Effect of wind on aircraft size
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Effect of wind on aircraft size
How does the effect of a given landing crosswind differ with aircraft size and weight? Obviously a small aircraft (C172) will be affected by the wind because of its relatively low weight but on the other hand a larger aircraft such as a commercial airliner will be affected because of its large surface area.
I guess that its not as simple as working out a weight/surface area ratio, but for a given x-wind could we speculate which aircraft will be most affected?
Given that we have many youtube examples of commercial airliners landing in very strong winds (that I guess most light aircraft would not fly in), have I effectively answered my question?
I guess that its not as simple as working out a weight/surface area ratio, but for a given x-wind could we speculate which aircraft will be most affected?
Given that we have many youtube examples of commercial airliners landing in very strong winds (that I guess most light aircraft would not fly in), have I effectively answered my question?
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In the case of light aircraft I guess extremely strong winds can cause them to shed parts, perhaps even lift them up and break them to pieces so one could say that that strong winds have the effect of reducing aircraft size.
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The most important factor is not size or weight, but stall speed. Because stall speed also determines Vref (usually somewhere between 1.2Vs and 1.33Vs) and thus how much influence the x-wind has on your approach path. A 15 knot crosswind in an aircraft with a stall speed of 45 knots/Vref 60 is a totally different matter compared to 15 knots cross in an aircraft with a stall speed of 100 knots/Vref 130.
Second factor is the size of the rudder area since that determines the amount of slip you can induce to counter the x-wind.
And then there's secondary effects. Do you have enough aileron authority to counter full rudder, do you have enough clearance under the wing (think underwing engines as on large airliners) for the bank angle you're introducing with the slip? Is maybe your undercarriage designed to withstand a certain yaw angle while landing?
Second factor is the size of the rudder area since that determines the amount of slip you can induce to counter the x-wind.
And then there's secondary effects. Do you have enough aileron authority to counter full rudder, do you have enough clearance under the wing (think underwing engines as on large airliners) for the bank angle you're introducing with the slip? Is maybe your undercarriage designed to withstand a certain yaw angle while landing?
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How does the effect of a given landing crosswind differ with aircraft size and weight? Obviously a small aircraft (C172) will be affected by the wind because of its relatively low weight but on the other hand a larger aircraft such as a commercial airliner will be affected because of its large surface area.
A changing wind (gusts, wind gradient) will have an en effect on the aeroplane in flight. A heavy airliner, for instance will be more affected by wind sheer than will a light aircraft because the big aeroplane has more inertia.
When it comes to landing in a cross wind, a faster aeroplane will be less affected because the cross wind is a smaller percentage of its airspeed (so, for instance, the angle of 'crab' on the approach will be less for a given wind in a fast aeroplane than a slow one). And the effectiveness of the flying controls, particularly the rudder, will help define the maximum crosswind an aeroplane can land in.
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Can some one please ans this
two aircrafts same approach speed lets say 120kts but different size and shape(piper senca & B737)
Which one will have more drift corection angle & y.
thks
two aircrafts same approach speed lets say 120kts but different size and shape(piper senca & B737)
Which one will have more drift corection angle & y.
thks
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If the x-wind is the same and their approach speed is the same they need the same drift correction angle, assuming they're using the "crabbed" approach (and are thus flying in balance).
When they transition to the sideslip approach it depends on a large number of design factors such as the exact fuselage shape and the size of the rudder, how much bank is needed. And with airliners the exact position of the underwing engines also become a factor. Too much bank and the engines will contact the runway.
When they transition to the sideslip approach it depends on a large number of design factors such as the exact fuselage shape and the size of the rudder, how much bank is needed. And with airliners the exact position of the underwing engines also become a factor. Too much bank and the engines will contact the runway.
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Jehan, you agree that the size/weight of the aircraft has nothing to do with the flying speed, do you? (Assuming the flying speed is above Vs and below Vne - and I agree large airplanes typically have higher values for those than small aircraft.)
So if a C172 and an airliner are both doing, say, 120 knots then they are doing 120 knots, right?
Now assume a 2-knot crosswind. If they don't correct for the crosswind they both end up two nm off-course after one hour of flight.
Over a distance of 120 nm, 2 nm offset is about 1 degree. (You can either use the 1:60 rule-of-thumb, or use arctan( 1/60 ) ). So to correct this offset, they both need to steer into the wind by 1 degree.
Again, all completely regardless of weight or size.
And if you don't fancy complex (...) calculations, consider this. There's a rubber bathtub duck and an oil tanker floating around on the North Sea. Both are using no engine power whatsoever, and we are also disregarding wind. Both will then drift with the tide. Making the same speed over the ground, regardless of their size or weight. Same thing.
So if a C172 and an airliner are both doing, say, 120 knots then they are doing 120 knots, right?
Now assume a 2-knot crosswind. If they don't correct for the crosswind they both end up two nm off-course after one hour of flight.
Over a distance of 120 nm, 2 nm offset is about 1 degree. (You can either use the 1:60 rule-of-thumb, or use arctan( 1/60 ) ). So to correct this offset, they both need to steer into the wind by 1 degree.
Again, all completely regardless of weight or size.
And if you don't fancy complex (...) calculations, consider this. There's a rubber bathtub duck and an oil tanker floating around on the North Sea. Both are using no engine power whatsoever, and we are also disregarding wind. Both will then drift with the tide. Making the same speed over the ground, regardless of their size or weight. Same thing.
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Guys i apologize for for using text speech.
From the above post i get it that we don't use aircraft size/ weight in consideration for calculating drift or wca.
But for instance if there are 2 bodies different size but moving in same direcion SAME velocity and if you apply force from the side the one which has large momentum(due to its weight)will get deflected from its path less than the one one with small momentum(due to less weight). If this is the case then why cant we apply it to our aircraft.
Please give your input.
Thanks.
From the above post i get it that we don't use aircraft size/ weight in consideration for calculating drift or wca.
But for instance if there are 2 bodies different size but moving in same direcion SAME velocity and if you apply force from the side the one which has large momentum(due to its weight)will get deflected from its path less than the one one with small momentum(due to less weight). If this is the case then why cant we apply it to our aircraft.
Please give your input.
Thanks.
Last edited by jehan; 6th Dec 2012 at 06:53.
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But for instance if there are 2 bodies different size but moving in same direcion SAME velocity and if you apply force from the side the one which has large momentum(due to its weight)will get deflected from its path less than the one one with small momentum(due to less weight). If this is the case then why cant we apply it to our aircraft.
Also to be considered is the 'shape' of the aircraft... a large tail could cause the plane to 'point' into the wind, a large front end could cause it to point away from the wind, an airplane with the nose wheel on the ground will be less likely to point into the wind than one with the nose off the ground or a tailwheel airplane... a high-lift wing could cause the plane to be affected more than a low-lift/high-speed wing
So yes, you are right, to a degree, however the shape of the plane, wing, and tail, wheel configuration, position at the time, speed, variance of the wind, and many other factors have effect on how much a crosswind will affect an aircraft. These other factors generally have greater effect than mass (weight) and size.
Generally, a 'big' airplane (think A380 or 747) will be less affected than a 'small' airplane (think Cessna 152), however to give an example where shape is more of a factor, think of the space shuttle versus an A380. The space shuttle has almost no lift compared to the A380, and thus the A380 is more affected by cross wind than the space shuttle, but the space shuttle is about 1/4th the size and mass (weight) of an A380.
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darkroom - not sure what you're saying there. Any steady wind (cross or not) has absolutely no effect on any aeroplane, from a glider to an A380 to a Space Shuttle, other than to vary its groundspeed and track. It has absolutely no effect on how it flies.
Regarding aligning with a runway which has a crosswind, this means a certain amount of sideslip has to introduced, usually yaw with the rudder to get onto the runway heading, with appropriate aileron to prevent a turn.
As I said before, the differnece between track and heading in a crabbed (flying in balance) cross wind approach depends only on speed. The slower the aeroplane, the greater the difference. Hence a Space Shuttle is far less affected than an A380 because the approach speed of the Shuttle is much greater than that of the 380.
The shape of the aeroplane has absolutely no effect at all in the air regarding differentt winds. Don't forget, to an aeroplane in the air THERE IS NO WIND! Wind is simply the air mass moving relative to the ground, and the aeroplane (or balloon!) is suspended in that air mass and so moves with it.
Regarding aligning with a runway which has a crosswind, this means a certain amount of sideslip has to introduced, usually yaw with the rudder to get onto the runway heading, with appropriate aileron to prevent a turn.
As I said before, the differnece between track and heading in a crabbed (flying in balance) cross wind approach depends only on speed. The slower the aeroplane, the greater the difference. Hence a Space Shuttle is far less affected than an A380 because the approach speed of the Shuttle is much greater than that of the 380.
The shape of the aeroplane has absolutely no effect at all in the air regarding differentt winds. Don't forget, to an aeroplane in the air THERE IS NO WIND! Wind is simply the air mass moving relative to the ground, and the aeroplane (or balloon!) is suspended in that air mass and so moves with it.
darkroomsource
The only time that an aeroplane can experience weather-cocking effects is when it's on the ground.
That's because when on the ground the wheels act as a pivot-point about which the aeroplane can rotate. The rotating moment is caused by a difference in the total wind load on the fuselage in front of and behind the pivot point.
This simply cannot happen in the air.
FBW
The only time that an aeroplane can experience weather-cocking effects is when it's on the ground.
That's because when on the ground the wheels act as a pivot-point about which the aeroplane can rotate. The rotating moment is caused by a difference in the total wind load on the fuselage in front of and behind the pivot point.
This simply cannot happen in the air.
FBW