Landing on a sloping runway with different wind velocities

"Tony Cox" wrote in message
ups.com...
[...]
Tony, in "Mountain Flying Bible" the author Sparky Imeson was once
discussing this and a physics professor handed him a formula which is
published in that book. It is the beakeven wind speed for taking off
uphill
into wind and downhill with a tailwind. Hopefully it formats correctly
here.
If wind is less, takeoff downhill and if more take off uphill.

Vbe = (s * d) / 5 * V

[...]

Vbe = (2*900)/5 * 60 = 21600

Seems a bit high to me. Perhaps Sparky meant

Vbe = (2*900)/(5*60) = 6 knots.

Well, I suppose its possible, but I'd have thought the
figure a little on the low side.

I'd be suspicious of a formula given without any explanation of its
derivation. This formula in particular seems odd, as the break-even wind
speed as interpreted by you decreases as takeoff speed goes up. This is
opposite what I'd have intuitively thought (that is, an airplane with a
higher takeoff speed is less-affected by wind, requiring higher wind speed
before it matters which way one takes off).

That suggests that maybe the formula as given in the previous post is
correct (that is, you really do multiply the (s * d) / 5 by V) and that the
units are what are missing. Though, why a formula would be given that
requires a unit conversion rather than just including the conversion factor
in the formula, I can't say.

The other thing I'd point out is that even if the formula is correct, it's
obviously an approximation, as the term taking into account runway slope is
stated to be in degrees, but is used in a linear fashion (rather than using
some trigonometric function).

Since you have a copy of Imeson's book, perhaps you'll be able to find the
same formula and see whether the previous post left out some important
information given in the book. Otherwise, I'm not sure I see how to apply
the formula. You make a reasonable attempt to get the result into some
sensible magnitude, but it changes the formula in a way so as to make it
counter-intuitive as to how it applies to different airplanes of different
capabilities.

Pete