Crosswind Landing

[A300Capt]

Just curious, is there something about flying transport category aircraft that make the aerodynamics of crosswind landings different than general aviation aircraft?

The reason I ask is because it seems as though some posters who fly RJs and such act as if the "slip" and "crab and kick" methods are distinctly different. From everything I can tell, they're identical at the moment of touchdown...or at least they should be.

The wings will be in the same attitude, the upwind wheel will touch down first, the controls will be equally effective, speeds will be identical, etc. regardless of the method used. At least this is how it is for general aviation birds. In small planes, really the only distinction between the two methods is when the side slip is initiated, sooner or later...yet in both cases, the aircraft will be in an identical side slip at the moment of touchdown. I don't understand how things like scraping a wingtip or engine pod have anything to do with the crosswind technique used.

Does the larger mass or swept wings of airliners somehow change their crosswind handling characteristics?

It's basically the amount of bank used at the moment of touchdown regardless of method used. It's okay and preferable to land in a crab during xwind conditions when braking action is less than good such as wet/cluttered conditions. Obviously, the less the aircraft can be banked equals a greater crab that is required at touchdown.

Four engine aircraft (747, DC8, 707..etc) don't allow for much bank angle close to the ground whether you use the sideslip or kickout in the flare method. The outside pod engines will generally strike first and I know the DC8 is super critical here. I've been told you're limited to about 5 degrees of bank before an engine strike occurs. Those aircraft that sit on short gear legs and low hung wings (B727, DC9 and RJ's) could possible hit a TE flap or wingtip if banked too much so a slight crab is preferable. The B757 and A300 sit on tall gear legs and high wingtips that allow for more bank angle and clearance.

I prefer the kickout method and I suspect most 121 guys/gals use that method at least from my experience and observation. The sideslip down final method can be very uncomfortable for the passengers and is generally not used.

 

[Douglas]

So, there is an argument between me and the guy who said that the ice would fly off at 12,000ft. It's been my impression that on a crosswind approach to landing, it is best to crab into the wind, "weathervane", I think is the technical term. I was told that I was wrong and that it is best to use the "wing down, top rudder" technique by essentially aileron-ing into the wind and using rudder to maintain directional control with the nose pointing towards the runway.

I personally think that crabbing into the wind is more fun but I have never been given any formal training on approach to land in a crosswind (I know, it's pathetic) so I have always just done what "felt right". I have used both techniques mentioned above, and both seem to work perfectly fine, but what is the right way?

I second that if you can do what you want.
Just once you get in the teaching environment, it is much easier to teach crosswind landings if they are in slip for an exaggerated distance. Then once the get better, you can work them in closer with the crab. :bandit:

 

[ppragman]

Beyond the fact that I really can't slip the airframe I fly now, from a passenger comfort point of view, it doesn't make sense to go into a slip at the FAF.

What are you flying now?

 

[BobDDuck]

Arctic RJ

 

[ppragman]

Arctic RJ

CRJ?

 

[Trip7]

CRJ?

Yes....

 

[ppragman]

Yes....

Well, I don't know all this SJS terminology, I live in the arctic and have never seen a CRJ leave ANC.

 

[Trip7]

Well, I don't know all this SJS terminology, I live in the arctic and have never seen a CRJ leave ANC.

I was in Montreal the other day and that place definitely qualifies as arctic. No need to go all the way to ANC for that

 

[granlistillo]

The reason I ask is because it seems as though some posters who fly RJs and such act as if the "slip" and "crab and kick" methods are distinctly different. From everything I can tell, they're identical at the moment of touchdown...or at least they should be.

Correct at touchdown they are the same. At the moment of touchdown, you are cross controlling to align the gear bogies straight down the runway with no drift. Drift or landing in a crab will put a side load on the gear.

Basically in a CRJ, especially the 200 where the wingtips are close to the ground you must kick it straight at the last second. When I hear "10" on the rad alt I kick the nose straight. Like any airplane, you yaw it and the opposite wing will rise (upwind wing)You MUST counteract it with aileron.

So I guess with the CRJ you try to land as wings level with possible. rudder to align the plane down the runway and aileron to keep the near wings level to a slight upwing down to counteract drift. Also, in a stiff xwind I let the plane settle a bit (not slam it in, but not try to grease it either)so that a gusting wind will have less time to play havoc if you start floating.

My answer may not be totally correct and I am not the most experience CRJ guy here buy a long shot, but I agree with the Duck on this one. I couldnt imagine trying to do a side slipped landing in this airplane. I think the sink rate induced by a slip outside of the flare would only start setting the EGPWS off.

 

[SmoothLanderJ]

Im glad this thread is still going:


You can never have too many cosswind landing under your belt. So, yesterday in DTW they we were landing 21L and the winds were something like 250 at 23 gusting to 32. The funny thing is I remembered this thread while on the approach, ha!

Long story short the approach was fine all the way until the transition from the crap to the slip. Apparently I overestimated the crosswind and was blown off center line just a bit. I was pretty pissed about it but the Captain was like "Eh that was fine, now you know next time" So when it comes to landing in the crosswind Im always trying to make each time better than the last.

 

[SpiceWeasel]

Im glad this thread is still going:


You can never have too many cosswind landing under your belt. So, yesterday in DTW they we were landing 21L and the winds were something like 250 at 23 gusting to 32. The funny thing is I remembered this thread while on the approach, ha!

Long story short the approach was fine all the way until the transition from the crap to the slip. Apparently I overestimated the crosswind and was blown off center line just a bit. I was pretty pissed about it but the Captain was like "Eh that was fine, now you know next time" So when it comes to landing in the crosswind Im always trying to make each time better than the last.

Do you ever land it with a crosswind more than max demonstrated? I ask because we received notification recently that the FAA had been "observing" our landings. hah. And so now we treat the max demonstrated as a limitation.:banghead:

 

[SmoothLanderJ]

Do you ever land it with a crosswind more than max demonstrated? I ask because we received notification recently that the FAA had been "observing" our landings. hah. And so now we treat the max demonstrated as a limitation.:banghead:

Not yet, but yesterday was pretty intersesting. I havent heard anything about the FAA looking in but ill make sure im on the ball.

 

[Polar742]

Xwind limits are demonstrated when the company wants you to go, and limits if you bend metal. :crazy:

 

[jrh]

Correct at touchdown they are the same. At the moment of touchdown, you are cross controlling to align the gear bogies straight down the runway with no drift. Drift or landing in a crab will put a side load on the gear.

...

So I guess with the CRJ you try to land as wings level with possible. rudder to align the plane down the runway and aileron to keep the near wings level to a slight upwing down to counteract drift.

This is the part I still don't understand.

If the wings are level, how can the plane remain over and aligned with the runway centerline?

When side slipping an aircraft, the pilot is basically using the horizontal component of lift to counteract the crosswind component. The bank angle of the wings determines the amount of horizontal lift (thus, a steeper bank angle for a stronger crosswind). The net effect is that the aircraft travels straight over the ground. But if the bank angle is zero, there is no horizontal component of lift. With no horizontal component of lift, the plane would begin drifting to the side, which would place a side load on the gear at the moment of touchdown.

The only explanation I can think of is that for the moment when the rudder is applied, the nose of the aircraft yaws to the side, yet the momentum of the aircraft makes it continue straight down the runway for a few seconds. Another way to think of this is that the plane is making a skidding turn and the crosswind is "flattening" the arc of the turn for a few seconds as the turn is initiated, and this flat spot in the turn is aligned with the runway. As long as the touchdown occurs within these few seconds, there will be no side loading.

Does this sound accurate?

I wish tgrayson or some other aerodynamic guru could chime in on this.

 

[tgrayson]

As long as the touchdown occurs within these few seconds, there will be no side loading. Does this sound accurate?

You've got it. If you wait to the last minute to kick the rudder, the aircraft won't have time to develop much drift.

You certainly don't have to do it this way. I know lots of CRJ pilots who just transition to the wing low method close to the runway. And I know one who just lands slightly crabbed.

Part of the motivation of many "kick out" pilots is that they're a bit paranoid about putting a swept wing aircraft into a slip of any kind. One new FO here told me that a buddy of his had the airplane taken away from him by the Captain when he started to use the wing low method.

 

[Polar742]

You've got it. If you wait to the last minute to kick the rudder, the aircraft won't have time to develop much drift.

You certainly don't have to do it this way. I know lots of CRJ pilots who just transition to the wing low method close to the runway. And I know one who just lands slightly crabbed.

Part of the motivation of many "kick out" pilots is that they're a bit paranoid about putting a swept wing aircraft into a slip of any kind. One new FO here told me that a buddy of his had the airplane taken away from him by the Captain when he started to use the wing low method.

I don't think that is a fair assessment.

Again, it is dependent on equipment. There may be some CRJ pilots that do the wing low method, as we do on the 747 if the wind is very light. However, anything with any decent amount of wind, the bank angle will put you close to the limit angle to striking the ground. Do you really want to use 3* of bank if you strike metal at 6*? Plus, on jets with spoiler mixing, your yoke deplacement will probably be very close to deploying spoilers. I'm sure every CRJ operator has had the same wing damage issues that BobDDuck shared, thus the paranoia of your friend's Captain. I sure wouldn't want to be the guy who's FO was using 1/2 of the bank angle allowable, then realizes he's drifted off centerline, increases the bank angle and whacks a wing. It's a lot easier, and safer, not to do that in some airplanes.

As to being scared, I saw more ignorance of swept-wing aerodynamics in regards to slips than not. I've seen forward slips and excessive sideslips that are uncessary, or just not working for the situation, more often than being scared of a slip (at the reginal job, since that seems to be the focus)

 

[tgrayson]

IHowever, anything with any decent amount of wind, the bank angle will put you close to the limit angle to striking the ground. Do you really want to use 3* of bank if you strike metal at 6*?

The CRJ does not contain any limitation in this regard and you can use the wing low method until you reach the crosswind limitations of the airplane (so I am told).

thus the paranoia of your friend's Captain.

No, that was not the reason for the paranoia. The captain was afraid of a wingtip stall and having the airplane flip on its back, a concern which appears to be pretty common.

I understand that *some* airplanes do have bank angle limitations near the ground and you should know if you're flying one of those. But for other airplanes, many pilots appear to be using the wing low method just fine. I believe an MD11 Captain mentioned when this subject came up a while back that the autoland will transition to a sideslip something like 100 feet above the ground.

 

[Polar742]

The CRJ does not contain any limitation in this regard and you can use the wing low method until you reach the crosswind limitations of the airplane (so I am told).

I was just basing the CRJ info off BobDDuck's post:

If you try that with the small version of the Arctic RJ you WILL drag a wingtip. When we went through a hiring boom earlier this year we had three of four wing strikes because of new guys trying to land it like they were still in a 172.

I've been told 5 degrees. Jeremy can probably correct me if that's not it.

No, that was not the reason for the paranoia. The captain was afraid of a wingtip stall and having the airplane flip on its back, a concern which appears to be pretty common.

Well, if it wasn't for that, the training department would be bored :bandit:. There was nothing worse than having to reach back into my marginal highspeed aero knowledge and draw diagrams relating to spanwise flow and crosswinds at takeoff and landing during recurrent. I fault the initial training, but I digress.

I understand that *some* airplanes do have bank angle limitations near the ground and you should know if you're flying one of those. But for other airplanes, many pilots appear to be using the wing low method just fine. I believe an MD11 Captain mentioned when this subject came up a while back that the autoland will transition to a sideslip something like 100 feet above the ground.

I think it might have been our laziest 747 FO that had that tidbit in this thread :

The 747 (anectodally the DC-8, but I've never laid hands on one...just the 'old-timers' stories about it), we are taught to land in a crab, kick the crab out just before touchdown, but slipping is dangerous as you might (and it has been done many, many times) drag a pod. Oddly enough, in a 25 knot cross (max for autoland) the jet will start a slip anywhere from 200 to 500 feet.

Regardless of our debate, if you land it in the touchdown zone, on the centerline and not bend metal, it was a good one.

If you don't accomplish all of the above, you could be at the end of a long table with lawyers in suits trying to explain why the aluminum got a racing stripe.....

 

[B767Driver]

Bottom line....you never land in a crosswind with wings level. Upwind wing down, rudder to keep the nose straight. After landing....ailerons fully deflected into the wind. If there are wing strike issues....these will be reflecting in crosswind limitations.

HOWEVER, there are some airplanes with castering main gear that will permit a touchdown in a crab. I remember the 737 was one of them. That's why when you are taxiing behind a 737, many times they look really goofy...the nose will be pointed in a different line than the taxi line.

If your airplane is not of this type...then always wing down at touchdown...don't ever remove the upwind aileron!

 

[Trip7]

Bottom line....you never land in a crosswind with wings level. Upwind wing down, rudder to keep the nose straight. After landing....ailerons fully deflected into the wind. If there are wing strike issues....these will be reflecting in crosswind limitations.

HOWEVER, there are some airplanes with castering nosewheels that will permit a touchdown in a crab. I remember the 737 was one of them. That's why when you are taxiing behind a 737, many times they look really goofy...the nose will be pointed in a different line than the taxi line.

If your airplane is not of this type...then always wing down at touchdown...don't ever remove the upwind aileron!

Good advice. Thats another way to drag a wingtip if you don't adhere