Crosswind effect
 

I have often read that large aircraft side area increases the effect of a crosswind.
My belief is that once inertia is overcome, and the plane is flying in a steady state, it makes no difference how much side area or wing loading a plane has. It is flying in a "sea of air" and crosswind is only relative to the ground.
The amount of "drift" will be the same for all shapes.
True or false?
Thanks!
JLK

RE: Crosswind effect
 

Even though it may be flying in a sea of air there still is a crosswind,headwind, or tailwind or any combination . Going from point A to B requires a track over the ground and the wind will determine the heading that will be required to maintain that track. The heading required will be different for different shapes ,sizes and speeds of the airplane. A Piper Cub would be affected more than a 747.

RE: Crosswind effect
 

That's not my point.
What I am referring to is the belief that the amount of that correction is determined by the side area and differs accordingly.
JLK

RE: Crosswind effect
 

That crappola is gospel to some pattern guys --who really believe that the new wide body pattern models drift more in the wind .
Having carefully explained that the corrections the flyer performs--plus the slower speed is the culprit - I still get "maybe so" answers .
The huge side area aft the CG does make some of those pigs harder to herd in slow maneuvers -in wind--but that is because they are so overstabilized in yaw. Back when w did our EMC 2 the side aread was large -but much of it was forwad the CG- to make slow flying easier (only enough yaw control to do the job)
anyway -I got sick of all that Bull s hit.

RE: Crosswind effect
 

Right'O Dick!

You are right jlkonn. However one must be careful to define conditions, because side area distribution relative to the landing gear become important during takeoff and landing, while the wheels are on the ground.

But in the air, it doesn't matter whether it is a 747 or a Piper Cub, the only things that affect crab angle are the aircraft's true airspeed and direction, and wind speed and direction. Size of the airplane doesn't matter at all, nor does side area. If a 747 and a Cub were able to fly at the same speed (which of course they can't) in the same wind, they would have the same crab angle. Or a Piper Cub and the Goodyear Blimp. You get the idea.

RE: Crosswind effect
 

You're right jlkonn, for a STEADY STATE the model sees only a head on wind and it's only the visual effect of an observer on the ground that sees it drifing.

But if it's flying in turbulent conditions then the side area will come into play for the duration of any side angular wind effects until the model is once again flying head on into the air. But that is a very transient effect and if the air is enough of a washing machine that it's a significant time % then the pilot will be far more likely to be at home typing on the internet.... :D

RE: Crosswind effect
 

Bruce,
With all due respect.
Your comment "once again flying head on into the air" illustrates what I feel is the misconception regarding crosswind. The effect is only relative to the ground. The airplane, unless it is being flown in uncoordinated flight such as a slip, is always flying "head on into the air". The "crab" is only seen by an observer on the ground.
What caused me to bring this all up was a remark on a pattern thread about a plane with a particularly large amount of side area not being a successful design when flown in a crosswind.
In a steady state I don't agree.
JLK

RE: Crosswind effect
 

Heading (distance towards or away from the viewer) is important in pattern.. a crosswind would require slipping to hold the heading line. Some can do it, others can't.. It's like vertical manuvers in a strong wind.. the line is important, not the attitude.

RE: Crosswind effect
 

jlkonn, we're on the same wavelength. But I was just introducing the aspect of response to the turbulence in the air.

The air our models fly in is often full of wind direction shifts due to thermals or trees. Other than on calm days our models are constantly being hit by and responding to side and vertical air movements that the model will see as cross winds or side slips or sudden changes in the apparent angle of attack. And the models respond to these localized changes in wind direction or velocity by tipping a wing, dropping a nose and a host of other effects. But a stable model will adapt to this short term disturbance quickly and "once again be flying head on into the air" :D

Sailplane fliers depend on this effect as it's the only real method we have for seeing what the air is doing and how to best respond to what we hope is a thermal. Power models see this sort of air turbulence as annoying but the models still respond to it. The ones with the larger side areas are obviously going to respond to it with a little more verve than something skinny.

RE: Crosswind effect
 

I am amazed that people think that there is something different about flying in a crosswind. The airplane doesn't know anything about which way the wind is blowing, and doesn't care, unless its wheels are touching ground. A full-scale pilot actually told me that when flying in a crosswind, he dials in a bit of crossed rudder and aileron trim in order to point the nose closer to his destination, and flies with the ball well off-center. I told him all he will accomplish is slowing his airspeed and his average speed over the ground, but he was far from convinced. I guess old habits and misconceptions die hard.

RE: Crosswind effect
 

Most of the stuff on the pattern page is relative to how much work the flier does in order to hold a line.
So the larger model - - -if flown slower - really becomes a handful as wind drift carries it and the apparant fuselage angle required is very visible.
been there - a million times
The optical illusion is that the big fuselage is being blown sideways
Flying little foamies ( those things again) cut into various relative sizes shows this easily.
The only fix is speed -speed and then speed.

RE: Crosswind effect
 

ermm... Is that what you really meant to write? Are you sure you didn't mean crab, instead of slip?

RE: Crosswind effect
 

I never would have signed off a student who said something like that to me. He would have gone into remedial training, or gotten himself a different instructor.

RE: Crosswind effect
 

Horizontal slip. :)

RE: Crosswind effect
 

Would you please explain that? Why would you slip to correct for a crosswind, unless it was a sideslip to align the gear for touchdown?

RE: Crosswind effect
 

No. Chase your own tail

RE: Crosswind effect
 

I already know the answer. Apparently you don't. No tail chasing involved.

RE: Crosswind effect
 

If you applied your method to full scale flying you will end up in places that will not be to your liking. Why do I say this? since the mid 60s I have held comercial SEL MEL and CFI tickets. And as another fellow on here said I certainly would never sign off anyone that thought that way.
If we are talking Xwind as applied to landings then wind gradients are also a factor. Many a otherwise good landing has gone bad because the pilot did not carry a little extra airspeed on final to compensate for localised wind speed variations. It gets to be more fun at night when the visual cues are practically non existent.

RE: Crosswind effect
 

Well said, Gremlin Castle, from a retired ATP.

feihu