the roll. If he'd
quickly pushed top rudder he might have been able to yaw the aircraft
towards wing level, reducing G force and making the wing fly again.

As long as the spoiler is at or close to the center of lift, deploying a
spoiler will not also cause a pitching tendency. If it is aft of the center
of lift (as in the B-52H) it also produces a pitch up. During airport
traffic flying we usually moved the airbrakes to position 4 (if I remember
40 years ago right). This way rolling the wheel caused the downward moving
wing spoiler to move up more and the upward moving wing spoiler to move down
some. This eliminated the pitch up/down while manuevering. The extra drag
required more power, putting the throttles into a more responsive range. It
also caused the speed to bleed off more rapidly when retarding the thottles
for landing.

--

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

"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

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/
-

"Darrell S" wrote in 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.

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

That seemed to be quite a topic not too long ago re spins.

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism

Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Blog: http://www.skywise711.com/Blog

Sed quis custodiet ipsos Custodes?

"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

"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

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/
-

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:
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?