spoilers vs. ailerons

"Matt Whiting" wrote in message ...
Mike Rapoport wrote:

Spoilers function the same as ailerons at low angles of attack and better than ailerons at high angle of attack. The
primary advantage of spoilers instead of ailerons is that it enables full span flaps. Spoilers also reduce or
eliminate adverse yaw.

I assume there must be some disadvantages of spoilers for roll control as you see them so rarely. What are the
drawbacks? Cost??

Matt


What happens when the wing is inverted? If you are pushing negative Gs then the roll control will be reversed?

" Blueskies" wrote in message
m...

"Matt Whiting" wrote in message
...
Mike Rapoport wrote:

Spoilers function the same as ailerons at low angles of attack and
better than ailerons at high angle of attack. The primary advantage of
spoilers instead of ailerons is that it enables full span flaps.
Spoilers also reduce or eliminate adverse yaw.

I assume there must be some disadvantages of spoilers for roll control as
you see them so rarely. What are the drawbacks? Cost??

Matt


What happens when the wing is inverted? If you are pushing negative Gs
then the roll control will be reversed?


It would work the same. The wing doesn't know that it is inverted, all it
knows is AOA.

Mike
MU-2

"Mike Rapoport" wrote in message hlink.net...

" Blueskies" wrote in message m...

"Matt Whiting" wrote in message ...
Mike Rapoport wrote:

Spoilers function the same as ailerons at low angles of attack and better than ailerons at high angle of attack.
The primary advantage of spoilers instead of ailerons is that it enables full span flaps. Spoilers also reduce or
eliminate adverse yaw.

I assume there must be some disadvantages of spoilers for roll control as you see them so rarely. What are the
drawbacks? Cost??

Matt


What happens when the wing is inverted? If you are pushing negative Gs then the roll control will be reversed?


It would work the same. The wing doesn't know that it is inverted, all it knows is AOA.

Mike
MU-2


The wing does know, the AOA is negative. Right side up, the spoiler is deflected and the wing drops. Turn it upside down
and deflect it, the wing still drops.

Just as a comparison, for what it's worth, the B52 doesn't have ailerons but
relies on spoilers for it's roll control.

Shawn
wrote in message
oups.com...
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?

I'm hoping Mike R. will weigh in with his Shmoo experience. IIRC the
MU-2 has the same configuration.

Will

ISTR reading that about the Buff, but with that aircraft the landing
gear is aligned with the runway during an xwind landing and it lands in
a crab. For planes with spoilers and conventional gear I'm curious if
there's a different procedure for xwind landings

Right, but the B52 also has gear that can be aligned with the runway so
it lands in a crab. I'm asking if there's a different method for xwind
landings for conventionally gearly acft with spoilers. Maybe I didn't
phrase the question clearly enough... Mike R whaddya think?

You guys are overthinking this. Aircraft with spoilers have *better* low
speed roll control than those with ailerons.

Mike
MU-2


wrote in message
oups.com...
Right, but the B52 also has gear that can be aligned with the runway so
it lands in a crab. I'm asking if there's a different method for xwind
landings for conventionally gearly acft with spoilers. Maybe I didn't
phrase the question clearly enough... Mike R whaddya think?

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/
-