"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,