On 2006-10-10, Edwin Johnson wrote:
On 2006-10-09, Tony Cox wrote:
Here's a problem which seems to have a non-trivial solution.
At least, I've not been able to find a definitive answer to it, but
what do I know??

Rule of thumb responses are interesting, but better would be
a full mathematical treatment. Presumably, a proper treatment

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

Whe
Vbe = breakeven speed in knots
s = slope up in degrees
d = POH distance to liftoff with 0 slope and 0 wind in feet
V = volocity of liftoff speed in knots TAS

OK Guys, there is supposed to be parentheses around the last two symbols, as:

Vbe = (s * d) / (5 * V)

5 = a constant
d = POH distance to liftoff with 0 slope and 0 wind (in feet) under the
existing density altitude condition

After seeing the discussion, it ocurred to me that I should have listed
page, etc. The book is copyrighted in 1998, says:

First Edition
First printing: November 1998

The formula is on page 2-43.

If this formula isn't found in subsequent editions, perhaps Sparky decided
it might not be wise to put it in for various reasons. I'm just passing
along the info in my edition and have seen no other editions.

....Edwin
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