Thinking about stalls

On Mar 14, 9:59*am, Jim Logajan wrote:
WingFlaps wrote:
On Mar 14, 9:33*am, Jim Logajan wrote:
WingFlaps wrote:
On Mar 14, 9:11*am, Brian wrote:
As for your question above, given that the airplanes are ascending
or decending at constant rates then the lift is equal to the
wieght of the airplane in both cases. If the aircraft are the same
wieght then the lift generated will be the same.

That is not correct.

Hmmm. Brian's statement appears essentially correct - and you are
correct too. The "gotcha" is that the vertical component of the lift
force exceeds

the weight only during the transition from level flight to constant
ascending flight. And the lift force is less than the weight during
the transition from level flight to constant descending flight.

But once the vertical speed becomes constant (whether up or down) the
vertical component of lift has to equal the downward force of
gravity. If it didn't, then the aircraft would begin _accelerating_
up or down, depending on the difference.

Nope, if the airspeed is constant, the lift from the two wings is not
the same. This is thought provoking discussion I was hoping to start!
Can you see why lift does not equal weight in both cases?

I don't wish to be confrontational since you are looking for thought
provoking discussion, but I am pretty sure there is a fair amount of
imprecision, and therefore ambiguity, in your statements. This tends to
make it difficult to get very far in these discussions.

Would it help any if I presented the 2-D equations of force involved?
And perhaps you could do the same?- Hide quoted text -


Sure here you go:
D=drag
L=lift
W=weight
T=thrust
alpha=angle of thrust

For no acceleration in any plane:

W=Tsin(alpha) + L
D=Tcos(alpha)

What you and many other texts have missed is that the thrust angle
changes...
What this means is that when you make a plane climb at constant speed
you are deliberately reducing lift from from the wing and supplanting
it with engine thrust! To extend this idea further, it is not the
climb per se that may be the problem but a decaying airspeed... The
above equations can be extended to the AOA and airspeed but the
conclusion remains the same.

Now, what about that tricky updraft? Is this thought provoking :-)

Cheers