Control Reversal in WWII

In discusing the characteristics of how the Me 109K should be flown
against the P51 Mustang and P47 the issue of control reversability
came up. Would someone be able to expand on control reversability.

The Me 109 G10 and Me 109 K4 (G14 was a stopgap due to engine delays
in the G10)had a powerfull engine that allowed them to do a speed of
458mph and outclimbe all allied aircraft. However the old crate had
an old wing section that created enormous aileron forces for the
pilot; also becuase the the small Me 109 cockpit a pilot could
generate only 40lbs of joystick force could have generated 60lbs of
force in a P51. As a result only 2-3 degree of airleron deflection
was possible at 400mph the 109 had a roll rate of 45 degrees/second.
A FW190A and even a P47 could have managed nearly 180 degrees in that
time.

The issue of control reversability then came up. If power ailerons
were fited to the Me 109 they would have allowed a greater deflection
but would this have caused control reversability at some point as the
wing twisted and the ailerons acted more like trim tabs?

What causes reversability? Why is a slab elevator sometimes used?

I've also heard of WW2 pilots using trim tabs to pull out of a dive or
get an aircraft rightway up. What were they doing?

The P38 had a smaller turning circle than the Me 109 (presumably at
lower speeds of around 300mph) but its roll rate was even worse than
the 109 and this is how 109s escaped P38s and I note that some late
war P38s received power controls.

In article ,
(Eunometic) wrote:

In discusing the characteristics of how the Me 109K should be flown
against the P51 Mustang and P47 the issue of control reversability
came up. Would someone be able to expand on control reversability.

The Me 109 G10 and Me 109 K4 (G14 was a stopgap due to engine delays
in the G10)had a powerfull engine that allowed them to do a speed of
458mph and outclimbe all allied aircraft. However the old crate had
an old wing section that created enormous aileron forces for the
pilot; also becuase the the small Me 109 cockpit a pilot could
generate only 40lbs of joystick force could have generated 60lbs of
force in a P51. As a result only 2-3 degree of airleron deflection
was possible at 400mph the 109 had a roll rate of 45 degrees/second.
A FW190A and even a P47 could have managed nearly 180 degrees in that
time.

The issue of control reversability then came up. If power ailerons
were fited to the Me 109 they would have allowed a greater deflection
but would this have caused control reversability at some point as the
wing twisted and the ailerons acted more like trim tabs?

What causes reversability? Why is a slab elevator sometimes used?


Two things: You hit the first one above: aeroelasticity.

The second is localized Mach 1+ velocities, which can cause shockwaves
on the upper surface of, say, a wing. The result is a pressure higher
than that on the bottom surface. A subsequent dive results.

Even modern aircraft can suffer from #2. If they cruise at very high
altitude, where their critical Mach number is near cruise and stall is
close, too, any changes in velocity have to be within those limits, or
an uncontrolled descent is in the works, until Mach number recedes, or
the ground intervenes.




I've also heard of WW2 pilots using trim tabs to pull out of a dive or
get an aircraft rightway up. What were they doing?

The P38 had a smaller turning circle than the Me 109 (presumably at
lower speeds of around 300mph) but its roll rate was even worse than
the 109 and this is how 109s escaped P38s and I note that some late
war P38s received power controls.

On 19 Jun 2004 19:43:08 -0700, (Eunometic)
wrote:

Why is a slab elevator sometimes used?

If you mean a horizontal stabilizer that changes angle (in contrast to
trim tabs), it's a very old concept. The Piper Cub works that way. You
have a trim handle like a window crank. Roll it and you turn an
endless cable that turns a jack-screw (worm gear) which raises or
lowers the front of the stabilizer.

all the best -- Dan Ford
email: (put Cubdriver in subject line)

The Warbird's Forum www.warbirdforum.com
The Piper Cub Forum www.pipercubforum.com
Viva Bush! weblog www.vivabush.org

"Cub Driver" wrote in message
...
On 19 Jun 2004 19:43:08 -0700, (Eunometic)
wrote:

Why is a slab elevator sometimes used?

If you mean a horizontal stabilizer that changes angle (in contrast
to
trim tabs), it's a very old concept. The Piper Cub works that way.
You
have a trim handle like a window crank. Roll it and you turn an
endless cable that turns a jack-screw (worm gear) which raises or
lowers the front of the stabilizer.

I was thinking of an all moving surface. I think its sometimes
refered to as an all flying tailplane as in an F4.

From what i understand: the Cub has a tailplane that changes angle as
well as having elevators.

I guess I wanted to know if the all moving and flying tailplane
combated control stifness or reversal by its absence of elevators by
some aerodynmic effect or whether it was a way of eliminating
aeroelastic twisting.

I guess if WW2 Spitfires had cub like tailplanes some enterprising
pilot would have cranked himself out of a transonic dive.




all the best -- Dan Ford
email: (put Cubdriver in subject line)

The Warbird's Forum www.warbirdforum.com
The Piper Cub Forum www.pipercubforum.com
Viva Bush! weblog www.vivabush.org

"Orval Fairbairn" wrote in
message
news
In article ,
(Eunometic) wrote:

In discusing the characteristics of how the Me 109K should be
flown
against the P51 Mustang and P47 the issue of control reversability
came up. Would someone be able to expand on control
reversability.

The Me 109 G10 and Me 109 K4 (G14 was a stopgap due to engine
delays
in the G10)had a powerfull engine that allowed them to do a speed
of
458mph and outclimbe all allied aircraft. However the old crate
had
an old wing section that created enormous aileron forces for the
pilot; also becuase the the small Me 109 cockpit a pilot could
generate only 40lbs of joystick force could have generated 60lbs
of
force in a P51. As a result only 2-3 degree of airleron
deflection
was possible at 400mph the 109 had a roll rate of 45
degrees/second.
A FW190A and even a P47 could have managed nearly 180 degrees in
that
time.

The issue of control reversability then came up. If power
ailerons
were fited to the Me 109 they would have allowed a greater
deflection
but would this have caused control reversability at some point as
the
wing twisted and the ailerons acted more like trim tabs?

What causes reversability? Why is a slab elevator sometimes
used?


Two things: You hit the first one above: aeroelasticity.

Thanks, you've given me some terms I can use to do further research.


The second is localized Mach 1+ velocities, which can cause
shockwaves
on the upper surface of, say, a wing. The result is a pressure
higher
than that on the bottom surface. A subsequent dive results.

Even modern aircraft can suffer from #2. If they cruise at very high
altitude, where their critical Mach number is near cruise and stall
is
close, too, any changes in velocity have to be within those limits,
or
an uncontrolled descent is in the works, until Mach number recedes,
or
the ground intervenes.

Like the U2. There is a sailplane called Perlan which will
experience this coffin corner phenomena soon,

The B-47 had neutral aileron control at about 425 knots (as I seem to
remember). Above that speed it rolled in the opposite direction than the
control input. It was because of the flexible wing. Approaching 425 (if
that's the right speed), the roll produced by aileron input reduced to no
roll at all at 425, then it would roll opposite the control input above 425.
It was, as you noted, because, above 425, the aileron served merely as a tab
which ended up twisting the overall wing in the opposite control direction.

--

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

"Eunometic" wrote in message
om...
In discusing the characteristics of how the Me 109K should be flown
against the P51 Mustang and P47 the issue of control reversability
came up. Would someone be able to expand on control reversability.

The Me 109 G10 and Me 109 K4 (G14 was a stopgap due to engine delays
in the G10)had a powerfull engine that allowed them to do a speed of
458mph and outclimbe all allied aircraft. However the old crate had
an old wing section that created enormous aileron forces for the
pilot; also becuase the the small Me 109 cockpit a pilot could
generate only 40lbs of joystick force could have generated 60lbs of
force in a P51. As a result only 2-3 degree of airleron deflection
was possible at 400mph the 109 had a roll rate of 45 degrees/second.
A FW190A and even a P47 could have managed nearly 180 degrees in that
time.

The issue of control reversability then came up. If power ailerons
were fited to the Me 109 they would have allowed a greater deflection
but would this have caused control reversability at some point as the
wing twisted and the ailerons acted more like trim tabs?

What causes reversability? Why is a slab elevator sometimes used?

I've also heard of WW2 pilots using trim tabs to pull out of a dive or
get an aircraft rightway up. What were they doing?

The P38 had a smaller turning circle than the Me 109 (presumably at
lower speeds of around 300mph) but its roll rate was even worse than
the 109 and this is how 109s escaped P38s and I note that some late
war P38s received power controls.

The Navy FJ-3 Fury carrier based fighter of the late 1950s suffered from
control reversal. In a dive as it approached Mach 1 when the stick was put
over to one side the plane rolled rapidly, but in the opposite direction
from that intended! The FJ-3 ailerons extended out to the tips the wings.
Consequently at near sonic Mach putting the aileron down resulted in the
wing warping such that the net lift force was opposite to what was expected.
The problem was fixed in the FJ-4 by designing the ailerons to not extend to
the wing tips.

Interestingly, The Navy FJ series fighters were an outgrowth of the famous
Korean War Air Force F-86, which in turn was an outgrowth of an earlier Navy
fighter, the FJ-1, a straight wing jet powered plane that the Navy deployed
in one squadron before going with the FH-1 (the granddaddy of the equally
famous Vietnam War F-4 Phantom). North American Aircraft Company made use of
Nazi World War II engineering test data to develop the swept wings they
fitted to the Navy FJ-1 to create the Air Force F-86. This is the same North
American Aircraft Company that built more World War II aircraft than all
other aircraft companies, the largest number being the B-25 medium bomber.

WDA

end



"Orval Fairbairn" wrote in message
news
In article ,
(Eunometic) wrote:

In discusing the characteristics of how the Me 109K should be flown
against the P51 Mustang and P47 the issue of control reversability
came up. Would someone be able to expand on control reversability.

The Me 109 G10 and Me 109 K4 (G14 was a stopgap due to engine delays
in the G10)had a powerfull engine that allowed them to do a speed of
458mph and outclimbe all allied aircraft. However the old crate had
an old wing section that created enormous aileron forces for the
pilot; also becuase the the small Me 109 cockpit a pilot could
generate only 40lbs of joystick force could have generated 60lbs of
force in a P51. As a result only 2-3 degree of airleron deflection
was possible at 400mph the 109 had a roll rate of 45 degrees/second.
A FW190A and even a P47 could have managed nearly 180 degrees in that
time.

The issue of control reversability then came up. If power ailerons
were fited to the Me 109 they would have allowed a greater deflection
but would this have caused control reversability at some point as the
wing twisted and the ailerons acted more like trim tabs?

What causes reversability? Why is a slab elevator sometimes used?


Two things: You hit the first one above: aeroelasticity.

The second is localized Mach 1+ velocities, which can cause shockwaves
on the upper surface of, say, a wing. The result is a pressure higher
than that on the bottom surface. A subsequent dive results.

Even modern aircraft can suffer from #2. If they cruise at very high
altitude, where their critical Mach number is near cruise and stall is
close, too, any changes in velocity have to be within those limits, or
an uncontrolled descent is in the works, until Mach number recedes, or
the ground intervenes.




I've also heard of WW2 pilots using trim tabs to pull out of a dive or
get an aircraft rightway up. What were they doing?

The P38 had a smaller turning circle than the Me 109 (presumably at
lower speeds of around 300mph) but its roll rate was even worse than
the 109 and this is how 109s escaped P38s and I note that some late
war P38s received power controls.

On Sun, 20 Jun 2004 14:39:59 GMT, "Eunometic"
wrote:

From what i understand: the Cub has a tailplane that changes angle as
well as having elevators.

Yes, that's right. Forget I spoke!

all the best -- Dan Ford
email: (put Cubdriver in subject line)

The Warbird's Forum www.warbirdforum.com
The Piper Cub Forum www.pipercubforum.com
Viva Bush! weblog www.vivabush.org

"Darrell" wrote in message
news:FAjBc.20218$ey.9317@fed1read06...
The B-47 had neutral aileron control at about 425 knots (as I seem to
remember). Above that speed it rolled in the opposite direction than the
control input. It was because of the flexible wing. Approaching 425 (if
that's the right speed), the roll produced by aileron input reduced to no
roll at all at 425, then it would roll opposite the control input above
425.
It was, as you noted, because, above 425, the aileron served merely as a
tab
which ended up twisting the overall wing in the opposite control
direction.


I believe that the B-47 aileron control characteristics you mention are
close to the facts, and I recall that the "red-line" speed vs roll control,
was handled in a rather unusual manner.

During the late 1950's, some B-47 units were tasked to fly low level
"LABS" missions. At some speed near the "red-line" (it could have been 425,
it was long ago!), the wing twist would cause one wing or the other to
become increasingly "heavy", and increased roll trim would have to be
cranked in to maintain level flight. Each aircraft was slightly different
than others, so an aileron rerigging program was begun, to rerig all ships
ailerons to near perfection and then test fly each one to determine how much
aileron trim was required to maintain level flight at some speed (I thought
it was higher than 425, but hey, that was in maybe 1958 or so). Then, if
more than 20 (?) units of trim were required, the aileron of the "heavy"
wing was carefully rerigged a couple of degrees below neutral, and the test
flight was repeated.

This process went on until all the 303rd Bomb Wing ships except one met
the new criteria. The one that did not respond got a meticulous (sp?)
alignment check, and one wing was found to have a permanent twist, exceeding
the -3 structural manual's service limits. Deep down in the procurement
documents it was found that that particular ship's right wing was out of lim
its when accepted by the AFPRO from Boeing.

Old Chief Lynn

"Darrell" wrote in message
news:FAjBc.20218$ey.9317@fed1read06...
The B-47 had neutral aileron control at about 425 knots (as I seem to
remember). Above that speed it rolled in the opposite direction than the
control input. It was because of the flexible wing. Approaching 425 (if
that's the right speed), the roll produced by aileron input reduced to no
roll at all at 425, then it would roll opposite the control input above
425.
It was, as you noted, because, above 425, the aileron served merely as a
tab
which ended up twisting the overall wing in the opposite control
direction.

I believe that the B-47 aileron control characteristics you mention are
close to the facts, and I recall that the "red-line" speed vs roll control,
was handled in a rather unusual manner.

During the late 1950's, some B-47 units were tasked to fly low level
"LABS" missions. At some speed near the "red-line" (it could have been 425,
it was long ago!), the wing twist would cause one wing or the other to
become increasingly "heavy", and increased roll trim would have to be
cranked in to maintain level flight. Each aircraft was slightly different
than others, so an aileron rerigging program was begun, to rerig all ships
ailerons to near perfection and then test fly each one to determine how much
aileron trim was required to maintain level flight at some speed (I thought
it was higher than 425, but hey, that was in maybe 1958 or so). Then, if
more than 20 (?) units of trim were required, the aileron of the "heavy"
wing was carefully rerigged a couple of degrees below neutral, and the test
flight was repeated.

This process went on until all the 303rd Bomb Wing ships except one met
the new criteria. The one that did not respond got a meticulous (sp?)
alignment check, and one wing was found to have a permanent twist, exceeding
the -3 structural manual's service limits. Deep down in the procurement
documents it was found that that particular ship's right wing was out of lim
its when accepted by the AFPRO from Boeing.

Old Chief Lynn