Windy & Challenging Short Field Takeoff

[FlyingMonkey]

I recently had a challenging short(ish) field situation when we went down to Agua Caliente Hot Springs for a fun day, documented in this video along with some family fun.

 

[PeterNSteinmetz]

I don’t think I would have done that with family on board. Solo possibly. Any degree of sink or a sudden drop in tailwind and it would have been in the weeds. Deserts produce a lot of thermals with strong updrafts and downdrafts.

 

[PeterNSteinmetz]

I’m not following the physics here. How would a drop in tailwind effect lift?

Good catch as I may have gotten the sign of the change wrong. I believe an increase in tailwind would decrease lift, not the other way around.

Essentially it is a wind shear situation. The plane has a certain momentum and if the wind abruptly changes it takes a bit for the plane to adjust to that. During the transition the relative wind over the wings will decrease and lift will decrease.

 

[PeterNSteinmetz]

I'm with you. But, once in the air, I don't think there's any different between a tail wind and a head wind as far as sheer is concerned. Sheer is sheer.

I agree you can achieve an apparent loss in performance with either a headwind or a tailwind changing, but the direction of the change in wind speed is different - right ?

In other words, increased tailwind or decreased headwind = apparent loss of performance. And vice versa, decreased tailwind or increased headwind = apparent increase in performance. Temporarily.

 

[PeterNSteinmetz]

Agreed. But all that is true no matter if you started with a headwind or tailwind. I don't think starting with a tailwind makes sheer any worse or better. It just is what it is.

Good point. I guess the one net difference practically might have been that if he had started into the wind he may have been more likely to be over the runway when dealing with a shear event. Not sure how much difference it would have made in time over the desert close to the ground.