spoilers vs. ailerons

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?

"Ron Natalie" wrote in message
m...
wrote:
OK, but if spoilers "spoil" lift over the wing isn't that an
undesirable condition when low & slow such as a crosswind landing where
the upwind wing is dropped?

What do you think an aileron does in the same situation?

The difference is one of degree, as well as of mechanism.

To address the previous question...

For a given roll rate, a certain amount of force needs to be applied.
Ailerons provide this force in a balanced way, by increasing the angle of
attack on one wing and reducing it on the other. A spoiler, rather than
reducing the angle of attack, simply disrupts the airflow and reducing lift.

So, compared to ailerons, the spoiler is more like using only a single
aileron on the opposite wing to induce the roll (which would put that wing
closer to the stalling angle of attack).

Of course, that all ignores a bunch of other aspects of the situation.
Ailerons, even as they increase the angle of attack, also change the shape
of the wing, which can change the stalling angle of attack. Also, many
ailerons are configured for asymmetric deployment, to help reduce adverse
yaw; the aileron on the down-going wing is deflected more than the aileron
on the up-going wing.

Another element that is actually in favor of spoilers (the previously
mentioned ones are, IMHO, pro-aileron) is that if for some reason deployment
of the spoiler should cause a stall, all that will happen is that the wing
going down will go down faster. The pilot's instinctive response will be
just fine, as reducing or reversing aileron input will simply restow the
spoiler, allowing that wing to generate the required lift again. Contrast
that to slow flight with an aileron, in which not only does the wing stall
induced by aileron input cause a reversal of the rolling moment, but the
pilot's natural reaction would be exactly opposite that required.

Of course, being able to put full-span flaps on a wing also helps compensate
for any potential risk of a stall due to roll control input. It seems
likely to me that, given the situations in which spoilers are often found
for roll control, it's a net gain for the spoilers.

One should not forget that in reality, at typical approach speeds (even
those required for a short-field approach), one ought not to be close enough
to risking a wing stall due to roll control input, whether it's spoilers or
ailerons that are being used. Obviously, spoilers work "well enough" and in
fact in many cases may be a superior solution to ailerons.

Pete

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

"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

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?

I think that the main disadvantage is probably cost and perhaps complexity
or weight, I really don't know. Many jets use spoilers as their primary
roll control. Guys are overthinking this one. If spoilers were really
different then a type rating would be required on a MU-2 and if they were a
problem at low speed they wouldn't be used on a Helio.

Mike
MU-2


"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

Why not just land across the runway.

Why indeed? Just fly off a carrier... those Navy guys never have to
deal with crosswinds when flying off the boat Hmmphh... What's so
darn hard about grabbing a three-wire anyway? : )

Actually with it large vertical stabilizer and relatively small rudder, the
Helio has fairly poor crosswind performance. Most experienced Helio pilots
compensate for this by landing diagonally across the runway

Mike
MU-2


wrote in message
oups.com...
Why not just land across the runway.

Why indeed? Just fly off a carrier... those Navy guys never have to
deal with crosswinds when flying off the boat Hmmphh... What's so
darn hard about grabbing a three-wire anyway? : )

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
--
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