Crosswind Landings - Crab or side slip??
06-15-2006, 08:07 AM
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Crosswind Landings - Crab or side slip??
Hi,
I am a student pilot. I've had about 10 takeoffs & landings so far in dead calm days. Last night I went flying in about 10-12 miles crosswind. I could not land a single time because plane will get drifted over runway & last time I went & hit nets in pit area.
I have not been using rudder so far for any of my flight because I am using LT-40. I have training with several instructors & never realized importance of learning to use rudder until yesterday. I knew that I have to learn to use rudder someday but was thinking I can solo first & learn to use rudder at my own time. I did not want to extend my solo any more than necessary.
Now I have determined to use rudder even if it means few more flights before solo. Can somebody please explain if I should crab or slip in crosswind conditions & how to do that. I generally understand that you crab into the wind but I assume because of dihedral on the wings, plane will actuall start turning.
Any help will be greatly appreciated....
Regards,
Sujit Chokshi
I am a student pilot. I've had about 10 takeoffs & landings so far in dead calm days. Last night I went flying in about 10-12 miles crosswind. I could not land a single time because plane will get drifted over runway & last time I went & hit nets in pit area.
I have not been using rudder so far for any of my flight because I am using LT-40. I have training with several instructors & never realized importance of learning to use rudder until yesterday. I knew that I have to learn to use rudder someday but was thinking I can solo first & learn to use rudder at my own time. I did not want to extend my solo any more than necessary.
Now I have determined to use rudder even if it means few more flights before solo. Can somebody please explain if I should crab or slip in crosswind conditions & how to do that. I generally understand that you crab into the wind but I assume because of dihedral on the wings, plane will actuall start turning.
Any help will be greatly appreciated....
Regards,
Sujit Chokshi
06-15-2006, 08:54 AM
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RE: Crosswind Landings - Crab or side slip??
Practice in the air at least 2 mistakes high. Just practice adding rudder slowly and using the ailerons to keep the wings level. With the dihedral wing in a cross wind, you will actually want to keep the upwind wing slightly below the downwind wing. This will help fight the tendency of the wing to be picked up by the cross wind. Practice doing this with the plane in an approach direction. This is whats known as flying a wind corrected line.
Also, when dealing with cross wind, you'll need to use more speed on approach. Beginners like to make slow approaches and chop the throttle to drop onto the runway. This makes handling cross wind harder. Trim your plane such that the nose will drop slightly as you drop the throttle to help fight the tendency of the trainer to balloon on approach. Then "fly the plane" down to the runway. As you get used to that, it makes it easier to handle a faster landing that you need to deal with cross winds. I like to help my students understand that landing is no different than flying, its just a question of altitude.
Brad
Also, when dealing with cross wind, you'll need to use more speed on approach. Beginners like to make slow approaches and chop the throttle to drop onto the runway. This makes handling cross wind harder. Trim your plane such that the nose will drop slightly as you drop the throttle to help fight the tendency of the trainer to balloon on approach. Then "fly the plane" down to the runway. As you get used to that, it makes it easier to handle a faster landing that you need to deal with cross winds. I like to help my students understand that landing is no different than flying, its just a question of altitude.
Brad
06-15-2006, 09:18 AM
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RE: Crosswind Landings - Crab or side slip??
Sujit,
Here is a good drill to practice using your rudder for landings: Line up for final like you would usually do for a landing, but keep the power up to about half throttle, and only descend to about 50 feet above the runway. Fly down the center of the runway at an altitude of about 50 feet and do the following: Using your ailerons, just keep the wings level; don't bank the plane too much at all. Now with the rudder, controll the path of the plane as it goes down the center of the runway. If you drift to the side at all, use your rudder to steer the plane back to the centerline of the runway. As you do this, keep the wings level with your ailerons. Once you clear the runway, increase power and climb, and use your rudder to keep the plane centered on an imaginary line drawn out from the center of the runway, until you have full power, and you are ready to turn.
Once you find it easy at that power setting and at that altitude, try it a little lower and slower, until you are landing the plane using that technique. If you do this right, you will learn to use the rudder and coordinate it's use with your ailerons while taking off and landing, and your landings will be much smoother and consistant. It's just a matter of practicing it over the runway at a safe altitude, over and over again until you get it. Good luck!
Here is a good drill to practice using your rudder for landings: Line up for final like you would usually do for a landing, but keep the power up to about half throttle, and only descend to about 50 feet above the runway. Fly down the center of the runway at an altitude of about 50 feet and do the following: Using your ailerons, just keep the wings level; don't bank the plane too much at all. Now with the rudder, controll the path of the plane as it goes down the center of the runway. If you drift to the side at all, use your rudder to steer the plane back to the centerline of the runway. As you do this, keep the wings level with your ailerons. Once you clear the runway, increase power and climb, and use your rudder to keep the plane centered on an imaginary line drawn out from the center of the runway, until you have full power, and you are ready to turn.
Once you find it easy at that power setting and at that altitude, try it a little lower and slower, until you are landing the plane using that technique. If you do this right, you will learn to use the rudder and coordinate it's use with your ailerons while taking off and landing, and your landings will be much smoother and consistant. It's just a matter of practicing it over the runway at a safe altitude, over and over again until you get it. Good luck!
06-15-2006, 10:16 AM
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RE: Crosswind Landings - Crab or side slip??
For cross wind landing. the side slip is helpful. To do this, on final, bank the wing into the cross wind i.e., if landing with a wind from the left, bank left, just enough to counter the tendency to "drift" to the right. Also apply right rudder, a little bit, otherwise the plane will weathervane to the left, into the wind. So, the combination of left bank (into the cross wind) and right rudder will have the plane banking left while still pointing straight down the runway. This maneuver bleeds off altitude as well, be sure to keep your power up enough to maintain adequate speed.
Do this several times at altitude to help you get the feel of how much control input is needed to keep the plane on track over the runway with the cross wind. I think you will find it is fun to do.
Do this several times at altitude to help you get the feel of how much control input is needed to keep the plane on track over the runway with the cross wind. I think you will find it is fun to do.
06-15-2006, 11:20 AM
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RE: Crosswind Landings - Crab or side slip??
I side slip in cross winds.
The hard thing I find for students is then have a hard time dealing with the angled attack on the runway. I try to let the model do what it want to when coming in. On appoch lined up with the runway. Them let go for a second and touch the rudder into the wind maintaining about 1/3 throttle. Let the model weathervein into the wind, the plane will point off to one side into the wind and it's flightpath will be right down the runway. trainers seem to just naturally side slip. balance the throttle and runnder to keep it in the center of the runway using ailerons to keep the wings level. at about 1 foot off the ground. touch the rudder the other way to set it straight down the runway
The hard thing I find for students is then have a hard time dealing with the angled attack on the runway. I try to let the model do what it want to when coming in. On appoch lined up with the runway. Them let go for a second and touch the rudder into the wind maintaining about 1/3 throttle. Let the model weathervein into the wind, the plane will point off to one side into the wind and it's flightpath will be right down the runway. trainers seem to just naturally side slip. balance the throttle and runnder to keep it in the center of the runway using ailerons to keep the wings level. at about 1 foot off the ground. touch the rudder the other way to set it straight down the runway
06-15-2006, 11:46 AM
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RE: Crosswind Landings - Crab or side slip??
OK, we have a bunch of ideas that are not well explained.
1) A "crab" is when the model tracks down the runway, but is pointed slightly into the wind. The wings are level.
2) A "sideslip" will have the fuselage pointed down the runway, the upwind wing down somewhat, and opposite rudder to oppose any turn.
3) Wind WILL NOT "get under" a wing and "flip" a model or such...not when it's in the air...unless you have fairly significant gusting.
4) A flying model WILL NOT "weathervane" into the wind, unless you have significant gusting.
When landing in a crosswind, you can do different things:
1) Crab the model so that it will track properly down the final approach slope with the wings level. You basically need to keep it level. Don't bother to change the angle, and land normally. There will be a slight side-ways skidding because the model wasn't lined-up correctly. For a lot of sport models with tri-gear, this is OK. You'll land the model safely, and the gear geometry will straighten-out the model.
2) Do the same thing as above, but just before touchdown, use the rudder to turn the nose so that the fuselage aligns with th4e runway. You will need to apply opposite aileron to keep the wings level. This is a common full-size landing technique.
3) Crab the model mostly down the final approach slope. As you near the runway, transition to a forward slip. You will align the nose down the runway. Tilt the upwind wing down to make the model want to traverse upwind, and apply opposite rudder to stop the turning tendency. So if the wind is from the model's right, you'll apply right aileron and left rudder. You'll need to jockey the amount of aileron and rudder to accomodate wind changes. When you land, keep holding in the aileron and rudder. The model will touch the upwind wheel first, then the downwind. Hold in whatever controls are needed to keep the wings level and the nose tracking straight. This technique takes a lot of practice and skill, but rewards the modelers with nice-looking landings.
Your goal is to have the model touch down with the fuselage aligned with the runway and no sideways drift. This is a LOT harder to do than it sounds. The gustier the day, the more difficult. Tri-gear airplanes can land with a bit of drift and be OK. Tail-draggers will usually present a bit of a problem if they land with some drift. You'll be busy trying to keep it rolling straight. Too much drift will wind up in a groundloop and a damaged or destroyed model. Landing on grass is easier in crosswinds than pavement. A grass surface has some 'give' which will allow deficiencies in technique to pass.
It all comes down to doing what you have to do to make the model go where you want it.
For good explanations of what's happening, pick up a copy of 'Stick and Rudder' by Wolfgang Langeweische. It's the definitive book on how an airplane flies, from the pilot's perspective. It's not a scientific text on aerodynamics, but discusses how things look and feel from the pilot's view. An excellent way for modelers to learn how an airplane really flies, instead of learning the many, many misconceptions modelers pick up.
1) A "crab" is when the model tracks down the runway, but is pointed slightly into the wind. The wings are level.
2) A "sideslip" will have the fuselage pointed down the runway, the upwind wing down somewhat, and opposite rudder to oppose any turn.
3) Wind WILL NOT "get under" a wing and "flip" a model or such...not when it's in the air...unless you have fairly significant gusting.
4) A flying model WILL NOT "weathervane" into the wind, unless you have significant gusting.
When landing in a crosswind, you can do different things:
1) Crab the model so that it will track properly down the final approach slope with the wings level. You basically need to keep it level. Don't bother to change the angle, and land normally. There will be a slight side-ways skidding because the model wasn't lined-up correctly. For a lot of sport models with tri-gear, this is OK. You'll land the model safely, and the gear geometry will straighten-out the model.
2) Do the same thing as above, but just before touchdown, use the rudder to turn the nose so that the fuselage aligns with th4e runway. You will need to apply opposite aileron to keep the wings level. This is a common full-size landing technique.
3) Crab the model mostly down the final approach slope. As you near the runway, transition to a forward slip. You will align the nose down the runway. Tilt the upwind wing down to make the model want to traverse upwind, and apply opposite rudder to stop the turning tendency. So if the wind is from the model's right, you'll apply right aileron and left rudder. You'll need to jockey the amount of aileron and rudder to accomodate wind changes. When you land, keep holding in the aileron and rudder. The model will touch the upwind wheel first, then the downwind. Hold in whatever controls are needed to keep the wings level and the nose tracking straight. This technique takes a lot of practice and skill, but rewards the modelers with nice-looking landings.
Your goal is to have the model touch down with the fuselage aligned with the runway and no sideways drift. This is a LOT harder to do than it sounds. The gustier the day, the more difficult. Tri-gear airplanes can land with a bit of drift and be OK. Tail-draggers will usually present a bit of a problem if they land with some drift. You'll be busy trying to keep it rolling straight. Too much drift will wind up in a groundloop and a damaged or destroyed model. Landing on grass is easier in crosswinds than pavement. A grass surface has some 'give' which will allow deficiencies in technique to pass.
It all comes down to doing what you have to do to make the model go where you want it.
For good explanations of what's happening, pick up a copy of 'Stick and Rudder' by Wolfgang Langeweische. It's the definitive book on how an airplane flies, from the pilot's perspective. It's not a scientific text on aerodynamics, but discusses how things look and feel from the pilot's view. An excellent way for modelers to learn how an airplane really flies, instead of learning the many, many misconceptions modelers pick up.
06-15-2006, 06:12 PM
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RE: Crosswind Landings - Crab or side slip??
Crabbing is much easier than slipping. If I just want to get the plane down, I crab it all the way in. Trying to straighten the plane at the last second doesn't always go well. The plane immediately starts drifting, which puts the same strain on the LG at touchdown as a crabbed landing, and the plane's momentum tends to keep it going off the side of the runway. Mostly I avoid crosswind landings. I practice slipping on calm days, and try not to fly in anything that exceeds the maximum demonstrated crosswind for a .40-sized trainer.
06-15-2006, 07:03 PM
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RE: Crosswind Landings - Crab or side slip??
Sideslips are good for aircraft that does not have flaps or spilers if one want to steepen the approach without speed build-up.
Crabbing is no big deal at all. If there is a side wind component, you simply approach the runway at a slight angle while descending in the normal. There is no need to apply rudder or ailerons to "crab". You simply fly the plane slightly off-course.
For example, if there is a 5 mph side wind component and my approach speed is 25 mph, I need to align the heading of the aircraft to be a little bit more than 10 degrees off-course in order to approach the runway.
When you do get close to the ground the wind speed usually gets less and you may have to make some course adjustments.
/Red B.
Crabbing is no big deal at all. If there is a side wind component, you simply approach the runway at a slight angle while descending in the normal. There is no need to apply rudder or ailerons to "crab". You simply fly the plane slightly off-course.
For example, if there is a 5 mph side wind component and my approach speed is 25 mph, I need to align the heading of the aircraft to be a little bit more than 10 degrees off-course in order to approach the runway.
When you do get close to the ground the wind speed usually gets less and you may have to make some course adjustments.
/Red B.
06-15-2006, 07:58 PM
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RE: Crosswind Landings - Crab or side slip??
way WAY overcomplicating this folks..
If you want to land in a crosswind you simply start your approach a little farther in(closer to the pilots side of the runway on an outgoing crosswind) or out (on the other side of the runway on an imcoming crosswind).. You just ease in the rudder to hold heading for approach and let the plane work with the wind, let the wind push the plane just a little. If you time it just right the plane ends up right over the runway facing straight ahead and very slightly (I hate to use this word here) "slipping" in or out as it touches down. It will sit right down and roll straight out.
Piece of cake.
Dont let this confuse what I have said above.
I understand all of the discussion about slip and crab and its really interesting and good learning, but for newbies its really not all that complicated to land in a crosswind. Its a visual thing, you simply do as I said.. You start your approach too far in or out so that you only need enough rudder to keep the plane from weathervaning (yes that is right weathervaning). You hold in the rudder to keep the nose pointing straight ahead and let the plane make its own way right over the runway. Just as the wheels are about to touch the ground you ease out of the rudder and it will settle right in. Then you may need to get back on the rudder a little just for steering purposes.
The only time you are really going to need to slip, crab or whatever you want to call it is when the wind really kicks up.. 15-20+ MPH. In those winds you will need to keep the nose of the plane slightly pointed into the wind and a little bit of throttle on to keep the wind from pushing you off of the runway.
That being said, slipping in to land looks cool and its fun. Its definitely worth learning how to do. [8D]
If you want to land in a crosswind you simply start your approach a little farther in(closer to the pilots side of the runway on an outgoing crosswind) or out (on the other side of the runway on an imcoming crosswind).. You just ease in the rudder to hold heading for approach and let the plane work with the wind, let the wind push the plane just a little. If you time it just right the plane ends up right over the runway facing straight ahead and very slightly (I hate to use this word here) "slipping" in or out as it touches down. It will sit right down and roll straight out.
Piece of cake.
Dont let this confuse what I have said above.
I understand all of the discussion about slip and crab and its really interesting and good learning, but for newbies its really not all that complicated to land in a crosswind. Its a visual thing, you simply do as I said.. You start your approach too far in or out so that you only need enough rudder to keep the plane from weathervaning (yes that is right weathervaning). You hold in the rudder to keep the nose pointing straight ahead and let the plane make its own way right over the runway. Just as the wheels are about to touch the ground you ease out of the rudder and it will settle right in. Then you may need to get back on the rudder a little just for steering purposes.
The only time you are really going to need to slip, crab or whatever you want to call it is when the wind really kicks up.. 15-20+ MPH. In those winds you will need to keep the nose of the plane slightly pointed into the wind and a little bit of throttle on to keep the wind from pushing you off of the runway.
That being said, slipping in to land looks cool and its fun. Its definitely worth learning how to do. [8D]
06-16-2006, 11:48 AM
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RE: Crosswind Landings - Crab or side slip??
ORIGINAL: MikeEast
... You start your approach too far in or out so that you only need enough rudder to keep the plane from weathervaning (yes that is right weathervaning). You hold in the rudder to keep the nose pointing straight ahead and let the plane make its own way right over the runway. ...
... You start your approach too far in or out so that you only need enough rudder to keep the plane from weathervaning (yes that is right weathervaning). You hold in the rudder to keep the nose pointing straight ahead and let the plane make its own way right over the runway. ...
/Red B.
06-16-2006, 12:32 PM
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RE: Crosswind Landings - Crab or side slip??
The last time out we had about a 15mph cross from my back across the runway... So I started
making T&G's and practicing... " What ever you call it"
... It was fun, and the plane looks
kinda kewl (UCD46)..... I never really got it down good(what ever you call it) but the touch
down was fine... It's good to learn... On one of my apporches.. I was "trying" to work the sticks..
And I almost weathervaned, crabed, slipslid, dumb thumbs or whar ever, into the top of the fence
power really comes in handy here[X(]
I also just like to cut the apporch short.. real short, but with the "Do" you can do that
making T&G's and practicing... " What ever you call it"
... It was fun, and the plane lookskinda kewl (UCD46)..... I never really got it down good(what ever you call it) but the touch
down was fine... It's good to learn... On one of my apporches.. I was "trying" to work the sticks..
And I almost weathervaned, crabed, slipslid, dumb thumbs or whar ever, into the top of the fence
power really comes in handy here[X(]
I also just like to cut the apporch short.. real short, but with the "Do" you can do that
06-16-2006, 12:55 PM
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RE: Crosswind Landings - Crab or side slip??
ORIGINAL: Red B.
There is no such thing as weathervaning when flying in a crosswind. This has previously been discussed at length in the aerodynamic forum.
/Red B.
ORIGINAL: MikeEast
... You start your approach too far in or out so that you only need enough rudder to keep the plane from weathervaning (yes that is right weathervaning). You hold in the rudder to keep the nose pointing straight ahead and let the plane make its own way right over the runway. ...
... You start your approach too far in or out so that you only need enough rudder to keep the plane from weathervaning (yes that is right weathervaning). You hold in the rudder to keep the nose pointing straight ahead and let the plane make its own way right over the runway. ...
/Red B.
. You tell me what your personal experience is and I would be a lot more inclined to listen. Im almost positive that when it comes right down to it, your crosswind landing stick inputs are about the same as mine if you can consistantly land smoothly and make the landing appear nothing more than a basic landing on a calm day. If you want to land gently in the center of the runway on a crosswind its real simple. You bring it
06-16-2006, 02:45 PM
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RE: Crosswind Landings - Crab or side slip??
ORIGINAL: MikeEast
Respectfully, I dont care what the aerodynamic forum discussed, I know what the airplane does when its on approach and I know what it does when its in flight, I see it all the time when I'm flying in a crosswind. I fly enough to know what I see and what I deal with in crosswinds. You can talk theories and give expert accounts all daybut I know what happens and I dont give a flip what the general concensus is becuase I see it and deal with it with my own eyes. You tell me what your personal experience is and I would be a lot more inclined to listen. Im almost positive that when it comes right down to it, your crosswind landing stick inputs are about the same as mine if you can consistantly land smoothly and make the landing appear nothing more than a basic landing on a calm day.
Respectfully, I dont care what the aerodynamic forum discussed, I know what the airplane does when its on approach and I know what it does when its in flight, I see it all the time when I'm flying in a crosswind. I fly enough to know what I see and what I deal with in crosswinds. You can talk theories and give expert accounts all daybut I know what happens and I dont give a flip what the general concensus is becuase I see it and deal with it with my own eyes
. You tell me what your personal experience is and I would be a lot more inclined to listen. Im almost positive that when it comes right down to it, your crosswind landing stick inputs are about the same as mine if you can consistantly land smoothly and make the landing appear nothing more than a basic landing on a calm day.
Because you questioned my findings I called a friend of the family who is a Swedish Air Force Pilot who has done quite a lot of work with flight testing. He is a graduate of the US Navy Test Pilot School (mid-eighties). According to him, aircraft does not wheatercock due to crosswinds as long as the winds speed is constant. They drift, but they do not alter their compass heading because of the wind. However, if there is an appreciable wind speed gradient one must adjust the crab angle as the aircraft descends.
Take it or leave it, I couldn't care less!
/Red B.
06-16-2006, 02:45 PM
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RE: Crosswind Landings - Crab or side slip??
I'm not sure "weathervaning" is a technical term, but I believe the areodynamicists will tell you there's no "wind" on a flying plane, other than the one caused by the motion of the plane itself, which is always head-on. So there's nothing forcing the plane to turn. But that assumes a steady-state condition, or a plane with zero inertia. It doesn't account for gusts and the fact that my planes may be less-than perfectly straight.
06-16-2006, 04:15 PM
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RE: Crosswind Landings - Crab or side slip??
Im really not sure weathervaning is a technical term either but it works ok for the purpose we highly technical RC airplane folks use it for. [8D]
If that were true then crosswind landings would not be an issue. The fact that the wind is not head on, but is pushing the air into the side of the airplane forcing it inward or outward is what makes it a "cross wind".
When is a crosswind ever constant? That is the BIGGEST part of what makes a crosswind landing difficult to manage. That is, the fact that its constantly gusting unpredictably causing the pilot to have to constantly make small adjustments to compensate for varying wind.
I will give you that IF the wind is crossing at a constant speed and the planes speed is constant that it will not be in a constant weathervane position where the fuselage is slight off center of its yaw axis. But everytime you get a gust, or a sudden decrease in wind that big old slab of wood that is like a billboard on the rear end of the airplane is going to react to the change in wind force against it. .
I'm not sure "weathervaning" is a technical term, but I believe the areodynamicists will tell you there's no "wind" on a flying plane, other than the one caused by the motion of the plane itself, which is always head-on.
According to him, aircraft does not wheatercock due to crosswinds as long as the winds speed is constant.
I will give you that IF the wind is crossing at a constant speed and the planes speed is constant that it will not be in a constant weathervane position where the fuselage is slight off center of its yaw axis. But everytime you get a gust, or a sudden decrease in wind that big old slab of wood that is like a billboard on the rear end of the airplane is going to react to the change in wind force against it. .
06-16-2006, 05:39 PM
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RE: Crosswind Landings - Crab or side slip??
Well, just for discussion and not to ruffle feathers.
I have actually done extensive research on wind effects on aerodynamic bodys.
Weathervaning may or may not be a technical term but it does have an effect on all objects with airflow accross them.
It has little to no effect on a "flying plane" meaning a wing, it does have an effect on other surfaces. Namely the fuselage and vertical stab. This effect can be more or less dramatic based mainly on 2 factors.
1. shape, size and location of vertical surfaces effected by non linear airflow.
2. Center of gravity of any airborn object in relation to the aerodynamic center of pressure. (the farther forward the CG is ahead of the center of pressure the more likely weathervaning will occur)
The great thing about controlled flight is you can overcome these forces.
It can suck when I launch a rocket I have several hundred dollars invested in. (I have no control over my rockets once they leave the pad)
I have actually done extensive research on wind effects on aerodynamic bodys.
Weathervaning may or may not be a technical term but it does have an effect on all objects with airflow accross them.
It has little to no effect on a "flying plane" meaning a wing, it does have an effect on other surfaces. Namely the fuselage and vertical stab. This effect can be more or less dramatic based mainly on 2 factors.
1. shape, size and location of vertical surfaces effected by non linear airflow.
2. Center of gravity of any airborn object in relation to the aerodynamic center of pressure. (the farther forward the CG is ahead of the center of pressure the more likely weathervaning will occur)
The great thing about controlled flight is you can overcome these forces.
It can suck when I launch a rocket I have several hundred dollars invested in. (I have no control over my rockets once they leave the pad)
06-16-2006, 07:27 PM
#18
RE: Crosswind Landings - Crab or side slip??
It can suck when I launch a rocket I have several hundred dollars invested in.
It has little to no effect on a "flying plane" meaning a wing, it does have an effect on other surfaces. Namely the fuselage and vertical stab.
06-16-2006, 08:59 PM
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RE: Crosswind Landings - Crab or side slip??
It has little to no effect on a "flying plane" meaning a wing, it does have an effect on other surfaces. Namely the fuselage and vertical stab.
The vertical stab ensures the plane's center of pressure is behind the c.g., and behind the LG. This causes the plane to point into the wind. On the ground, the result is weathervaning. In the air, because the wind is always on the nose (except for the aforementioned gusts), the result is a plane that flies in a straight line.
06-16-2006, 09:41 PM
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RE: Crosswind Landings - Crab or side slip??
Fact is, a plane is affected by a crosswind. It exerts pressure on the fuselage and vertical stabilizer. If a plane is moving at 30mph with a right crosswind at 5mph, the combination of these two vectors result in an apparent wind coming from slightly to the right of the nose of the airplane. This apparent wind exerts a force on the right side of the plane which disproportionately affects the area to the rear of the center of gravity due to its size relative to the area in front of the center of gravity. This force causes the nose of the plane to turn slightly into the crosswind until the relative wind is on the nose. The plane then flys in a straight line albeit with a crab angle (the nose is pointing in a different direction than the plane is flying). The faster the plane flys, the less the crab angle because the relative wind moves closer to the nose and vice versa.
Back the original question, I alow the plane to descend in a crab angle until the flare, then I use the rudder to point the nose at the center of the runway, and use the aileron to slightly lower the upwind wing. This keeps the plane on the center line until touchdown. This is the way I was taught to crosswind land in the Air Force.
Back the original question, I alow the plane to descend in a crab angle until the flare, then I use the rudder to point the nose at the center of the runway, and use the aileron to slightly lower the upwind wing. This keeps the plane on the center line until touchdown. This is the way I was taught to crosswind land in the Air Force.
06-16-2006, 09:50 PM
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RE: Crosswind Landings - Crab or side slip??
For a new pilot, and ten landings is a very new pilot, I would suggest the crab. The crab is the easiest and the most natural for the beginner. And tricycle landing gear aircraft can be landed in the crab. As soon as the mains touch the runway, the nose will pivot around on its own.
06-16-2006, 10:12 PM
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RE: Crosswind Landings - Crab or side slip??
If a plane is moving at 30mph with a right crosswind at 5mph, the combination of these two vectors result in an apparent wind coming from slightly to the right of the nose of the airplane.
There's a book on relativity by a guy named Einstein who explains this better than I can. (Skip the speed-of-light stuff, though--not relevant here).