Take-off physics question

[BarnatosGhost]

When taking off into the wind (and I mean a STRONG wind) what happens when the wind drops?

If a plane takes off directly into a 50mph wind, at (for argument's sake) 50mph ground speed - what would happen at very low altitude if the wind suddenly dropped to 0mph? (or for arguments sake, instantly changed to a 50mph tail wind)

1) what happens to the plane's ability to climb?
2) what happen to the plane's ground and air speed?

[Dr Jekyll]

Depends on how sudden and how big (to be more precise how heavy) the aircraft is.

The aircraft will speed up to the same airspeed as before, but inertia means that this will take time. So for a while it may have too little airspeed to keep flying.

I think this is what's called wind shear.

[HRG.]

BarnatosGhost said:

When taking off into the wind (and I mean a STRONG wind) what happens when the wind drops?

If a plane takes off directly into a 50mph wind, at (for argument's sake) 50mph ground speed - what would happen at very low altitude if the wind suddenly dropped to 0mph? (or for arguments sake, instantly changed to a 50mph tail wind)

1) what happens to the plane's ability to climb?
2) what happen to the plane's ground and air speed?

Thud.

HTH.

[Quick silver]

Dr Jekyll said:

I think this is what's called wind shear.

^^^^ In a fashion, what he said.

[sherman]

Would you not just need a bigger conveyor belt.

[IforB]

BarnatosGhost said:

When taking off into the wind (and I mean a STRONG wind) what happens when the wind drops?

If a plane takes off directly into a 50mph wind, at (for argument's sake) 50mph ground speed - what would happen at very low altitude if the wind suddenly dropped to 0mph? (or for arguments sake, instantly changed to a 50mph tail wind)

1) what happens to the plane's ability to climb?
2) what happen to the plane's ground and air speed?

What you are talking about is called wind shear. The simple answer is that nothing good is going to happen to the aircraft or the people inside it. A sudden extra headwind will cause the Airspeed to increase and the amount of lift being produced will increase and with a sudden tailwind or massive decrease in headwind, then opposite will happen, you'll get a reduction in airspeed and it'll reduce the rate of climb or cause the rate of descent to increase.

Many, many crashes have been attributed to wind shear and it is especially dangerous on take off when speeds are generally lower than on approach.

Wind shear = Bad thing.

[eharding]

IforB said:

BarnatosGhost said:

When taking off into the wind (and I mean a STRONG wind) what happens when the wind drops?

If a plane takes off directly into a 50mph wind, at (for argument's sake) 50mph ground speed - what would happen at very low altitude if the wind suddenly dropped to 0mph? (or for arguments sake, instantly changed to a 50mph tail wind)

1) what happens to the plane's ability to climb?
2) what happen to the plane's ground and air speed?

What you are talking about is called wind shear. The simple answer is that nothing good is going to happen to the aircraft or the people inside it. A sudden extra headwind will cause the Airspeed to increase and the amount of lift being produced will increase and with a sudden tailwind or massive decrease in headwind, then opposite will happen, you'll get a reduction in airspeed and it'll reduce the rate of climb or cause the rate of descent to increase.

Many, many crashes have been attributed to wind shear and it is especially dangerous on take off when speeds are generally lower than on approach.

Wind shear = Bad thing.

Plockton, landing from the North, every bloody time I've been there.

Horrible. Only made up for by the best fish and chips in the world at Mister Grumpy's, as was.

Sadly, the last time round I was nursing a monumental Glenforsa hangover in the back a Maule whilst two of BA's finest in the front attempted to get us on the ground, and I was *really* looking forward to some deeply fried food. A slightly non-standard call of "Oh, bks" from the PIC, 10 feet off the runway going deeply sideways, saw us back for lunch in Oban some time later.

I got some front-seat time in the Maule later, and finally understood the problem. They might be a great STOL device, but they're ste in roll response. Not enough aileron by half.

[IforB]

Plockton can "interesting", however I reckon that the some people need to get out of their airbus' more often and into proper aircraft if they can't handle a bit of dodgy breeze! Especially with fish and chips as the prize.

[eccles]

Was at Sywell last weekend for the revival fly in. There was quite a side wind there, made for very varied approaches to getting the thing on the floor! Some looked decidedly less elegant than others.

[BarnatosGhost]

thanks for the responses.

Would it make sense then, in circumstances where wind shear could be expected, to keep the accelerating aircraft on the ground for longer than strictly necessary, in order to build up a 'buffer' of additional airspeed should the wind drop just after take-off?

[IforB]

BarnatosGhost said:

thanks for the responses.

Would it make sense then, in circumstances where wind shear could be expected, to keep the accelerating aircraft on the ground for longer than strictly necessary, in order to build up a 'buffer' of additional airspeed should the wind drop just after take-off?

Nope, you then run into other problems. As with most aircraft incidents, it's the ground/aircraft interface that is the real problem, so you want to get away from the ground asap. However, you might climb at a higher speed giving you more protection from the stall if windshear is about. Though most companies simply say to use max thrust (instead of the usual reduced thrust) and watch it like a hawk and to simply do your best to avoid windshear as much as possible and don't be scared to delay your takeoff until conditions are better. (Especially important in cases where there are microburst about causing the shear.)