On Mar 13, 8:45*pm, Z Goudie wrote:
At 21:55 13 March 2009, The Real Doctor wrote:

How much extra lift do you think is required to climb?

Without going into the math (euphemism for I'm not sure how to!).

If you are not sure how to do the math, how can you be sure that you
are correct ?

In fact, I am able to do the math ( practicing aero engineer) and you
are not correct. The difference between lift ( and thus angle of
attack ) in a STEADY descent and a STEADY climb is practically non
existent.

To do the math, you should draw out a diagram of the drag, lift,
weight and towline. The aircraft is climbing on a line that is an
angle "gamma". Draw the towline force on this line pulling the
aircraft forward and up. Draw the drag in the opposite direction.
Draw lift at a right angle to this line and finally draw weight
pulling straight down.

Total up these 4 forces and making them balance out in the up-down and
forward-back directions gives you the relationship that lift = cosine
( gamma ) * weight. The steeper you climb, then less the lift !!!

If you make different assumption of the direction of the towplane
force, then you would get a different result.


Todd Smith
3S