Use of flaps during heavy crosswinds

[BaronPete]

The HP question isn't my field, maybe one of the mechanics here can give some more information. Lower RPM is certainly less horsepower (work/time), but how much I would have no clue.

For your losing airspeed, I suggest you read into wind sheer a little bit. Gusty conditions imply wind will increase and decrease rapidly, right? So you are flying along at 50 knots with the wind at 20 knots. Now the wind picks up to 30, putting your airspeed at 60, to counter this you slow down back to 50. Now you are at 50 knots with 30 knots of wind and suddenly the wind dies back down to 20 knots, now your airspeed is 40 knots. That was the scenario I was referring too, pitch isn't a factor but instead the sudden loss of windspeed.

I mean I'm aware (or thought I was) of wind shear and it being the reason behind carrying some extra speed when landing in windy conditions, but it seems almost like we're talking groundspeed here. If I'm flying at 60 knots and get a gust in the face of 20 knots, it doesn't seem to me that the ASI would drop to 40. Isn't the relative wind still producing the same amount of lift, if not more, provided your AoA hasn't changed?

I really hate to think someone needs a crayon box to break this down for me, but I feel it's worth asking.

 

[shdw]

I mean I'm aware (or thought I was) of wind shear and it being the reason behind carrying some extra speed when landing in windy conditions, but it seems almost like we're talking groundspeed here. If I'm flying at 60 knots and get a gust in the face of 20 knots, it doesn't seem to me that the ASI would drop to 40. Isn't the relative wind still producing the same amount of lift, if not more, provided your AoA hasn't changed?

I really hate to think someone needs a crayon box to break this down for me, but I feel it's worth asking.

It could also be my method of explanation, so let's try something different. We are not talking ground speed at all, instead it is flight speed through the air as that is all that matters, right? I mean in a 50 knot wind we can be flying at 50 with a ground speed of zero and still not stall.


Let's park the airplane on the ground and face it into the wind. Now let's turn on a big fan that blows air at 20 knots over the wings, this is similar to an aircraft flying at 20 knots (if it could actually do this). Now imagine we turn the fan off, the aircraft is now back at zero, right?

Time to take this and apply it to an aircraft in the air. You are flying forward through the air at 50 knots of airspeed with that fan blowing in your face. Now someone pulls the plug on you, what would happen to your airspeed? Well with the fan off, 20 knots of airflow is no longer being blown into the airplane so the result would be an airplane flying at 30 knots through the air instead of 50.

Let's reverse the scenario to flying at 50 knots with the fan off and then someone turns the fan on. Now you have an additional 20 knots of air flowing over the wing and your airspeed would pick up to 70 knots.

Again ignore ground speed in all of this. What matters is the airflow over the wing and the danger is when a gust dies down, in other words, someone turned your fan off. If you are going slow when the fans shut off you can be left dangerously close to a stalling airspeed.

 

[BaronPete]

It could also be my method of explanation, so let's try something different. We are not talking ground speed at all, instead it is flight speed through the air as that is all that matters, right? I mean in a 50 knot wind we can be flying at 50 with a ground speed of zero and still not stall.


Let's park the airplane on the ground and face it into the wind. Now let's turn on a big fan that blows air at 20 knots over the wings, this is similar to an aircraft flying at 20 knots (if it could actually do this). Now imagine we turn the fan off, the aircraft is now back at zero, right?

Time to take this and apply it to an aircraft in the air. You are flying forward through the air at 50 knots of airspeed with that fan blowing in your face. Now someone pulls the plug on you, what would happen to your airspeed? Well with the fan off, 20 knots of airflow is no longer being blown into the airplane so the result would be an airplane flying at 30 knots through the air instead of 50.

Let's reverse the scenario to flying at 50 knots with the fan off and then someone turns the fan on. Now you have an additional 20 knots of air flowing over the wing and your airspeed would pick up to 70 knots.

Again ignore ground speed in all of this. What matters is the airflow over the wing and the danger is when a gust dies down, in other words, someone turned your fan off. If you are going slow when the fans shut off you can be left dangerously close to a stalling airspeed.

I see what you're saying. I knew it couldn't be groundspeed, just needed a different picture I suppose :crazy:

 

[shdw]

I see what you're saying. I knew it couldn't be groundspeed, just needed a different picture I suppose :crazy:

That is usually the problem with instruction, we can all learn it, it just needs to be presented a different way for every student. Makes this crap difficult!

 

[Dazzler]

It could also be my method of explanation, so let's try something different. We are not talking ground speed at all, instead it is flight speed through the air as that is all that matters, right? I mean in a 50 knot wind we can be flying at 50 with a ground speed of zero and still not stall.


Let's park the airplane on the ground and face it into the wind. Now let's turn on a big fan that blows air at 20 knots over the wings, this is similar to an aircraft flying at 20 knots (if it could actually do this). Now imagine we turn the fan off, the aircraft is now back at zero, right?

Time to take this and apply it to an aircraft in the air. You are flying forward through the air at 50 knots of airspeed with that fan blowing in your face. Now someone pulls the plug on you, what would happen to your airspeed? Well with the fan off, 20 knots of airflow is no longer being blown into the airplane so the result would be an airplane flying at 30 knots through the air instead of 50.

Let's reverse the scenario to flying at 50 knots with the fan off and then someone turns the fan on. Now you have an additional 20 knots of air flowing over the wing and your airspeed would pick up to 70 knots.

Again ignore ground speed in all of this. What matters is the airflow over the wing and the danger is when a gust dies down, in other words, someone turned your fan off. If you are going slow when the fans shut off you can be left dangerously close to a stalling airspeed.

Nice explanation.

 

[saria19]

I find that it is better to teach a student to use less flaps in high winds because controlability of the aircraft is better. That is something you want, no matter what stage of your flight career you're in. More importantly, one day when that student is soloing and they run into those sorts of winds, the flight can usually be ended in a safer manner, with less fear on both sides (for both the instructor and student).