Upwind to downwind turn

[Cutlass1287]

I have heard people say things to the effect that if you made a "sharp" turn from an upwind heading to a downwind heading, you could stall. Im not so sure about this theory- I thought the plane didnt care about which way the wind was blowing?

[FlyChicaga]

It's not the wind. It's the SHARP turn at low speed.

[roundout]

assuming you're talking about traffic pattern ops, yes, that turn can be dangerous. you've got a low airspeed, nose high pitch attitude, a high power setting (left turning tendencies, anyone?). lots of people aren't careful to make sure this turn is coordinated.....so add that to the mix. if you stall out, you're a prime candidate to be a smoking hole in the ground.

[Cutlass1287]

I am not talking about any low speed, high angle of attack of turn, I am talking about the suggestion that a turn from an upwind heading to a downwind heading will somehow cause you to lose airspeed.

[flyover]

[ QUOTE ]
I am not talking about any low speed, high angle of attack of turn, I am talking about the suggestion that a turn from an upwind heading to a downwind heading will somehow cause you to lose airspeed.

[/ QUOTE ]

Nope, but it will increase your groundspeed. So you got that goin' for ya.

[USMCmech]

[ QUOTE ]
I am not talking about any low speed, high angle of attack of turn, I am talking about the suggestion that a turn from an upwind heading to a downwind heading will somehow cause you to lose airspeed.

[/ QUOTE ]


Very common Old Wives Tale.

Completely inaccurate, but very common. [img]/ubbthreads/images/graemlins/banghead.gif[/img] [img]/ubbthreads/images/graemlins/banghead.gif[/img] [img]/ubbthreads/images/graemlins/banghead.gif[/img]


The airplane dosent know or care which way the wind is blowing. Making the "downwind turn" doesn't do anything to the airspeed over the wings.

[Dazzler]

I was under the impression that the indicated airspeed would drop. This scenario is similar to a headwind (upwind leg) shearing to a tailwind (downwind leg) which causes a drop in indicated airspeed.

[roundout]

[ QUOTE ]
I was under the impression that the indicated airspeed would drop. This scenario is similar to a headwind (upwind leg) shearing to a tailwind (downwind leg) which causes a drop in indicated airspeed.

[/ QUOTE ]

i think this what the original poster was referring to, now that the situation was clarified. the reason that you won't lose any IAS as you make the turn is because the turn isn't abrupt. if you make a 180* turn, it takes, what...20 seconds? more? maybe a bit less? at any rate, quite a bit of time. to get a change in IAS from shear, the change is instantaneous, hence the airplane's reaction. think back to when you had to practice S-turns and turns around a point for PPL certification.....maneuvers done with turning downwind->upwind all done at a constant airspeed. your groundspeed changes, but not your airspeed.

[carlos]

[ QUOTE ]
I was under the impression that the indicated airspeed would drop. This scenario is similar to a headwind (upwind leg) shearing to a tailwind (downwind leg) which causes a drop in indicated airspeed.

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Nope, not similar at all. Making the upwind to downwind turn, you're still in the same air mass moving at the same speed in one direction. When you encounter a shear, however, you have two airmasses moving at different airspeeds and/or directions. So you are crossing from one wind situation to a possibly drastically different one. In the first scenario, the airplane has no concept of upwind or downwind, it's just going with the flow. In the second, it's moving into a different airmass and can cause a sudden increase or decrease in performance.

[USMCmech]

[ QUOTE ]
I was under the impression that the indicated airspeed would drop. This scenario is similar to a headwind (upwind leg) shearing to a tailwind (downwind leg) which causes a drop in indicated airspeed.

[/ QUOTE ]

Nope the airspeed won't change a bit. Even durring the sharpest turn a typical GA airdraft is capable of. (Competition areobatic palnes and and F-15 fighters are the exception)


The windshear scenerio you describe does indead ocour, but it is because the wind changes direction so quickly, that the mass of the airplane get's left behind.

[kellwolf]

[ QUOTE ]
I have heard people say things to the effect that if you made a "sharp" turn from an upwind heading to a downwind heading, you could stall. Im not so sure about this theory- I thought the plane didnt care about which way the wind was blowing?

[/ QUOTE ]

Maybe if you're in a hurricane......