Cross wind landing ... again

[PRB]

I think I just had an “aha” moment when it comes to cross wind landings. What I have been doing is simply steering into the wind so that my direction of motion is down the runway. This “easy method” is great, until your wheels hit the runway pointed in that “un-natual” direction...

I knew of this other method of crabbing, but could never get it to work. I think I know why now... Say the wind is pushing me to the left. When trying to employ the crabbing method, I would get lined up, then step on the right rudder pedal, to point the bird into the wind, then apply opposite aileron to keep the wings level. This never worked!

I was thinking about it today (again) and it suddenly struck me that I was doing it backwards! So I tried this: Point the plane into the wind such that my direction of motion is down the runway. At this point my nose is pointed off to the right, right? Then, step on left rudder to point the nose down the runway, applying right aileron to keep the wings level. It worked better. I think... Learning how much rudder and aileron to apply is a little tricky, because too much or too little still results in a off centered “motion vector”, and FUBAR'd approach, but I think I finally figured this out!

All you real pilots out there feel free to point out if I'll still messed up in my thinking... (not unusual)

 

[fliger747]

Paul:

Yep, that's the way it is normally done. There are some combinations and variations. a limiting factor is how much bank is allowed due to aircraft configuration. Wingtips and engine pods are important limiting items. With the 747 we can only have about 6 degrees bank without danger of striking an ouboard pod. So with a heavy aircraft, intertia can be your friend. In strong winds, the crab/slip can be maintained and any remaining misalignment with the runway kicked out at the last moment without developing any sideways drift.

Cheers: T

 

[PRB]

Well that's interesting – 6 degrees? That doesn't seem like much. So what about those landings we've seen on YouTube of 747s landing at the old Hong Kong airport? They looked like way more than 6 degrees. Come to think of it, I seem to remember some engine nacelles dragging on the runway too, or almost...

About the crabbing. I'm guessing that over time, the engine pointed off the “motion vector” will tend to bend that vector to it's direction (thrust vector?), and that the crab must have to be constantly “updated” for this. And I did, at the last instant, step on the rudder harder to line the wheels with the direction of the runway a little more...

 

[Brett_Henderson]

You've got a real good grasp on the theories

I'll just fine-tune the terminology... A 'crab' is nothing more than a heading that compensates for the wind so that you maintain a desired track. No rudder or aileron involved. That's what you're flying early in a X-wind approach (and on any of the pattern legs if needed). It the same as a long leg of a flight with a X-wind.

Now, when you start introducing ailerons and rudder, it becomes a 'slip'. Unless it's a strong cross-wind.. it's just like any other landing. At some point you start keeping the mass of the airplane on runway center-line, AND start aligning the nose for runway heading. You really don't want to think about the fact that you're cross-controlling.. you just keep on using ailerons for center-line.. rudder for runway heading. If done properly (in a steady X-wind), you'll land with the upwind wing slightly lowered, touching one main-wheel at a time.. (in a light, single-engine )..

Then after both wheels are down, you go from slight aileron deflection, to full deflection into the wind, until airspeed is low enough that a wind gust won't lift the upwind wing.

Because of this slipping, it's also normal to carry a few extra knots on final.. gives you a margin for error.

 

[PRB]

Thanks, Brett. That's a good explanation. So, it makes sense to introduce the slip only when you have to, late in the landing. Until that point, one could just crab on in....

 

[Brett_Henderson]

Oh.. and the thrust is always aligned the the airplane. The prop and engine have no idea how they're moving relative to the ground. They don't even know there's a X-wind.. nor does the airplane. The wind to an airplane, is like the water to a fish in a giant aquarium. The fish swimming north-to-south has no idea that the aquarium is moving east-to-west.

 

[Brett_Henderson]

Thanks, Brett. That's a good explanation. So, it makes sense to introduce the slip only when you have to, late in the landing. Until that point, one could just crab on in....

Welll.. that's an age-long aviation debate. I'm a fan of slipping as early as the wind allows... With a strong wind, you risk running out of rudder if you start too early. Some people like to wait til the last minute before just kicking the tail into alignment.. I don't like that method because for one, if it's a gusty wind, you're better off getting a feel for it early.. And for two.. passengers don't like seeing the runway out the side window when you're just crabbing.

 

[Ken Stallings]

PRB,

Correct except for one point ... you do not bank to keep the wings level, but in fact you bank into the wind. In your left crosswind, you do bank the wings to the right.

Here is how you perform a crosswind landing in a GA airplane. The lighter the aircraft, generally the more difficult the crosswind landing is to perform.

You can crab into the wind while on final approach to avoid a sideloading slip. This is generally much more comfortable for your passengers, though in FSX that doesn't matter.

However, you cannot land a GA airplane in a crab. As you said, you must touchdown with the nose and the motion of the aircraft lined up down the runway. You do this by slipping into the wind. This is how you do that ...

You use rudder to point the nose of the aircraft down the runway axis.

You then use alieron bank to provide a force into the direction of the wind.

The proper combination of the two at the same time, allows the upwind wheel to touchdown first. Then as the aircraft loses lift, it forces the other main gear on the surface later on.

Your bank into the wind counters the force of the crosswind. Your rudder in the opposite direction of the bank keeps the nose pointed down the runway so that when the upwind wheels makes contact with the runway, your aircraft's wheels are not going to undergo a sideways skid, which can damage the gear and wheels.

You keep your crab until you start your flare, then transition to the slip. With practice, you can time this properly. If you see the aircraft sliding to the left with a left crosswind, you simply increase the level of bank to the right with the aileron. If you see the nose pointed off the runway alignment, then you use the rudder (whichever it takes) to repoint the nose down the runway.

Hope this helps.

Ken

 

[tigisfat]

I consider myself the master of crosswind landings, I've seldom met one I couldn't tame, even if it meant a go around or two. I just get down into ground effect and feel it out using the standard method Ken explained.


I never felt like any MSFS version has ever gotten slips or skids quite right, most specifically in crosswind landing forward slips. There isn't a point of harmony where the aircraft is going straight forward and you've got a wing dipped. I think the effect of the winds is downlplayed to, or something. I dunno. It just doesn't feel right.

 

[Dimus]

I never felt like any MSFS version has ever gotten slips or skids quite right, most specifically in crosswind landing forward slips. There isn't a point of harmony where the aircraft is going straight forward and you've got a wing dipped. I think the effect of the winds is downlplayed to, or something. I dunno. It just doesn't feel right.

I second that. Plus you never have the effect of sudden gusts or change of wind direction or even sudden downdraughts and updraughts that you may find at ends of runways. All these were wild shocks I received when I first tried my hand at real landings under windy conditions, after years of flightsimming.

 

[peter12213]

what I do, whether its right or not is just fly at an angle without any rudder using roll inputs to keep on track then as I get the main wheels down I hit the rudder and straighten up before the nose comes down and any braking has taken place this is how I have seen it done so I just try and copy really, whether as I said earlier this is right or not I'm not sure!

But as has already been said the wind isn't right really, it just doesn't behave like in real life so I don't often fly with it really above 15kts say!

 

[Brett_Henderson]

You keep your crab until you start your flare, then transition to the slip.

This is the age-old debate

I'm a proponent of starting the slip well before the flare. Both the the flare and the slip are "transitions". I'd rather not try to do them simultaneously. And I like getting a feel for the amount of cross-control I'll be dealing with, as early as possible.

It's a personal thing.. neither is totally correct, nor incorrect. The only technique I'd discourage, and even go as far as to say it's "wrong"... is literally waiting until just before the wheels touch, and then jumping on the rudder.

 

[PRB]

Ken – Banking into the wind. I missed that detail. I was just applying enough aileron to keep the wings level. Stupid me, the examples in all the “how to fly” books show the wings banked into the wind, too. Will try that next.
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Tig – I suspect each plane’s flight model could influence how well the slip “works” in FS, as well as the overall FSX “flight engine”. Seems to me some planes can’t even be made to slip in the first place.
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Brett – I’m finding I like getting into the slip early, for exactly the reason you mentioned: to get a feel, early, for how much rudder and aileron to crank in.
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Good stuff, all. Thanks!

 

[Brett_Henderson]

Brett – I’m finding I like getting into the slip early, for exactly the reason you mentioned: to get a feel, early, for how much rudder and aileron to crank in.

As limited as te MSFS fligh-model might be.. this is a technique that will serve you well if you ever take real flying lessons.

The trick to landing in a X-wind, is to not think of it as a X-wind. It's a lot like the 'rule' for landing in general (pitch for airspeed / throttle for altitude), in that you, "aileron for centerline / rudder for heading". Crosswind or not.. that will get you there... and IF there's a X-wind, the one main gear at a time landing, will just happen.

 

[Dimus]

I have found the following planes as simulating forward slip relatively well in FSX:

A2A Cup
Flight Replicas SuperCub
Real Air SF260
Antony's freeware Tiger Moth

There might be others too that I am not aware of.

 

[Trans_23]

Very informative thread. Thanks all!

 

[fliger747]

Paul:

Those videos' of Kai Tek in Hong Kong, are real. However notice that they are landing in a crab, which is actually what Boeing reccomends for the Whale in a big X-wind, scrubs the tires, but the inertia of the plane tends to have it continue straight ahead. I once landed an empty 400 in Luxembourg in a huge rainstorm in luxembourg (the day trees blew down all across Europe) with the wind blowing 50 knots, and not much of a "down the runway" component. Wet pavement is forgiving of some transgressions (as long as you stay out of reverse) much like taildraggers and grass.

Cheers: T

 

[TeaSea]

PRB,

Don't forget you continue to fly the plane even when it's on the ground. Last weekend I watched a guy forget that and after a pretty decent initial touchdown, let the wind get under his upwind wing threatening to flip him over...it did propel him off the runway, across a taxiway and sent him shooting across the field towards a ditch.

Fortunately he managed to get the -172 stopped without hitting the prop or letting it flip, although he was visibly shaking when he got out.

 

[Ken Stallings]

I wil take a consistent crosswind over gusty winds any day. The only two times I've ever gotten concerned landing in a crosswind was because of significant gusts.

First time was when I was flying solo getting my private certificate. Landed just fine and rollers coming across nearby trees caused my aircraft to torque to the right. I applied counter left rudder while in the ground and got it under control.

Second time was the same situation, just minus the trees.

I needed to land at Abilene Regional in a 20 to 22 knot crosswind and I got the upwind (left main gear) to touchdown fine. Then, after the right main touched down a gust of wind put the plane a few feet back into the air and drifting a bit right. Put more bank correction in and kept the nose centered and the plane touched down again. However, the second time I still had a small bit of rudder to the right when the nose wheel touched down and it sent the plane a bit right of centerline. But, I again applied left rudder and re-centered the aircraft.

However, the gusts and crosswind was so powerful that it then tried to weathervane the empennage and vertical stabilizer torqued to the right (counter-clockwise), so I had to put some right rudder in to counter that force. The left wing picked up a small bit but full left aileron kept that under control and quickly stabilized that.

The whole fracas lasted only three seconds. Like was said, you just have to adopt the mindset that you have to fly the aircraft all the way until you reach the parking spot and shut down. In fact, the winds were so bad that since the ramp guy could not tie me down, I stayed in the aircraft while my Grace Flight passenger walked to the aircraft and got in! I just didn't want to leave the airplane and have a gust of wind lift a wing without me putting in the required aileron input to keep the upwind wing on the level.

The most challenging part is the taxi. When your speed reduces down to taxi speed the rudder no longer has the authority to counter the weather vane effect. So, you have to use differential braking while you taxi to provide the required force up front of center gravity to counter all that wind force on the vertical stabilizer and empennage.

The trick there is to keep your taxi speed slow and to always keep full aileron deflection into the wind (yoke turned into the wind for a quartering headwind and opposite the wind for a quartering tailwind).

The "debate" about crap versus slip has many alternate ideas. Either technique can work provided you don't touchdown in a GA airplane in the crab. The big jets have stronger landing gear and are sometimes capable of landing in a crab -- just depends upon the aircraft. No GA airplane I know of is recommended by the manufacturer to land in a crab.

However, the one undeniable truth is that the slip method on final can cause passengers (especially in the rear seats) to feel very uncomfortable. The further aft of center gravity a passenger seats then the more acute the sideways forces in a slip feels. It can lead pax to fill up with anxiety.

Cheers,

Ken

 

[PRB]

... Don't forget you continue to fly the plane even when it's on the ground ...

Now he tells me!

Actually I “knew” this, but this Wildcat is probably not the best plane to be practicing cross wind landings (in the rain). I just finished a book called The Guadalcanal Air War, by Col. Jefferson DeBlanc. He was a USMC ace, and earned the Medla of Honor flying Wildcats over The Slot, and he said the Wildcat was “vicious” in a cross wind landing, with the narrow gear and all...

Fliger - Rgr the 747 landing at Hong Kong. That must put unbelievable stress on the main mounts! They need the B-52 main wheels that swivel!