why p61 spoilerons?
dumbstruck
ailerons, but why a fighter like the p61? Do spoilerons even work if
your apparent gravity is to the side or upside down?
Spoilerons are cool because they don't yaw you in the wrong direction
- the inboard wing gets drag rather than the outboard. But since they
work by killing lift, don't they operate properly only when relatively
horizontal (yeah I realize a barrel roll is ok due to apparent gravity
direction changing)?
So what if turbulance tosses you on a 90 degree or more roll in a p61,
b52, or some sailplanes... do you still have roll authority to
recover? I think boeing airliners may have the best approach of having
both ailerons and small spoilerons.
tscottme
news:e1a189ab-36eb-4e09...@x25g2000prf.googlegroups.com...
The wing doesn't remember where the earth was it only reacts to the
aerodynamic forces. Spoilerons react just as well upside down as right side
up. I think the usual knock on spoiler roll control is that in low airspeed
or near-stall conditions. But training helps there.
--
Scott
Liberals are America's Death Panel.
"A liberal is a person who sees a fourteen-year-old girl performing live sex
acts onstage and wonders if she's being paid the minimum wage."
-- Irving Kristol
vaughn
"dumbstruck" <dumb...@gmail.com> wrote in message
news:e1a189ab-36eb-4e09...@x25g2000prf.googlegroups.com...
> b52, or some sailplanes... do you still have roll authority to
> recover? I think boeing airliners may have the best approach of having
> both ailerons and small spoilerons.
AFAIK: no flight controls need gravity to work. As long as the spoilers (or
ailerons) somehow develop asymmetric lift, it should make no (or little)
difference if the plane is in level flight, they will produce a rolling
force.
Many sailplanes have spoilers for glidepath control, but I don't know of any
that use them for roll control. (the spoilers open & close together)
One plane that I know for a fact uses spoilers exclusively for roll control
is the Mitsubishi MU-2. This plane once had an accident rate that was bad
enough to have it singled out by the FAA for special action. After some
special training was required fleetwide, the problem seems to have
diminished. Here is a document that covers "myths" about the MU-2's spoiler
roll control. http://mu-2aircraft.com/upload/files/mu-2_myths.pdf
Vaughn
dumbstruck
wrote:
> AFAIK: no flight controls need gravity to work. As long as the spoilers (or
> ailerons) somehow develop asymmetric lift, it should make no (or little)
> difference if the plane is in level flight, they will produce a rolling
> force.
Weird, what is really happening is the spoileron is NEUTRALIZING the
aerodynamic force of the wing to be depressed, and by default the lift
of the other wing will roll you around. So you aren't directly
applying or using any conventional control force, but tweaking the
existing lift forces to exert control. I should have realized this is
independent of gravity, but it's quite a brain teaser.
It's somewhat similar to having one aileron broken, and only the
upward hinging one working (to kill the lift). I remember a web page
discussing a hybrid where the downward aileron movement is geared move
less than the upward movement - I think I like that approach (I hate
fussing with turn coordination).
> Many sailplanes have spoilers for glidepath control, but I don't know of any
> that use them for roll control. (the spoilers open & close together)
J4 Javelin spoilerons are promoted for no adverse yaw
http://www.sailplanedirectory.com/PlaneDetails.cfm?planeID=174
> One plane that I know for a fact uses spoilers exclusively for roll control
> is the Mitsubishi MU-2. This plane once had an accident rate that was bad
> enough to have it singled out by the FAA for special action. After some
> special training was required fleetwide, the problem seems to have
Oh, that's too bad. It sounds similar to http://en.wikipedia.org/wiki/P-61_Black_Widow#Design
where they wanted the trailing edge to all be taken up by flaps
(although I don't know why P61 needed flaps so bad). The midchord
spoilerons work fine and any slight efficiency loss is made up for by
saving rudder drag. But some arcane emergency procedures are
profoundly different with spoilerons, and your aileron muscle memory
or whatever can work against you.
vaughn
>I remember a web page
>discussing a hybrid where the downward aileron movement is geared move
>less than the upward movement
Actually that is pretty common. It is one way that designers breed the
adverse yaw out of airplanes.
>(I hate fussing with turn coordination).
Then you would hate sailplanes. Seriously; once you learn that little dance
step on the rudder pedals, it happens automatically.
> It sounds similar to http://en.wikipedia.org/wiki/P-61_Black_Widow#Design
>where they wanted the trailing edge to all be taken up by flaps
>(although I don't know why P61 needed flaps so bad).
I think that was also the strategy on the MU-2. Those full-span flaps allow
high wing loading and almost jet-like speed without sacrificing low speed
performance. That is why the call the MU-2 the "rice rocket". Replacing
the ailerons with spoilers makes room for the flaps. (I am no aero engineer
and don't play one on the Internet)
Vaughn
kirk....@gmail.com
> J4 Javelin spoilerons are promoted for no adverse yawhttp://www.sailplanedirectory.com/PlaneDetails.cfm?planeID=174
I did a test flight in an early J4 at the old Vacaville gliderport
back in about 1978 - very odd flying glider, weak roll control and
poor glidepath control. The day after I flew it some poor schmuck
killed himself in it, apparently trying a low 360 on final - perhaps
caused by the poor spoiler effectiveness? Lack of adverse yaw didn't
help him much. There is a good reason spoilers are not used for roll
control in gliders - they are all drag, which is what serious glider
pilots and designers avoid as much as possible!
OTOH, I've got a lot of time in the good old F-4, which used spoilers
and ailerons together. It rolled quite nicely, thankyou (but the
hardwing models still had enough adverse yaw to put you in a spin if
the ailerons were used at high AOA...).
Kirk
66
dumbstruck
wrote:
> > J4 Javelin spoilerons are promoted for no adverse yawhttp://www.sailplanedirectory.com/PlaneDetails.cfm?planeID=174
>
> I did a test flight in an early J4 at the old Vacaville gliderport
> back in about 1978 - very odd flying glider, weak roll control and
> poor glidepath control. The day after I flew it some poor schmuck
> killed himself in it, apparently trying a low 360 on final - perhaps
> caused by the poor spoiler effectiveness? Lack of adverse yaw didn't
> help him much. There is a good reason spoilers are not used for roll
> control in gliders - they are all drag, which is what serious glider
> pilots and designers avoid as much as possible!
Here is a test report that confirms your J4 findings.
http://www.scalesoaring.co.uk/VINTAGE/Documentation/Javelin/J-4_JavelinArticle.pdf
But the Mu-2 pdf given earlier claims the spoilers save as much drag
as they create (by cutting rudder deflection).
I've got to think spoilerons act weird at large negative angles of
attack. Whether you are upside down or doing at least part of an
outside loop, they are going to end up on the wrong side of the wing.
That turns them into a flaperon. Apparently the v22 uses those ok, but
the p61 midchord position of an upside down spoileron seems all wrong
for that purpose. Maybe nightfighters aren't expected to pull minus g.
Steve Hix
<37500003-d27e-4a2f...@j9g2000prh.googlegroups.com>,
dumbstruck <dumb...@gmail.com> wrote:
> On Oct 1, 10:39�am, "vaughn" <vaughnsimonHATESS...@gmail.FAKE.com>
> wrote:
> > AFAIK: no flight controls need gravity to work. �As long as the spoilers (or
> > ailerons) somehow develop asymmetric lift, it should make no (or little)
> > difference if the plane is in level flight, they will produce a rolling
> > force.
>
> Weird, what is really happening is the spoileron is NEUTRALIZING the
> aerodynamic force of the wing to be depressed, and by default the lift
> of the other wing will roll you around. So you aren't directly
> applying or using any conventional control force, but tweaking the
> existing lift forces to exert control.
Ailerons do the same thing, in the other direction. Aileron goes down,
changing the camber of its part of the wing, increasing lift (to raise
that wing) and drag (resulting in adverse yaw). The aileron on the other
side reduces lift on that wing, and is often rigged to move up more than
the other moves down to generate a bit more drag to reduce adverse yaw a
bit.
WaltBJ
approach speed, better for making a weather approach when the ducks
are walking. Spoilers might have been a simpler approach to lateral
control than arranging ailerons to drop with flaps like some other
aircraft.
Walt BJ
vaughn
>Whether you are upside down or doing at least part of an
>outside loop, they are going to end up on the wrong side of the wing.
>That turns them into a flaperon.
You seem to have regressed.
I thought we told you that the wing does not know where it is in reference
to the earth. It is just an airfoil acting in a huge river of air. On the
other hand, your earlier comment about angle of attack (AOA) affecting them
may well be correct, but that might also be true for ailerons. As always,
the devil is in the details. That is why we have engineers.
Vaughn
Ed Rasimus
Not yet mentioned here, but the F-105 had a hybrid system for roll
control. Eight spoilers on top of each wing along with conventional
ailerons. At high indicated air speed the ailerons locked out and roll
was exclusively by spoilers.
It was a response to the serious adverse yaw problem of the F-100 and
was very effective. You could fly the airplane quite nicely with feet
flat on the floor--but you could fly it much better with applications
of rudder where appropriate. No adverse yaw though.
After 1967 the aircraft were modified with an emergency system for
total hydraulic loss. With a flip of the switch all hydraulic control
surfaces were locked in neutral. Slab was set to approx 350 KIAS.
Pitch control was done with throttle--increase to climb, pull back to
descend and aircraft would seek 350. Roll was done with differential
flaps since they were electrically actuated not hydraulic. A small
toggle switch controlled the flap movement.
The system was purely for sufficient control to get out of enemy
territory, not to land the aircraft.
Ed Rasimus
Fighter Pilot (USAF-Ret)
www.thundertales.blogspot.com
www.thunderchief.org
guy
> "dumbstruck" <dumbst...@gmail.com> wrote in message
I suspect dumbstruck means an aeroplane flying straight and level,
inverted, where the lift generated is in the opposite direction to
normal relative to the airframe.
Guy
dumbstruck
wrote:
> >Whether you are upside down or doing at least part of an
> >outside loop, they are going to end up on the wrong side of the wing.
> >That turns them into a flaperon.
>
> You seem to have regressed.
>
> I thought we told you that the wing does not know where it is in reference
> to the earth. It is just an airfoil acting in a huge river of air. On the
> other hand, your earlier comment about angle of attack (AOA) affecting them
> may well be correct, but that might also be true for ailerons. As always,
> the devil is in the details. That is why we have engineers.
Upside down or an outside loop means high negative angle of attack
because the wings are lifting in the opposite direction. In fact it
can be just part of an outside loop which leaves you upright - think
of a noseover or vomit comet path.
Spoilerons are not equivilent to ailerons, or else they would have
equal adverse yaw. I've got to think they would transform into the
world's worst flaperon when upside down. Maybe the P61 couldn't fly
extended upside down anyway, or B52. But I hope any spoileron equipped
century fighters still flying will take heed, and put a warning label
in the cockpit that high negative G's are not recommended by
dumbstruck!
More seriously, there used to be a fantastic web version of an
aircraft control textbook with flash animations and all. It has
disappeared or changed it's URL. So if anyone can find it again, it
makes great ammunition for newsgroup debate (I think it was from a
Canadian university).
Ed Rasimus
<dumb...@gmail.com> wrote:
>On Oct 2, 2:20�am, "vaughn" <vaughnsimonHATESS...@gmail.FAKE.com>
>wrote:
>> >Whether you are upside down or doing at least part of an
>> >outside loop, they are going to end up on the wrong side of the wing.
>> >That turns them into a flaperon.
>>
>> You seem to have regressed.
>>
>> I thought we told you that the wing does not know where it is in reference
>> to the earth. �It is just an airfoil acting in a huge river of air. �On the
>> other hand, your earlier comment about angle of attack (AOA) affecting them
>> may well be correct, but that might also be true for ailerons. �As always,
>> the devil is in the details. �That is why we have engineers.
>
>Upside down or an outside loop means high negative angle of attack
>because the wings are lifting in the opposite direction. In fact it
>can be just part of an outside loop which leaves you upright - think
>of a noseover or vomit comet path.
>
>Spoilerons are not equivilent to ailerons, or else they would have
>equal adverse yaw. I've got to think they would transform into the
>world's worst flaperon when upside down. Maybe the P61 couldn't fly
>extended upside down anyway, or B52. But I hope any spoileron equipped
>century fighters still flying will take heed, and put a warning label
>in the cockpit that high negative G's are not recommended by
>dumbstruck!
We are concerned with management of parasite drag not induced which
is a by-product of creating lift. Parasite drag is form drag--barn
doors have high parasite drag. Induced drag is created by high angle
of attack and turbulence in the airflow. Stall, by definition is the
angle of attack at which a further increase of AOA will generate more
drag than lift.
Ailerons create a greater parasite drag on the down side than the
raised side--hence adverse yaw, a drag on the side away from the
direction of intended turn. Whether the wing is generating lift or
not, you still have parasite drag when you deflect an aileron set,
more on the down deflection than the up, hence yaw the wrong way.
"Inverted flight" doesn't mean lift generation by an upside down wing
necessarily. You are only inverted with respect to the earth, not to
the "relative wind" or airflow over the wing. To truly generate lift
with an inverted wing you need one with a camber on both top and
bottom, i.e. a symmetrical airfoil, or you need a completely different
angle of attack situation. Aircraft, other than those designed for
inverted flight, generally don't have extended inverted flight
capability because of issues with fluids and pressures--hydraulics,
fuel, lubricant, etc.
Spoilers are disruptors of airflow on the top or cambered surface of
the wing. There is no "downward deflected side", hence no adverse yaw.
The are disrupting lift creation and only minimally creating parasite
drag.
A wing has no "upside down" and inverted flight has no tactical
applications. Being inverted relative to the earth is not the same as
level inverted flight (flight at minus 1G). No warning labels in the
cockpits are needed, even from dumbstruck.
euno...@yahoo.com.au
> I can guess why a b52 might control roll by spoilerons rather than by
> ailerons, but why a fighter like the p61? Do spoilerons even work if
> your apparent gravity is to the side or upside down?
Spoilerons were used in the B-52 because they do not induce a twisting
moment in the wing, which is a problem in any aircraft but more so a
large span swept wing aircraft such as the B-52 where it is difficult
to maintain torsional rigidity. Ailerons with a lack of wing
torsional rigidity can lead to 'aileron reversal' where the aileron
acts as a servo tab and twists the wing to such an extent that the
aircraft rolls in the opposite direction. The WW2 spitfire was
notably effected by this due to its thin wing and it had a relatively
low 'reversal speed' (Improved in the 20 series)
Early B-52 used a pair of small feeler ailerons connected to the
pilots yokes to provide feel and some manual backup while 6
hydraulically operated spoilers provided role control. B-47 also used
this solution I believe. Many aircraft switch of their outer ailerons
(B707) at high speed.
Spoilers have a bit of a reputation for allowing for post stall roll
control.
In addition they do not cause adverse yaw. In a normal aileroned
aircraft the downward deflected aileron that is producing 'lift' will
produce more drag than the equally upward deflected aileron and this
would cause the aircraft to turn against the direction of the bank
(and likely turn) Solutions include differential ailerons (Me 109)
whereby mechanical set up cause the upward deflection to be greater
than the downward deflection or Friese ailerons (P-47, Fw 190) whereby
a portion of the aileron juts into the lower airstream to increase
drag and relieve control force. Automatic deflection of the rudder is
another used in modern controls.
Spoilers also double for speed brakes and lift dumpers to allow
steeper descents in aircraft that are too slippery such as sailplanes
and some jets.
Me 109T1 (for aircraft carrier) was to have spoilers.
>
> Spoilerons are cool because they don't yaw you in the wrong direction
> - the inboard wing gets drag rather than the outboard. But since they
> work by killing lift, don't they operate properly only when relatively
> horizontal (yeah I realize a barrel roll is ok due to apparent gravity
> direction changing)?
If you are flying sideways you are using the aircraft fueselage as a
wing, if you are flying upside down you are probably in an aircraft
with symmetrical wings such as a fighters or acrobatic aircraft. The
spoilers will still roll in the correct direction as they don't work
by providing loss of lift but by providing negative lift (when
upright).
This is why a split flaps works as well.
The drag increase is not that great at least for modest deflections.
Paul J. Adam
<rasimus...@verizon.net> writes
>Not yet mentioned here, but the F-105 had a hybrid system for roll
>control. Eight spoilers on top of each wing along with conventional
>ailerons. At high indicated air speed the ailerons locked out and roll
>was exclusively by spoilers.
>
>It was a response to the serious adverse yaw problem of the F-100 and
>was very effective. You could fly the airplane quite nicely with feet
>flat on the floor--but you could fly it much better with applications
>of rudder where appropriate. No adverse yaw though.
>
>After 1967 the aircraft were modified with an emergency system for
>total hydraulic loss. With a flip of the switch all hydraulic control
>surfaces were locked in neutral. Slab was set to approx 350 KIAS.
>Pitch control was done with throttle--increase to climb, pull back to
>descend and aircraft would seek 350. Roll was done with differential
>flaps since they were electrically actuated not hydraulic. A small
>toggle switch controlled the flap movement.
>
>The system was purely for sufficient control to get out of enemy
>territory, not to land the aircraft.
And threads like this, with high-grade content from multiple experienced
contributors, is why r.a.m is still worth reading.
--
He thinks too much, such men are dangerous.
Paul J. Adam
coffelt2
<euno...@yahoo.com.au> wrote in message
news:23b3ab18-f418-4f4d...@u36g2000prn.googlegroups.com...
About the B-47's spoilers: OK, it's been nearly 50 years since I
regularly rigged it's
flight controls, but when the yoke was turned, several events occurred in
sequence, some
depending on if hydraulic power was available (or not), and whether the
flaps were down
(or not).
First rotation of yoke wheel moved aileron hydraulic actuator pilot
valve which caused
hydraulic power to move aileron. BUT, if hydraulic power was not available,
a bit of yoke
over travel (something like 3 degrees?) caused physical, cable operated
mechanical aileron movement.
NOW, if hydraulic power WAS available, when the aileron traveled "UP" a
few degrees
(five or six?? 50 years ago), the spoiler hydraulic actuator pilot valve
caused that wing's spoiler to begin opening
as well.
ADDITIONALLY, if the gear and flaps were down, one of the two flap
sections on the wing with upward
aileron movement would "dump". Thus giving considerably increased roll
authority in slow speed flight.
Not absolutely sure, but I think it was the outboard flap section on each
wing which was called the
"flaperon" as it functioned both as flap and aileron (at low airspeed with
gear extended).
Old Chief Lynn
euno...@yahoo.com.au
> <eunome...@yahoo.com.au> wrote in message
>
> news:23b3ab18-f418-4f4d...@u36g2000prn.googlegroups.com...
> On Oct 2, 6:48 am, dumbstruck <dumbst...@gmail.com> wrote:
>
Thankyou so much for that explanation. I had often wondered how an
aircraft transitioned from full powered hydraulics to manual
reversion. This preseumably means the pilot had a 'deadband' of 3
degrees of so for aileron travel if he lost hydraulic power.
In power boosted controls I immagine loss of hydraulic pressure
probaly leads to a spring loaded pin connecting up the control cables
directly to get rid of the 'dead zone' you mention.
coffelt2
<euno...@yahoo.com.au> wrote in message
news:f2a6d80d-53ec-42b0...@f18g2000prf.googlegroups.com...
Well, the transition from power to manual aileron movement was somewhat
like this:
The main, yoke wheel to aileron cables went directly to a quadrant
which would
manually move the aileron itself. This quadrant was designed to have that
three
or four degrees of "slop". That "slop" allowed the hydraulic pilot valve,
linked to the
quadrant to move the aileron under power, before the "slop" was used up.
Now, there WAS a spring loaded valve built into the hydraulic actuator
(a "power
pack" it was called). This valve was closed by hydraulic pressure if
hydraulic system
was functioning normally. However if power failed, this spring loaded valve
would
pop open and allow a fluid by-pass from the opposite ends of the hydraulic
actuating
cylinder. Otherwise, there would be a hydraulic "lock", preventing manual
override.
It is a fairly simple system, which proves harder to describe in words
than
it should.
Old Chief Lynn
under power
Peter Stickney
Chief,
I hate to contradict a guy who has Been There and Done that, but I've
never seen a B-47 with spoilers. Every one I've seen (Including the last
official flight on a -47 - the delivery of a Navy B-47E (Used as a Tu-16
simulator for OPFOR work in the '70s) to Pease AFB as a gate guard in '78.
was ailerons only, with, as you say, the outboard flap sections serving as
flaperons when everything was hanging out.
Be that as it may, the B-47 taught Boeing and pretty much everybody else a
lot about wing flexibility and reversal speeds. At a bit over the limit
speed of 425 KEAS, the aileron flexing the wing would make the airplane
roll in the opposite direction to the control input. This was a serious
issue when the B-47 started moving to low level penetration profiles.
(The B-52, despite being bigger and more flexible is limited to 400 KEAS.)
Great to see that you're still around - sorry for the contradiction.
--
Pete Stickney
The better the Four Wheel Drive, the further out you get stuck.
coffelt2
"Peter Stickney" <p_sti...@verizon.net> wrote in message
news:v1qrq6-...@Aerie.local.net...
> Chief,
> I hate to contradict a guy who has Been There and Done that, but I've
> never seen a B-47 with spoilers. Every one I've seen (Including the last
> official flight on a -47 - the delivery of a Navy B-47E (Used as a Tu-16
> simulator for OPFOR work in the '70s) to Pease AFB as a gate guard in '78.
> was ailerons only, with, as you say, the outboard flap sections serving
> as
> flaperons when everything was hanging out.
>
> Be that as it may, the B-47 taught Boeing and pretty much everybody else a
> lot about wing flexibility and reversal speeds. At a bit over the limit
> speed of 425 KEAS, the aileron flexing the wing would make the airplane
> roll in the opposite direction to the control input. This was a serious
> issue when the B-47 started moving to low level penetration profiles.
> (The B-52, despite being bigger and more flexible is limited to 400 KEAS.)
>
> Great to see that you're still around - sorry for the contradiction.
> --
> Pete Stickney
Pete,
We had a great time rigging and rerigging our B-47Es for LABS
maneuvers. (the low level penetration you mention)
Each ship had to be individually rigged to require less than quite a
few
degrees of aileron trim and less than so many inch-pounds of control wheel
torque to maintain level flight at somewhat over the
425 Knots you cite. I wish I could remember the exact number of
degrees and the exact airspeed to meet the trim requirements, but it
was a tight fit, I'll say. I think only one ship in our Wing could not be
made to meet those new requirements.
After a day or two shooting an alignment of the ship that, we
found the right wing had a twist exceeding the -3 limits. Further
investigation in records revealed that that wing was out of limits when
it was delivered by Boeing new. The discrepancy was noted in the records
and was signed off and inspected by the Air Force officer accepting the
aircraft. I have forgotten just what they called that officer now, but
apparently he could accept minor discrepancies in new aircraft.
I first noted the spoiler panels, near the aileron power packs, when
my boss, T/Sgt Sjoquist said, don't put your tool bag there, or sit there
when the ailerons are operated, you or the tool bag might get boosted
right off the wing! He was so right! As I recall, they were pretty much a
"bang-bang" deployment, up or down, without much in between, and maybe
they operated only under the same conditions that flaperons dumped?
Old Chief Lynn
Eunometic
> "Peter Stickney" <p_stick...@verizon.net> wrote in message
>
> news:v1qrq6-...@Aerie.local.net...
>
>
>
>
>
> > Chief,
> > I hate to contradict a guy who has Been There and Done that, but I've
> > never seen a B-47 with spoilers.
> I first noted the spoiler panels, near the aileron power packs, when
> my boss, T/Sgt Sjoquist said, don't put your tool bag there, or sit there
> when the ailerons are operated, you or the tool bag might get boosted
> right off the wing! He was so right! As I recall, they were pretty much a
> "bang-bang" deployment, up or down, without much in between, and maybe
> they operated only under the same conditions that flaperons dumped?
Just googling at bit comes up the with the fact that Boeing used
spoilers on the B-47 prototypes because of a concern that wing
twisting would degrade roll controll to much but that this was
considered unnnecesary for production aircraft. Later at least one
other
B-47 were later used for spoiler experiments. So, its certainly
possible that given the aircraft had spoilers that they could be
rigged to also provide roll control.
dumbstruck
pilots talked about their most scary experiences on a CSPAN3 panel
this weekend. Actually I think this occurred in the follow-on SR-71,
but they considered that a downgrade and didn't like to mention that
slower 2 place model. It was part of the area51 lecture series held at
http://www.atomictestingmuseum.org/
One pilot is cruising at mach 3.25 and focused on the instruments
since this is the cusp of the point where compressor blades are
wrecked by the heat (that is typically the speed limiter, and thus can
vary by outside air temp). He notices shadows over the instrument
panel moving, yet the instruments indicate steady flight. Looking out,
he notices he is 90 degree rolled! At this speed he has to very, very
gingerly roll back to horizontal, throttle back, and nose up -
apparently power was lost to the instrument panel and gauges stuck
where they were.
How the heck can spoilerons work if you are accidentally set sideways
in a storm cloud or whatever? I mean where you have no apparent
positive G's in the seat or positive angle of attack. It only works
from the principle of milking existing positive G (from the opposite
wing) to induce roll, so should have almost no effect in recovering
from 90 degrees or even rolling a level aircraft doing a vomit comet
arc... when both invoke zero G. It may have a slightly useful effect
when an aircraft is steady state upside down, but on-edge it's only
effect would seem to be a touch of yaw from parasitic drag. Regardless
of induced vs parasitic drag, an aileron will act like a fin and be
effective regardless of apparent gravity.
P.S. on the A-12 pilots... a more scary story was (possibly in their
less favored SR-71 steed this time too) was being SAMed over Hanoi.
Due to refueling over Thailand, they didn't have enough running room
to get up to max speed over target areas, so this guy found at least 4
SAMs first shot up over him, then ran horizontally to make a classic
explosion just off his tailpipe. He could tell from his rear periscope
that once the contrails turned to explosions, the puff would recede at
incredible speed. He decided these were fair "hits" but he was
outrunning the flak! At debriefing, he wasn't believed until some
ground crew came running in with news they found a tiny piece of SAM
embedded in the bird. I assume SAM flak has awful ballistic
coefficients (I hear even 20mm cannons can't reach far in high speed
combat).
Ed Rasimus
Once again I will try to point out that the wing doesn't know whether
it is upright, inverted or at knife-edge to the horizon. It doesn't
care. It only requires airflow to be over the surfaces. That can be
straight up or straight down (how does your 90 degree bank example
work if the pure vertical? What is 90 degrees of bank if you are
measuring relative to the horizon which is the same number of degrees
off your nose in all directions?)
The wing doesn't care about g-load either. The best way to recover
airspeed is to go to maximum power and zero-g. That means you are
producing no lift with the wing airfoil and therefore with no lift
produced you also produce no induced drag! You still have parasite
drag or form drag, but no induced drag--result is best acceleration.
If you do it in a descent, you also can add some acceleration due to
gravity.
But roll controls remain at zero g. I could easily do aileron rolls at
very high rates in the T-38 with zero g. I could easily roll to keep
an adversary in sight, maintain visual on a target, or orient myself
for the next maneuver in any fighter I ever flew.
As for SR-71s over Hanoi, that story never happened. It might have
been over other places in the world, but not Hanoi, since the only SAM
beyond MANPADs was the SA-2 and it didn't reach as high as SR-71
profiles nor did it have the speed to tail chase an SR. No problem
with U-2 as Gary Powers discovered, but no threat at all to SR.
SAM "flak" is an oxymoron. And, 20mm cannons don't know how fast their
launch platform is traveling. If muzzle velocity is 3500 fps at zero
airspeed, it is at Mach 2 as well. Once clear of the muzzle, there are
other factors involved, but there is more range extension by high
speed than range loss. Net overall is minimal and not a factor for
aircrew consideration.
Steve Hix
<e17ca048-078f-4ef5...@b3g2000pre.googlegroups.com>,
dumbstruck <dumb...@gmail.com> wrote:
> How the heck can spoilerons work if you are accidentally set sideways
> in a storm cloud or whatever?
If you reduce the lift produced on one wing (which is what activating
spoilers does), since the other wing is still producing lift as before,
you have an asymmetric lift distribution across the span. You will roll
toward the side being acted on by the spoiler.
> I mean where you have no apparent
> positive G's in the seat or positive angle of attack.
The wings don't much care what your seat is feeling, just what it sees
as the air flows over it.
> It only works from the principle of milking existing positive G (from the opposite
> wing) to induce roll,
That's called "lift". Wings produce it. If one makes more than its mate
on the other side, rolling toward the wing producing the most lift is
the usual result.
Any "positive G" is only a result of accelerations produced one way or
other by lift/thrust/drag.
dumbstruck
I think my wording is being misinterpreted. I'll try once more to
remove ambiguity to reveal the rightness of my claims. Well, there may
be one hole in my argument that allows spoilerons to not completely
fail, but it is obscure enough to leave for the end.
> Once again I will try to point out that the wing doesn't know whether
> it is upright, inverted or at knife-edge to the horizon. It doesn't
> care. It only requires airflow to be over the surfaces. That can be
> straight up or straight down (how does your 90 degree bank example
> work if the pure vertical? What is 90 degrees of bank if you are
> measuring relative to the horizon which is the same number of degrees
> off your nose in all directions?)
That pure vertical flight is a great way of visualizing it. But not a
vertical ATTITUDE... it must be a vertical PATH ( and assume zero
wind). I could imagine a spoileron working with vertical ATTITIDE
because the wings (one of them anyway) still has lift from positive
angle of attack of airflow vs the wing. But a vertical PATH implies a
zero angle of attack, and when you apply the spoileron you won't have
the lift of that opposite wing to roll you around. What force a
spoileron does apply to the zero AOA wing must be just a little yaw,
while I assume both wings would remain about zero lift.
My knife edge visual has some advantage if you consider it like a
Thunderbird scooting low over a runway. He isn't just keeping his
attitude along the runway, but PATH. So that enforces no net
aerodynamic forces to one or the other side of the runway. Therefore I
don't see how a spoiler could help him roll back upright except for
stray side effects of it. This is putting aside what he does to keep
the nose fighting gravity via rudder action.
> The wing doesn't care about g-load either. The best way to recover
> airspeed is to go to maximum power and zero-g. That means you are
> producing no lift with the wing airfoil and therefore with no lift
> produced you also produce no induced drag! You still have parasite
> drag or form drag, but no induced drag--result is best acceleration.
> If you do it in a descent, you also can add some acceleration due to
> gravity.
>
> But roll controls remain at zero g. I could easily do aileron rolls at
> very high rates in the T-38 with zero g. I could easily roll to keep
> an adversary in sight, maintain visual on a target, or orient myself
> for the next maneuver in any fighter I ever flew.
I thought T-38 had no spoilerons, and even century fighters only had
them as supplementary to ailerons!? Sure, ailerons can work regardless
of attitude since they can work like rocket or fish fins giving
negative or positive lift. Now it does seem odd that a B-52 would have
virtually no roll control in zero G under my theory, as well as any of
your century fighters in pure spoileron mode, if any. (again, zero G
or vertical flight is an imperfect way of expressing the net-zero-wing-
lift situation that I try to construct with the Thunderbird example).
There is only one reason I can see to not have Obama ground the B-52
fleet right now (besides to avoid the Norwegian Nobel trap).
Spoilerons probably are artificially boosted in effectiveness by the
fact main wings normally have excess lift that is balanced out by
negative lift in the tail. So you may have no NET lift available to
either side of the plane that could potentially exert roll moment, but
the spoileron is attached to a wing that still has a bit of lift to
cancel out the negative lift of the tailplane. Therefore I only call
on Brits to ground the delta Vulcan bomber, which I actually saw
thunder by a few months ago!
> As for SR-71s over Hanoi, that story never happened. It might have
> been over other places in the world, but not Hanoi, since the only SAM
> beyond MANPADs was the SA-2 and it didn't reach as high as SR-71
> profiles nor did it have the speed to tail chase an SR. No problem
> with U-2 as Gary Powers discovered, but no threat at all to SR.
Actually he said North Viet Nam, which with trepididation I shortened
to Hanoi since it was way off the point and thought likely. Like I
said he hadn't been able to get up to speed yet; I've lost track of
the online pilots manual, but they talked about taking half the USA
just to slow it down and maybe a lot more than Thailand was needed to
speed up. He said all the SAMs went to 95,000 which was above him,
then angled down and chased him horizontally. Judging from him
apparently personally tracking the missles (by sensor, then by eye), I
would guess this was on the A-12 rather than SR-71.
> SAM "flak" is an oxymoron. And, 20mm cannons don't know how fast their
> launch platform is traveling. If muzzle velocity is 3500 fps at zero
> airspeed, it is at Mach 2 as well. Once clear of the muzzle, there are
> other factors involved, but there is more range extension by high
> speed than range loss. Net overall is minimal and not a factor for
> aircrew consideration.
Flak is the term he used, obviously casually for the shotgun like
blast of fragments. In particular he referred to a piece of SAM fuse
which had identifiable Soviet style threads on it. He displays it in a
clear resin block embedded in the piece of titanium they cut out of
the aircraft. I believe he said it was like a little fingernail shape,
which sounds plausible for much of the debris and would likely have
horrible ballistic coefficients. I thought this point was made for
even well shaped projectiles, such as 20mm shooters having to take
care not to run into their own deaccelerating bullets after dipping
into a dive.
The A-12 stories may contain some fluff, although they are off the
point anyway. But for full disclosure the talkers were surprisingly
elderly (one non-A12 pilot seemed on the cusp of dementia). The
memories could be a bit skewed - they did have a handbag fight about
why the A-12 really got cancelled. By the way, a younger panel member
claimed as of 4 years ago he visited a huge hanger of SR-71 spare
parts made to last for decades after the tool dies were destroyed. It
was slated to be shut down, but sounded like you could build a large
fleet of the things because they saved every nut and bolt.
dumbstruck
> If you reduce the lift produced on one wing (which is what activating
> spoilers does), since the other wing is still producing lift as before,
> you have an asymmetric lift distribution across the span. You will roll
> toward the side being acted on by the spoiler.
>
> > I mean where you have no apparent
> > positive G's in the seat or positive angle of attack.
>
> The wings don't much care what your seat is feeling, just what it sees
> as the air flows over it.
The whole point is the ZERO LIFT scenario. Zero angle of attack, or
whatever it takes. No lift to roll the non spoilered wing around. That
is what the knife edge or zero G talk is aiming at, although any
attempt at brevity gets it taken the wrong way.
Ailerons differ from spoilerons in that they can create negative lift,
at least by themselves if not overcoming all the wing's lift. All a
spoileron can do is switch off Bernouli principle lift, not reverse it
(as far as I know). The only way spoilerons work when both wings have
zero lift (1&2 somewhat weak):
1) assume a spoileron can create negative lift (a little neg lift is
plausible, but never claimed here and not proven)
2) there are more than 2 lifting wings, and they cancel out except
when a spoileron is accutated (like typical negative AOA tailplane
scenario)
3)?
P.S. I meant to issue the previous grounding for only spoileron
equipped Vulcans, which probably don't exist. If there are no valid
arguments with my theory on the dangers of spoilerons, I have a modest
proposal. To be a good sport about past conflicts, I propose all
spoileron-flying war veterans be subject to a Roman military style
decimation. Not to be killed, but 1 out of 10 to be returned to enemy
POW camps, since their spoilerons only worked due to luck rather than
robust design. This won't be too bad for those bound for Hanoi hilton
or Japan and German equivilant since they may be 5 star resort spas by
now, but I don't envy those bound for North Korea.
Steve Hix
Steve Hix <se...@NOSPAMmac.comINVALID> wrote:
Dang. "...rolling *away* from the wing producing more lift..."
Steve Hix
<69269b98-5009-45aa...@i12g2000prg.googlegroups.com>,
dumbstruck <dumb...@gmail.com> wrote:
> On Oct 19, 1:42�pm, Steve Hix <se...@NOSPAMmac.comINVALID> wrote:
> > If you reduce the lift produced on one wing (which is what activating
> > spoilers does), since the other wing is still producing lift as before,
> > you have an asymmetric lift distribution across the span. You will roll
> > toward the side being acted on by the spoiler.
> >
> > > I mean where you have no apparent
> > > positive G's in the seat or positive angle of attack.
> >
> > The wings don't much care what your seat is feeling, just what it sees
> > as the air flows over it.
>
> The whole point is the ZERO LIFT scenario. Zero angle of attack, or
> whatever it takes. No lift to roll the non spoilered wing around. That
> is what the knife edge or zero G talk is aiming at, although any
> attempt at brevity gets it taken the wrong way.
Your orientation has nothing to do with whether or not the wing produces
lift or not. Air speed and angle of attack relative to the wing does.
Spoilers aren't magic, they're just another way to control lift produced
by a wing.
If you're in a state where your spoiler-based roll control won't work,
neither would aileron-based roll control.
bbrought
> How the heck can spoilerons work if you are accidentally set sideways
> in a storm cloud or whatever? I mean where you have no apparent
> positive G's in the seat or positive angle of attack. It only works
> from the principle of milking existing positive G (from the opposite
> wing) to induce roll, so should have almost no effect in recovering
> from 90 degrees or even rolling a level aircraft doing a vomit comet
> arc... when both invoke zero G. It may have a slightly useful effect
> when an aircraft is steady state upside down, but on-edge it's only
> effect would seem to be a touch of yaw from parasitic drag. Regardless
> of induced vs parasitic drag, an aileron will act like a fin and be
> effective regardless of apparent gravity.
I think what confuses you is the part where you seem to believe the
wing has to be generating positive lift for the spoilerons to work.
All you need is a rolling moment, and this will come regardless of
your attitude and the amount of lift the wing is producing. When the
aircraft is inverted, for example, the spoilerons work very much like
split flaps on the side where they are deflected. In other words, they
have an effect vaguely similar to changing the camber of the wing in a
negative sense, which will always produce some force regardless of
what the lift coefficient on the wing was at the moment where the
spoilerons were extended. Maybe the confusion comes from the word
"spoileron" - the name probably comes from the fact that it initially
spoils the existing lift on the wing if the wing was at a high lift
coefficient or angle of attack. However, on an unloaded wing (aircraft
in a vertical dive for example or your example of the aircraft in a
knife-edge situation), the effect is like a split flap where it
generates a rolling moment still in the correct sense. On a wing at a
negative lift coefficient (aircraft that is inverted), it also works
like a split flap and continues to generate a moment in the correct
sense. How large these rolling moments are depends on the size of the
spoilerons and their locations (both spanwise and chordwise), and it
may vary quite a lot as a function of the lift coefficient/angle of
attack - so that the moment will probably vary a bit as you complete a
360 degrees roll. The sense of the moment usually remains correct for
a fully extended spoileron though.
Ed Rasimus
I suppose at this point it would really confuse the issue if I
mentioned the capability to roll quite rapidly and effectively without
the use of ANY lift enhancing or destroying device and without the
use of ANY drag creating device and without the use of puffers or
thrusters.
To end some confusion:
Ailerons are camber changing devices. By changing the camber, they
increase the amount of lift when deflected downward and thereby lift
that wing around the longitudinal access of the aircraft. But, the
downward deflected aileron creates drag which yaws the nose the
opposite direction.
Spoilers are lift-killing devices or drag creators. They destroy the
lift on one side while then allowing the more effective other wing to
rise.
Spoilerons are composite surfaces that function both as ailerons and
spoilers--usually proportional with more deflection in the spoiler
role and less in the aileron function.
The rolling I mentioned at the beginning? Pure rudder rolls. Swept
wing aircraft at high AOA can roll very effectively with no spoiler or
aileron input (in some aircraft like the F-100, the input of aileron
at high AOA can cause violent departure).
High AOA, stick neutral, full rudder in the direction of roll. The
aircraft yaws causing outboard wing to advance into the airflow and
create more lift. Retreating wing moves backward and is less effective
because of chordwise airflow. Roll till you get sick.
Dudley Henriques
> In article <sehix-AC67D8.16423819102...@nntp.aioe.org>,
> Steve Hix <se...@NOSPAMmac.comINVALID> wrote:
You beat me on this by 10 seconds Steve :-))))))))))))
Dudley Henriques
Steve Hix
<fea05d9b-172c-40e6...@d34g2000vbm.googlegroups.com>,
Dudley Henriques <dhenr...@rcn.com> wrote:
Good thing that I got up early that morning. :}
dumbstruck
> The rolling I mentioned at the beginning? Pure rudder rolls. Swept
> wing aircraft at high AOA can roll very effectively with no spoiler or
> aileron input (in some aircraft like the F-100, the input of aileron
> at high AOA can cause violent departure).
>
> High AOA, stick neutral, full rudder in the direction of roll. The
> aircraft yaws causing outboard wing to advance into the airflow and
> create more lift. Retreating wing moves backward and is less effective
> because of chordwise airflow. Roll till you get sick.
The flip side of that principle that allows delta shaped hang gliders
to correct yaw, even though they have no rudder. Any disturbance that
yaws them will cause the advancing wing to present itself to the
airflow as less swept and longer, and the opposite with the receding
wing. This will lift the advancing wing and drag it back. The
accidental roll can be snuffed out with lateral weight shift.
But I think pure rudder rolls should also work with non-swept high
dihedral aircraft. Maybe the closest thing to that I have flown is a
piper cherokee, but never tried rudder only.
dumbstruck
> dumbstruck <dumbst...@gmail.com> wrote:
> > The whole point is the ZERO LIFT scenario. Zero angle of attack, or
> > whatever it takes. No lift to roll the non spoilered wing around. That
> > is what the knife edge or zero G talk is aiming at, although any
> > attempt at brevity gets it taken the wrong way.
>
> Your orientation has nothing to do with whether or not the wing produces
> lift or not. Air speed and angle of attack relative to the wing does.
>
> Spoilers aren't magic, they're just another way to control lift produced
> by a wing.
>
> If you're in a state where your spoiler-based roll control won't work,
> neither would aileron-based roll control.
Did you read my first line quoted above? It was precisely to focus in
on AOA because the attitude discussion brings in too many digressions
(although ultimately important to application in real flight
regimes).
Assume the tailplane has depressed the main wing AOA to liftless.
Ailerons can work easily here, even on one side alone. They can adjust
the zero lift situation to positive lift or negative lift. But why do
you think a spoileron can do this. It is simply designed to kill lift,
not to exert a force this way or that.
Now assume the tailplane has depressed the main wing AOA to negative
lift. What does the spoileron do (besides drag a bit) and why? Maybe
not much. It is designed to disturb a flow on one precise airfoil
location that is critical to affect lift, a particular side of the
airfoil in respect to lift and a particular chordwise location where
stall separation is initiated. Did you look at the P61 wiki article I
posted and it's description or high res photos of spoileron location?
Quite well placed relative to these wind tunnel displays of stalling
in http://www.youtube.com/watch?v=6UlsArvbTeo
dumbstruck
> I think what confuses you is the part where you seem to believe the
> wing has to be generating positive lift for the spoilerons to work.
Agreed, although I may not be the confused party in this debate.
> All you need is a rolling moment, and this will come regardless of
> your attitude and the amount of lift the wing is producing. When the
Agreed, although spoilerons may not be effective without positive
lift.
> aircraft is inverted, for example, the spoilerons work very much like
> split flaps on the side where they are deflected. In other words, they
> have an effect vaguely similar to changing the camber of the wing in a
> negative sense, which will always produce some force regardless of
> what the lift coefficient on the wing was at the moment where the
> spoilerons were extended. Maybe the confusion comes from the word
Why? Spoilerons are mid chord, not rearward like a flap. That distends
the airfoil in a "lift enhancing" camber enhancing form, even though
it's effect is the opposite.
> "spoileron" - the name probably comes from the fact that it initially
> spoils the existing lift on the wing if the wing was at a high lift
> coefficient or angle of attack. However, on an unloaded wing (aircraft
> in a vertical dive for example or your example of the aircraft in a
> knife-edge situation), the effect is like a split flap where it
> generates a rolling moment still in the correct sense. On a wing at a
> negative lift coefficient (aircraft that is inverted), it also works
> like a split flap and continues to generate a moment in the correct
> sense. How large these rolling moments are depends on the size of the
> spoilerons and their locations (both spanwise and chordwise), and it
> may vary quite a lot as a function of the lift coefficient/angle of
> attack - so that the moment will probably vary a bit as you complete a
> 360 degrees roll. The sense of the moment usually remains correct for
> a fully extended spoileron though.
You are bringing in speculation on how a mid chord upper surface
spoileron works when not at positive AOA. Why is everyone so negative
and patronizing to me, yet can offer no citation or even plausible
reason why they should work in these weird regimes other than voodoo
aerodynamics? On most aviation forums, by now someone would have
popped a spoileroned airfoil into a virtual PC windtunnel and charted
a polar diagram extending to minus AOA, but I don't think there is a
Mac version that will work for me. BTW, P61 spoilerons were 1/3 chord
from the trailing edge, and ran half the length of the outer wing.
Steve Hix
<27932485-5f58-45bf...@f18g2000prf.googlegroups.com>,
dumbstruck <dumb...@gmail.com> wrote:
If you haven't done them recently, try doing some falling leaf practice.
Might could be worth bringing an instructor along for the first time.
Roughly, set up for power-on stall work, and hold the aircraft just
above the stall point, stick aft, aileron neutral. When it tries to fall
off to either side, "step on the upper wing" with the rudder, to bring
wings level, do *not* use aileron. Fun.
I was introduced to them last year when I got back into flying by the
instructor who checked me out.
bbrought
> You are bringing in speculation on how a mid chord upper surface
> spoileron works when not at positive AOA. Why is everyone so negative
> and patronizing to me, yet can offer no citation or even plausible
> reason why they should work in these weird regimes other than voodoo
> aerodynamics?
I am not speculating at all - I am basing it on my experience of
testing various spoiler configurations in wind tunnels. Unfortunately
the work was done for a company and company confidential, otherwise I
would have posted the results.
However, since you insist on a citation, have a look in Hoerner's book
on Fluid Dynamic Lift. On p 10-15, Figure 16 is shown an example of a
symmetrical airfoil (NACA 65A006) at zero angle of attack and a Mach
number of 0.6. The example has a spoiler at 50% chord, which results
in a CL = -0.3 (negative lift coefficient). So, I repeat:
- zero angle of attack,
- symmetrical aerofoil,
- spoiler at 50%,
- CL = -0.3.
I don't think it can be more clear than that.
Hoerner also comments on spoilers on thin aerofoils, and I quote:
*******
Figure 16 presents the lift effectiveness of a "spoiler" flap
(simulated by a triangular ridge) extended from the upper side of a
thin and straight foil section. The lift differential produced is:
(a) comparatively small
(b) nearly independent of angle of attack
(c) comparatively independent of location along chord
*******
and further down:
*******
It may thus seem to be possible to use a spoiler, for example, in a
horizontal tail surface, and they have indeed been used (or proposed
to be used) in the control surfaces of missiles (possibly for reasons
other than aerodynamic). We will see, however, that spoilers can be
used more profitably in combination with round-nosed and cambered foil
sections that exhibit trailing edge stalling as in wings, and they are
then used for lateral control.
*******
Notice point (b), which is what you dispute. I would actually like to
ask you what real data you were using for your argument that a
spoileron doesn't work at zero angle-of-attack?
Point (c) is my response to your other comment:
> Why? Spoilerons are mid chord, not rearward like a flap. That distends
> the airfoil in a "lift enhancing" camber enhancing form, even though
> it's effect is the opposite."
The mechanism that is used by a spoileron on top of the wing and a
flap on the bottom of the wing is very similar, except that a
spoileron operates on what is usually the suction side of the
aerofoil. The effects are not opposite, both generate a force in the
opposite direction to which they are deflected:
- a spoileron on top of the wing generates a negative lift
coefficient, or subtracts from the lift coefficient of the wing before
deflection
- a split flap on the bottom of the wing generates a positive lift
coefficient, or adds to the lift coefficient of the wing before
deflection
Both of them also produce a lot of drag, of course.