Thinking about stalls

On Mar 13, 6:45*pm, Big John wrote:
On Wed, 12 Mar 2008 17:14:17 -0700 (PDT), WingFlaps





wrote:
Hi All,

Imagine a plane in 2 conditions.

1) Climbing with full power
2) Descending fast with 50% power.

Both have constant rates of ascent and descent.

Question A: Which wing is closer to stall?
Question B: A big updraft occurs, which is more likely to stall?

If you vote first it _may_ lead to some good discussion later...

Cheers

***************************************
Obviously #2. Any one should be able to see that.


Aha, so it is closer to the stall?

Cheers

Jim Logajan wrote in
:

WingFlaps wrote:
Hi All,

Imagine a plane in 2 conditions.

1) Climbing with full power
2) Descending fast with 50% power.

Waitaminute - how can a plane be in both conditions at the same time!?


Ken can probably explain it better than anyone.


Bertie

"WingFlaps" wrote in message
...
Hi All,

Imagine a plane in 2 conditions.

1) Climbing with full power
2) Descending fast with 50% power.

Both have constant rates of ascent and descent.

Question A: Which wing is closer to stall?
Question B: A big updraft occurs, which is more likely to stall?


I'm not sure if there's enough information. If it's a typical prop plant I
would expect that there would be a difference between a high wing and a low
wing due to slipstream effects, but my guess would be that the right wing
would be closer. Or, are you asking which of the two scenarios is
closer/more likely to stall. In that case, I'd say the first
configuration. Full-power departure stalls are easy to encounter.

-c

Put me in the "not enough info" column.

Plane #2 could be in fact _in_ a stall (or spin), "descending fast
with 50% power" or _more_. Think Delta Flight 191, for example.



On Mar 12, 8:14 pm, WingFlaps wrote:
Hi All,

Imagine a plane in 2 conditions.

1) Climbing with full power
2) Descending fast with 50% power.

Both have constant rates of ascent and descent.

Question A: Which wing is closer to stall?
Question B: A big updraft occurs, which is more likely to stall?

If you vote first it _may_ lead to some good discussion later...

Cheers

OK... *but is the climbing or descending wing generating the most
lift?

I agree, your original question is missing some critical information.
Such as:

1. are the airspeeds the same for each aircraft?
2. confirm that the decending aircraft is not already stalled
3. Do the airplanes weigh the same?


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.

Brian CFIIG/ASEL

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.

Cheers

On Mar 14, 4:02*am, "gatt" wrote:
"WingFlaps" wrote in message

...

Hi All,

Imagine a plane in 2 conditions.

1) Climbing with full power
2) Descending fast with 50% power.

Both have constant rates of ascent and descent.

Question A: Which wing is closer to stall?
Question B: A big updraft occurs, which is more likely to stall?

I'm not sure if there's enough information. *If it's a typical prop plant I
would expect that there would be a difference between a high wing and a low
wing due to slipstream effects, but my guess would be that the right wing
would be closer. * Or, are you asking which of the two scenarios is
closer/more likely to stall. * *In that case, I'd say the first
configuration. * *Full-power departure stalls are easy to encounter.


Ok good, but let's say both planes have the same airspeed. Does that
change anything?
Cheers

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.

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?

Cheers

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?