Cross winds on FSX flying

[volunteer]

I can understand why a plane should weathercock into the wind on the ground. But why doesn't it do it when its flying  -  wouldn't the cross wind hit the tail more than the front causing the plane to slowly weathercock?
How do you stop this- is it
rudder or ailerons?
So if I point to a target in a cross wind - I will wind up downwind of the target unless I compensate for the wind - just like you do when yachting with tides  -is this correct?
confused!
thanks
volunteer

[pepper_airborne]

Im not quite sure what you are talking about, but yes, a wind will definately offset your plane, trying flying too a random VOR at a heading of 360, then setting a 90 degree crosswind, you will notice you need too point your plane slightly into the wind for compensating for the offset.

[BFMF]

[quote]wouldn't the cross wind hit the tail more than the front causing the plane to slowly weathercock?
How do you stop this- is it
rudder or ailerons?
So if I point to a target in a cross wind - I will wind up downwind of the target unless I compensate for the wind - just like you do when yachting with tides

[Splinter562]

One of my PPL manuals had an illustration of a boat crossing the river. If it didn't point upriver to compensate for the current, it would end up downriver from it's objective, or If the boat crossed the river with the objective always kept at the 12 O' clock position, it's course ended up being a big arc.

Correct. Think of the wind as the entire atmosphere moving sideways along the surface of the earth. If you are on the ground, you feel the atmosphere moving by you as wind. But, if you are in the air, you simply move with the atmosphere as it slides across the ground. Discounting instabilities in the atmosphere (gusts, wind shear, thermals, etc.), the airplane flys exactly the same in calm winds as it does in a 50 mph wind because it is moving with the airmass.

The path that you are taking through the airmass is defined by heading (where the nose of the airplane is pointing) and true airspeed. If the airmass is moving in relation to the surface of the earth ("wind"), then you are traveling with it. As I pointed out before, this doesn't change the way the plane flys, but what it does is changes the path it is taking along the ground. If you were to make an arrow showing your path through the airmass (heading & TAS) and add to it an arrow showing the movement of the airmass across the ground (wind) then the resulting arrow would give you the airplane's actual path over the ground. If you've ever used a manual E6B this is exactly what you are doing when you use the wind face. The direction of your path along the ground is your track and the speed at which you move along the ground is your ground speed.

So, if you are flying with a 20 knot tailwind, the aircraft would handle exactly the same as it would in calm winds, but your ground speed would be 20 knots faster than your true airspeed.

If you are flying with a 20 knot cross wind from left to right, the aircraft would handle exactly the same, but your track would be a few degrees to the right of its heading.

The challenge comes when you have to take the airplane which is moving with the airmass, and land it on a runway which is not. You can see now the reason pilot's always try to land into the wind. If you touch down at 55 knots true airspeed into a 10 knot headwind, then the aircraft is actually only moving forward at 45 knots in relation to the runway. And the tricky part is if you have a 10 knot crosswind, then the plane is trying to move sideways in relation to the runway at 10 knots. One of the harder parts of getting your pilot certificate is to learn how to  deal with crosswind landings.

[Brett_Henderson]

This is a good thread. We touched on this stuff in the Sim Flight Training, as it applies to flight planning... but never got into the nitty-gritty. It's also an opportunity to point out the differences between; heading, course, track, bearing and relative bearing.

The best way to demonstrate how wind affects a plane in flight; is with vectors..



You math whizes can do the geometry.. but this shows it pretty well..

[beaky]

The "weathercocking" on the ground is due to the main wheels providing a pivot point.
The aft part of the fuselage is like a lever, the mains are the fulcrum, and the wind is the hand pushing on the lever.

As Splinter points out, a plane in the air is not being "hit" by wind all- it's moving with the wind, even if it's not going in the same direction.
Think of a goldfish swimming in a bowl which is being carried. He might note his sideways track relative to the ground he can see below his bowl, and if he's swimming opposite the direction his bowl is being carried he will see he's moving slower along the ground,but his other senses notice only the flow of water along his nose.

So what we call "wind" is really just the effect of being hit by that moving mass of air when we are in contact with the ground... a hot air balloon's occupants might have to hold onto their hats in a strong breeze before launch, but as soon as the wind is allowed to carry the balloon away, they could light a candle up there and it will stay lit, even in high winds... there's no perception of wind when you are drifting with the moving air.

An airplane might get pushed a bit briefly if it enters a region where the wind is flowing differently, but it passes quickly.

Also, bear in mind that MSFS does a bad job modeling the effects of wind on planes on the ground- for example, in FS9 tricycle-gear planes often weathercock, but this is really not the case in real life, as the CG of the plane is forward of the mains. Part of the reason nosewheels were first put on planes, as taildraggers will definitely weathercock.

EDIT:
It's been brought to my attention (by a pilot with quite a bit more flight hours than myself) that real-life trikes do, in fact, try to nose into the wind sometimes while rolling on the runway, so I'd like to add the following:


I guess I often say "trikes don't need rudder for wind on the roll" or words to that effect because I don't really think about it in RL, whereas in MSFS, it's ridiculous sometimes.
I guess I should have said "appreciably"...

I'm trying to recall a specific occasion where I consciously added some "downwind foot" while rolling a trike in RL... hmmm... I guess I've made most of my xwind takeoffs with the wind off the right quarter or something, because I'm hard-pressed to recall using much rudder for anything except  the usual full-power prop effects (which tend to pull the nose to the left with the vast majority of small piston engines).

I do actually remember a couple of times where I needed some rudder in addition to aileron on the landing rollout... but that's probably due more to the nosewheel not being fully loaded yet.  It's easy in a C-150 or something to touch down straight, only to start veering into the wind because you have that full aileron into the wind but not enough nosewheel and/or rudder deflection to stay on the centerline. The lighter the trike, the more you have to "fly the rudder" as the landing continues into the roll (in a crosswind).

I suppose the same applies to the takeoff roll- once the nosewheel comes up, there's that much less resistance to the leverage of the aft fuselage. but again, I guess I usually don't think about what my feet are doing- I just work my feet to keep the nose centered, and in trikes, it doesn't take much, usually.



Taildraggers, on the other hand, definitely are more prone to weathervaning because of the CG thing... there's more mass behind that pivot point than in front of it, and no nosewheel friction to combat the effect.
 But it's not usually a big deal... except for that moment, whether taking off or landing, when you are transitioning between tailwheel steering and rudder steering. A novice like myself still has trouble picking just the right moment to either raise or lower the tail, especially during a wheel landing.

[volunteer]

Oh - I see - so thank you all for helping with that.

But there is another point on this. You are flying along in your Cessna (like I do) - I don't know what the state of the wind truly is. I can see the thing (a mountain for example) the planes nose is pointing at and it is moving to the left - so I guess the wind is coming from the right. How do I compensate for that? Is there any rule of thumb?

Is it all rudder ? Or do you also apply aileron?

So I come into land - with my cross wind going
is it better to have it on the left
or shall I change direction so the cross wind is coming from my right?
Or do I simply aim up wind if I can?
thanks for all your time
(Oh - I would never fly for real - its all FSX which rocks in my view)
volunteer.

In FSX you can take any plane out in any wind. But in REAL world flying there must be rules for wind speed and safety - especially in little planes. So I could also ask - when is a flying day realy a no-flying day please?

e6600 in Asus P5N E SLI overclocked to 3250 with standard cooler. 3 G memory

[Brett_Henderson]

Oh - I see - so thank you all for helping with that.

But there is another point on this. You are flying along in your Cessna (like I do) - I don't know what the state of the wind truly is. I can see the thing (a mountain for example) the planes nose is pointing at and it is moving to the left - so I guess the wind is coming from the right. How do I compensate for that? Is there any rule of thumb?

Is it all rudder ? Or do you also apply aileron?

So I come into land - with my cross wind going
is it better to have it on the left
or shall I change direction so the cross wind is coming from my right?
Or do I simply aim up wind if I can?
thanks for all your time
(Oh - I would never fly for real - its all FSX which rocks in my view)
volunteer.

In FSX you can take any plane out in any wind. But in REAL world flying there must be rules for wind speed and safety - especially in little planes. So I could also ask - when is a flying day realy a no-flying day please?

I'll address this as though it were real flying. It's that state of mind that makes MSF such a valuable training aid, and makes it so much fun..

You kind of answered you first question when asking it. If you see something out on the horizon, and can sense that you're moving laterally.. you simply change your heading so that it becomes a stationary target. This is especially handy when departing... it can keep you from drifting off runway center-line..

As for correcting for the wind in flight.. you just fly a heading that compensates for the wind. Go check out the 'Sim Flight Training' in this section of the forum. We discussed it in depth.. especially the flight planning aspects. Trying to hold an aileron or rudder correction will just keep you in a constant turn.. when all you want to do is fly the adjusted heading.

Landing in a cross-wind is the first, serious challenge a new pilot faces. Wind from the right or left doesn't matter (and since all planes should be using the same runway, so they don't

[beaky]

Just a note from the Peanut Gallery:
To "stationary target", when referring to a point on the horizon, I would add "not necessarily what the nose is pointed at".
 Unless the wind is aligned precisely with your course, your target ain't gonna be dead ahead. But you should be able to fly towards it without knowing exactly the wind's heading simply by observing it.
If, for example, that tower on a hill that is your visual waypoint is, say, directly above the clock on the panel, all you have to do is make it stay there, not make it move to the center.  Once you get really close, of course, it will move across your field of vision, but for general purposes the idea is to keep it "still" as long as possible.



With a little practice, it's easy to "crab" towards something pretty accurately, once you get used to how that looks in your field of vision.
Best way to practice that in MSFS is to create a good strong wind across your course- the greater the angle, the better.

[Splinter562]

To tack on to what Brett has already said, the Maximum Demonstrated Crosswind is required by regulation (FAR 23.1585.a.2) to be defined for small aircraft (normal, utility, aerobatic, and commuter catagory). For the Cessna 172 it is usually 15 knots. BUT the important thing to note is that this value is not a limitation like red-line on the airspeed indicator, it is an operating procedure. It falls into the same category as the yellow-arc on the airspeed indicator. It is recommended that you fly below the yellow-arc in turbulent air, but not required. Same thing here, it is recommended that you not land with a faster crosswind than the maximum demonstrated, but not required. This is why it is perfectly legal for Brett to land in a 25 knot crosswind in a 172. That being said, if you were not highly experienced in crosswind landings and had an accident, the FAA would fault you as the pilot for operating outside of the manufacturer's recommendations. Now, if you are renting from a flight school, they may have their own limitations on crosswinds (and often do) so that you would be violating the flight school's rules if you landed above those values.

[Brett_Henderson]

Be sure, I don't advocate landing in crosswinds greater than a plane's published, demonstrated maximun.. But if that wind is the product of much nastier than forecast weather for a destination... it's better to land than to brave the weather. Your inexperience with crosswind landings will probably be better tested, than testing your inexperience flying and navigating in a sudden storm..

[volunteer]

thank you again

I will go and practice all this and report back!
thanks fellows
volunteer

[OTTOL]

Just my $.02.....

To be fair to the guy; FS does not accurately depict crosswind dynamics.

I stopped adding any kind of strong winds a long time ago because it was too frustrating trying to land and takeoff with the aircraft wanting depart the runway regardless of rudder input.

On real aircraft (even as an IP of experienced turbine pilots) my number one maxim is "fly the aircraft as long as it's moving."  I can't tell you the number of "seasoned" pilots that I have seen rolling down the runway at 100kts+ with a wing dipping solidly into the wind! Once there is air flowing over the aircraft you have to start making control inputs.

On real aircraft, it's as simple as this:

Use Ailerons-to keep the wings level.

Use Rudder-to maintain centerline.

Like I said, it's been awhile since I've flown the sim with wind but I seem to remember being able to maintain centerline only with large aileron inputs.  

Once you're airborne the scenario changes a little bit. If you rotate with this control combination in a crosswind, you'll be slipping. You just transition, smoothly, to normal inputs when the wheels clear the ground. It's essentially a reverse engineered landing.

.....okay, maybe that was $.20...

[Brett_Henderson]

Hmmm.. I've found that MSFS (especially FSX), does a pretty good job of representing crosswinds... both on the ground and in the air. Are you using yoke & pedals, or a twisting joystick ?

[OTTOL]

Firstly, the second paragraph of your last response is spot-on. Nice work!

I haven't got a copy of FSX yet (no matter how much money I make I'm still a cheap-arse.....that's good financial operating advice to anyone on the rise to success BTW!)
I have a "twist" type joystick and, in the interest of partiality, I understand that the degree of precision with which you can make control inputs relies on the quality of the hardware.
With any control system though, if you have full rudder deflection in and still can't maintain runway centerline (in medium intensity winds), that is a programming flaw!