As I said: Using the shuttle I was attempting to clarify for the OP that even though mass (weight) has SOME effect, it is minimal. Using a rock and an aeroplane would be a better example. A paper aeroplane weight less than a rock. A paper aeroplane will be blown about in windy conditions, a rock will not (Unless it's REALLY windy), BUT a Cessna 172 which is much heavier than the same rock will also be blown about more than the rock in windy conditions. So weight (mass) is NOT a major factor in the effects of wind, cross wind, gusts, turbulence or any other changes in air flow. Shape is far more important.

However momentum (which is affected by weight/mass and speed) does have some affect on the effects of other forces being applied to an object, whether those forces are gravity, propulsion, or wind. It is just that in the case of something designed to fly, the shape has more influence on the effects of wind than does the mass of the object.


@Fly-by-wife, I beg to differ, weather cocking can be seen and felt in flight. It will be about EITHER the point with greatest resistance (as in the wheels when on the ground, or a pivot point in a wind tunnel) OR it will be about the centre of gravity in flight. This is what we experience in turbulent air when the plane pitches or yaws. It is that some parts of the plane will present more drag than others, and thus be affected more - BUT it is absolutely NOT related to weight (mass) or over-all size of the aircraft.

FBW, I don't entirely agree. An aircraft has mass, and thus momentum, and the center of gravity (around which it will pivot) might not be the same as the aerodynamic center on which a cross-gust might act.

In fact, the fin is designed to have a large aerodynamic cross-section to any crosswind, a small aerodynamic cross-section to any headwind, and to sit well behind the center of gravity. So it acts as a weather-vane, weather-cocking the aircraft into the relative wind and thereby removing any sideslip. Whether that sideslip is induced by the pilot or caused by a gust of wind is irrelevant.

And if the aircraft yaws because of a gust of wind, I would call that weather-cocking, even in flight.

I don't think it's a *better* example. In fact, I find the example worse.

A rock and a paper aeroplane on the ground will be blown about, or not, because the forces exerted by the wind are higher than the friction between the object and the ground, or not. The rock is denser so will experience less aerodynamic force and more friction, so it takes a higher wind to blow it about.

And a rock and a paper aeroplane that are free-falling will be blown about by the wind equally. However, it takes a while before the wind has overcome their momentum fully, and before that happens the rock will be on the ground. So it might appear that a rock will fall straight down, even in the wind, but that's just because it takes a while for the wind to "catch" it.

And that momentum is the key. Assuming steady conditions (non-gusting x-winds for instance), the weight, size and shape of the aircraft don't matter one bit. But if you assume non-steady (gusting) conditions, it becomes a matter of the actual weight of the aircraft and it's size. Or better yet, it's aerodynamic shape as seen from various angles.

A rock isn't an aeroplane. It isn't flying suspended in the air mass as the paper dart is, it's falling through it. Comparison invalid.

If you want to demonstrate that a steady wind has no effect on a flying machine other than to affect track and ground speed, a hot air balloon, an A380, and Concorde would be good examples to use.

so to summaries the weight and size does effect the but it is very small and so can be neglected as the main factors are aircraft speed ,wind speed & wind direction and also shape of the aircraft.

Is that rite.
Thanks.

No, that is not 'rite' (sic).

I don't know how many times I have to say this....

Oh, never mind. If you didn't read it the last 'n' times I wrote it you won't read it if I write it again.

Just go back and read my posts. It really could not be put more simply than I already have.

If I may say so, this thread has become silly.

There is a lot of bumph here, but not all of it is.

LM (ex-RAF QFI)

Lighting mate @
 

Lighting mate @ sir can you please provide us with right information on the mentioned topic.

thanks

LM has alluded in his post that the correct information has already been given in the thread. Along with a lot of dross.

I agree, it's now got silly.

Shaggy Sheep Driver already has.

I don't have the time.

But Shaggy is ONLY talking about "steady wind"
I have yet to land in a "steady wind", ever.

Taking the discussion away from steady wind conditions and wind gradient, I imagine gusts feel worse in a light a/c - which is all I fly - and they react rather quickly by change of height or trying to move off line on short finals, especially with trees around.

However a massy plane will have substantial inertia and during the landing phase if/when hit by a gust would surely be unlikely to change its attitude, unless the new wind direction is sustained. Thus it would continue as directed because a short burst of wind energy relatively is not very significant.

On reflection even landing a very light a/c demonstrates this effect.

Landing the Rans S6 into a strong wind through the gap in the trees at my base strip, she always suffers short sharp turbulences and wind direction changes caused by it tumbling through & around the trees etc. Thus mostly I've found it best - whilst very prepared to pedal etc.,- to hold my controls as she'll emerge a few lengths later on the same path and skew for the last phase immediately before round out the same as she started with just before.

Hope that practical attempt helps the conundrum.

MikeH

Yes.

On a practical note it is always revealing when you watch a pilot new to twins fly a twin for the first time.

Consider perhaps a 20 knot gusting cross wind and in most if not all singles the pilot will be working reasonably hard (some more than others ;)). Now fly the same approach in one of the more substantial twins (perhaps and Aztec is as good an example as any) and you instantly wonder what all the fuss is about - it just becomes a complete non event.

The difference is quite surprising at first, even if the approach is not nearly as much fun.

Of course aerodynamically there is a great deal more going on than the aircraft changing from any old light single to any old heavy twin but most pilots are interested in how in looks and feels rather than the physics.

Mike,
As you've noted as you land when the wind changes direction or speed the aircraft feels the effects of changes in forces on its surfaces.
A heavy aircraft will have momentum in its favour, obviously, however and if you have the same aircraft landing with different weights, you'll see a SMALL difference between the two loadings.
However if you have two aircraft with the exact same weight, but one of them has a tail surface that is 4 times the size of the other, you will see a DRASTIC difference between the two aircraft.
Mass (weight) DOES have an effect on the affects of wind, however shape has a much greater effect.

As one nears the ground on a crosswind approach and the 'steady' wind is augmented by coriolis effect, wind shear, wind gradient, and ground-feature-induced gusts, and mass becomes a factor.

A big, heavy aeroplane will be more affected by wind gradient and wind shear, less by gusts. A light aeroplane will be less affected by wind gradient and shear (but will still be affected to some degree), and more affected by gusts.

The shape of the aeroplane makes not the slightest difference on the approach and landing until it's no longer flying and it becomes a non-flying object sitting on the ground.

Tell that to NASA and every Aeronautical Engineer in the world, because they obviously don't need to worry about the shape of a wing, and all the time they've put into wing technology has been for naught.

darkroom - you have (I suspect deliberately) taken part of my quote out of context.

We're talking about the effect of wind here. If the aeroplane arrived on the ground it fulfilled the requirements for flight while it was landing. Once tied down and the aeroplane becomes a 'land object', different rules apply. Which as I know you know was what I was referring to.

Oh for fcucks sake you ill-informed twats!!!!!!!!!

guys nobody out here is actually answering my question.

My question was "Why is aircrafts momentum, size and shape not taken in consideration while determining drift angle"

can some one please give me a simple explanation.

Thanks.

Imagine sitting on the ground watching a large weightlesss box of still air blowing in the wind. The only thing which affects the movement of the box is the speed of the wind.

Now imagine being in the box watching an airplane flying inside it. Since the air inside the box is still, the only thing which affects the movement of the airplane in the box is the speed of the aircraft.

Put the two together, and hopefully you will see that the only variables which affect the motion of the airplane relative to the ground are the speed of the wind and the speed of the aircraft.