leading edge flaps

On Sun, 11 Jan 2004 20:14:26 GMT, "John R Weiss"
wrote:

"Dudley Henriques" wrote...

The Blues bolted 'um shut. Can you imagine what would happen in a tight
diamond with an A4 if a wing position got an asymmetrical slat extension
with roll induced....say in a barrel roll? Not a pretty thought!! :-))

In over 1700 A-4 hours, I never had an asymmetric slat extension that I could
not quickly and easily control. After about 1000 hours, few of them were even
unpredictable...

I wonder if you could try to describe, as well as you can recall, what
exactly happens during an asymmetrical slat extension?

The reason I am asking such an obvious sounding question is that we
recently had a discussion concerning asymmetric slat extension of a
BF-109 in a Finnish newsgroup. While the immediate lay-man's reaction
is that the aircraft would, of course, violently roll away from the
extended slat (=extended slat up), because of the increased lift by
the slat, the situation becomes less obvious the more I think about
it.

Theoretically, from the textbook figure illustrating the effect of
trailing edge flaps and leading edge slats, one could argue that
nothing happens, since slats (unlike flaps) do not increase Lift
Co-efficient (CL) on a given Angle of Attack (AOA) but only increase
the maximum attainable CL. This at least in the case that the net wing
area does not increase when slat extends.

If the wing area increases (as probably is the case with A-4, judging
from the photo I have) as the slat extends, the aircraft would tend to
roll extended slat up. Right?

However, if the geometry is such that the leading edge moves down as
the slat extends, one could argue that the AOA of the profile
decreases causing roll towards the extended slat.

Or, if the slat extension causes a change of pressure distribution
around the aileron (the aileron snatch reported by the British BF-109
test pilots ?) moving the ailerons (probably not on the hydraulic
irreversible(?) control system of the A-4) until the pilot corrects
it, the roll could be either way.

Mikko