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.