spoilers vs. ailerons

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

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.

Mike
MU-2




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

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? Does that make airspeed control even more
critical, or is that not a consideration? Is a x-wind landing done the
same way?

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?

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

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/
-

wrote in news:1122393811.505648.264850
@g49g2000cwa.googlegroups.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


Why not just land across the runway.

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

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

IIRC in this case an up aileron deflects airflow upward wheras a
spoiler interrupts or "spoils" the lift of the wing. I'm curious if
that represents an unsafe situation when down low