sstsomeday
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Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 8:15 am

I have seen pictures and videos, here and elsewhere, of these very different landing techniques in a heavy crosswind.

Whereas the dipped wing seems like a very controlled manuver, which touches one main landing gear down before the other, the crab landing seems like a less controlled manouver, the touchdown seems violent and precarious, and from what would guess, stressfull to the A/C structure.

Is the cross wind sometimes too severe, so that the dipped wing landing is insufficiant or risks touching a wingtip or nacelle to the ground?

If so, is the general consernsus that the carb landing is safe, because it looks like a very unstable / cowboy-like manuver. I wonder whether in these kinds of extreme crosswinds a diversion is more prudent? (Of course, I concede I am not an airline pilot and therefore I am asking the question...)
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futureualpilot
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 9:08 am

Usually with an x-wind I use the crab until I'm in the flare, then apply opposite rudder until aligned with the runway centerline and lower the upwind wing into the wind and touchdown on one gear (the upwind gear). This is how I was taught, and when done right it works pretty well. The problem being that it can be somewhat interesting in gusty winds, especially during the flare. So in a nutshell, it is a combination of both, crab and flare. Both are usually taught and practiced, and both are safe. While I don't fly any of the heavy metal just yet, you are probably correct, the wing low method on a low wing aircraft might sometimes be require too much bank (at least for certain aircraft, DC-9 series, ERJ/CRJ, etc) and the wingtip may contact the ground. Of course, this is just my .02!

I would imagine that while sideloading the gear is stressful, it is taken into consideration during design and if you were to land and sideload the gear enough to break it, perhaps you ought not have been attempting to touch down in the first place.

[Edited 2007-03-08 01:11:27]
Life is better when you surf.
 
highflyer9790
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 9:11 am

Quoting SSTsomeday (Thread starter):
Is the cross wind sometimes too severe, so that the dipped wing landing is insufficiant or risks touching a wingtip or nacelle to the ground?

Well, with Commercial aircraft, especially wide bodies, the approach is stabablised so that during the approach the airplane's track is headed toward the runway. while flaring, rudder will be kicked in to align the nose with the center line. other times, more likely with aircraft 737 and smaller, the "wing down, opposite rudder" technique is used, having the nose aligned with the center line from the time this manuver is inputted. Note: Im sure a commercial pilot could explain much better!

As a GA pilot, i perfer the "wing down, opposite rudder." Once established on final, if i have a crosswind from the left, l would use right rudder to align the nose with the center line. however, this alone will cause the plane drift to the right, because the nose is not where it would naturally be to have a track with the runway. So, to avoid that, you input whatever amount of left bank is needed to stop drifting. The goal then is land first on the left wheel, right wheel, nose wheel. Note this scenerio was with a cross wind from the left.

Quoting SSTsomeday (Thread starter):
I wonder whether in these kinds of extreme crosswinds a diversion is more prudent? (Of course, I concede I am not an airline pilot and therefore I am asking the question...)

Each aircraft has a maximum crosswind component. if the crosswind is above that, you MUST divert. of course, each airline varies this according to their SOPs. as expected, and autoland has its own maximums.

hope it helps!

highflyer
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highflyer9790
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 9:16 am

Here are some great videos that have been used at A.net in the past:

Crosswind landings- extreme!

http://www.youtube.com/watch?v=GHrLB_mlir4

http://www.youtube.com/watch?v=ljOxo0s33sI
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AirWillie6475
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 9:22 am

Quoting SSTsomeday (Thread starter):
the crab landing seems like a less controlled manouver, the touchdown seems violent and precarious, and from what would guess, stressfull to the A/C structure.

You're not supposed to touchdown in a crab angle that could be seriously dangerous especially with fixed gear airplanes. Most commercial airliners have main gears that turn a little 2 or 3 degrees but landing with a crab angle in small planes could cause an uncontrolled situation with aircraft vacating the runway. For me the easiest way is to crab until flaring then add opposite rudder and lower the wing into the wind, I don't like to use slips it just seems like unnecessary work.
 
AirWillie6475
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 9:37 am

 
2H4
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 9:48 am



From the Boeing 747 Flight Crew Training Manual:

"It is not necessary to eliminate the crosswind crab angle prior to touchdown on wet runways. Allowing the airplane to touch down without removing the crab angle will reduce drift toward the downwind side of the runway".


2H4


Intentionally Left Blank
 
boeingfixer
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 11:52 am

Quoting AirWillie6475 (Reply 4):
Most commercial airliners have main gears that turn a little 2 or 3 degrees but landing with a crab angle in small planes could cause an uncontrolled situation with aircraft vacating the runway.

Sorry but the main gear is fixed in position and doesn't turn 2 or 3 degrees. You have a huge problem if it does. The only aircraft that I know of that has castoring gear for crosswind landings is the B-52.

Standard procedure for large commercial aircraft, ig. 737 and larger, is to carry out the approach in the crab configuration and de-crab during the flare.

Cheers,

John
Cheers, John YYC
 
zarniwoop
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 12:18 pm

A long discussion on this topic here:
RE: Crabbed Landing (by Sabenaboy Feb 10 2006 in Tech Ops)
 
sstsomeday
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 6:31 pm

Quoting BoeingFixer (Reply 7):
Standard procedure for large commercial aircraft, ig. 737 and larger, is to carry out the approach in the crab configuration and de-crab during the flare.

This is what I would expect. But some of these crosswind landings we've seen video of shows the A/C landing in the crab position (diagonal to the runway.) So I'm surmising that such landings are incorrect. (except perhaps on wet runways for some A/C)

What I'm gleaning from all your posts is that it's desirable to recover from the crab approach on flare and land with the londitudinal axis parallel to the runway, one wing dipped and opposite rudder as needed.
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PhilSquares
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 6:38 pm

Quoting AirWillie6475 (Reply 4):
Most commercial airliners have main gears that turn a little 2 or 3 degrees

Care to name just one?????

The landing really depends on pilot preference. In the 744, I find it's easier to decrab in the flare and use aileron and rudder to keep the nose tracking straight. Depending on the velocity of the crosswing, even a combination of both techniques can be used. I really prefer to avoid a fully crabbed landing just due to passenger comfort.
Fly fast, live slow
 
ferrypilot
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 8:22 pm

This is my preferred method. ...I start the approach by maintaining a crab angle into the wind (with my wings level) and I continue like this all the way down until I have levelled the aircraft a few feet above the runway. Then I immediately kick it straight with the rudder whilst simultaneously starting to lower the into wind wing with the ailerons as necessary to exactly maintain the runway centre line. During this process I think in terms of quite literally winding the into wind wheel down onto the ground and which almost always results in a smooth contact. ...To the extent that I believe that I actually grease a higher percentage of my landings on one wheel than I do on two.
 
CosmicCruiser
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 9:36 pm

We usually kick out the crab into the slip anywhere from 200' to 400' depending on wind. I would never try to straighten it out in the flare unless the wind was slight. Unless you're right on you could get a downwind drift which reminds me of a particular MD-10 accident. My co. is pretty strict about having it lined up with zero drift. This holds true for all our jets. I spoke to a UAL guy in Narita once who said the same as PhilSquares in that they would just use their preference but the 747 is the only transport cat jet I know that's designed to land in a crab. Anyone know anymore? Don't list B-52 or any with castoring mains. Heck I remember flying a Beech-18 years ago that a mod that allowed the main gear to swivel on x-wind ldgs. I tried never to use it and on t/o if you had any yaw that swiveled the gear then you couldn't retract the gear till they were straight which meant a touch and go!
 
2H4
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 9:48 pm




Quoting CosmicCruiser (Reply 12):
on t/o if you had any yaw that swiveled the gear then you couldn't retract the gear till they were straight

Bad news if you combine that situation with an engine failure shortly after liftoff, eh?


2H4


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CosmicCruiser
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Mar 08, 2007 10:28 pm

Quoting 2H4 (Reply 13):
Bad news if you combine that situation with an engine failure shortly after liftoff, eh?

Thank goodness I never thought about tha. It had an amber light, best I remember, that indicated the gear wasn't straight. >CC
 
Lemurs
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RE: Crosswind Crab Landing VS Lowering One Wing?

Fri Mar 09, 2007 2:22 am

Makes you wonder what your Average Joe in row 35A on one of those 777's would be thinking as he stares right down the centerline of the runway they're about to land on out his window at the back of the plane. "Uhm, if I'm looking at the runway, what is the pilot looking at?" Got to be a fun experience for pax who aren't pilots, don't fly into weather much, or don't read A.net.  Wink
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AJ
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RE: Crosswind Crab Landing VS Lowering One Wing?

Fri Mar 09, 2007 10:30 am

Quoting PhilSquares (Reply 10):
Quoting AirWillie6475 (Reply 4):
Most commercial airliners have main gears that turn a little 2 or 3 degrees

Care to name just one?????

The Boeing 737! Funny little buggers to follow around on the taxiways as they sit skew depending on which way they turned last!
 
Pihero
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RE: Crosswind Crab Landing VS Lowering One Wing?

Fri Mar 09, 2007 12:05 pm

Quoting CosmicCruiser (Reply 12):
but the 747 is the only transport cat jet I know that's designed to land in a crab

Unfortunately, ALL the airplanes from both A and B are thus designed.
My point is : we've been flying with swept winged airliners since the 707, then the Caravelle, the DC-*,9,the 737,the DC-10, the L-1011, the 767, the 757, the A-300/310...not forgetting the various Fokkers 70and 100, the Jumbolino...all aircraft on which, whatever the x-wind, pilots worthy of the name could land with a well-taught and practiced crab/decrab technique or ( DC-10 and Tristar style ) forward slip.
I'm perfectly at ease with either technique. Not the new generation, now being taught that landing crabbed is the safest technique. The vastly reduced training hours must be the explanation.
Sheesh !
P.S ; contrarily to the existing wisdom, Airbii can be landed using the slip technique. Discovered the idea AND the FBW explanation from an UAL training captain !
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CosmicCruiser
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RE: Crosswind Crab Landing VS Lowering One Wing?

Fri Mar 09, 2007 12:33 pm

Quoting Pihero (Reply 17):
...all aircraft on which, whatever the x-wind, pilots worthy of the name could land with a well-taught and practiced crab/decrab technique or ( DC-10 and Tristar style ) forward slip.

I agree with that statement I just said that there weren't any short of the 747 that would be landed in a crab. Ironically I just spoke to a long time friend that flies a 747-400 in Europe and I posed the question to him. He agreed with kicking it out at the last minute but qualified it with "and sometimes you can really make it nice but if you're not careful it will slide downwind and you may catch an engine". "You don't want to hit in a crab". Like I said if the wind isn't strong I'll wait but if it's strong or gusty I'll get set up early and that's the way it's taught here. After all 200' really isn't that high.

Quoting Pihero (Reply 17):
forward slip.

Thanks I agree completely.
 
ferrypilot
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RE: Crosswind Crab Landing VS Lowering One Wing?

Fri Mar 09, 2007 8:30 pm

Quoting CosmicCruiser (Reply 12):
We usually kick out the crab into the slip anywhere from 200' to 400' depending on wind. I would never try to straighten it out in the flare unless the wind was slight.

Heaviest aircraft I have flown is the Dassault Falcon 20 weighing in at just over 14 tons ..."and therefore I would never presume to recommend any technique to an airline pilot" ...However, I can say that on one occasion out of the more than 3,000 hours I flew on that aircraft type that I was once faced with a 20-30 knot wind 90degrees off the runway. Limit for that 20D model was 25knots and the last of three or four read outs on finals from ATC was 25 knots, so I felt entitled to go ahead and land. ...As described above I maintained the very substantial drift angle (wings level) until I had almost killed the rate of descent late in the flare and then "I kicked the drift off hard with right rudder" and immediately wound the left in to wind wheel down on to the ground. As usual I greased that wheel on running straight and true and maintained the aircraft exactly on the centerline throughout the landing. ...Furthermore I had thoroughly enjoyed myself because xwind landings are one of my favourite amusements.
...In fact the Falcon 20 flight manual recommends the technique that you have described and so I have often seen experienced pilots demonstrating that method. ...Usually waffling down through the flare in quite modest crosswinds and in my opinion failing to demonstrate 100% control over their aircraft.
There is another point as well, ..."I do not like the idea of flying down through windshear with my controls crossed up"
 
pilotaydin
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RE: Crosswind Crab Landing VS Lowering One Wing?

Fri Mar 09, 2007 9:33 pm

i land in a crab AND wing low, if you do JUST wing low on the 737, 7 degrees of bank is all you need to kiss the ground with your CFM 56, so i come in a lil crabbed and a lil wing low, that way when i kick in opposite rudder i dont drift downwind with the crosswind  Wink works every time  Smile
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sstsomeday
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RE: Crosswind Crab Landing VS Lowering One Wing?

Sat Mar 10, 2007 1:25 am

Thanks for all your input. I really appreciate it.

Quoting Pihero (Reply 17):
The vastly reduced training hours must be the explanation.

I was not aware of that. Material for another thread, I guess. But are we talking additional simulator time as compensation, because of how sophisticated simluators are these days? Otherwise, your assetion is disconcerting.
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ZBBYLW
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RE: Crosswind Crab Landing VS Lowering One Wing?

Sat Mar 10, 2007 3:31 am

Quoting HighFlyer9790 (Reply 2):
Each aircraft has a maximum crosswind component. if the crosswind is above that, you MUST divert. of course, each airline varies this according to their SOPs. as expected, and autoland has its own maximums.

With all due respect, Highflyer you do not need to divert the crosswind components in the POH are maximum demonstrated crosswind component, which I believe on smaller aircraft demonstrates landing the aircraft in a 100% crab. I personally have landed a C152 in 20 kts x wind component and one of my instructors from school had landed another C152 in 30 kts of cross wind. As long as you use the wing low (slipping) approach in these situations and do not stress out the A/C all is well. Now landing a tail-wheel a/c is much harder in the cross wind and that is where things get interesting.

Cheers Chris
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sccutler
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RE: Crosswind Crab Landing VS Lowering One Wing?

Wed Mar 28, 2007 12:52 pm

Quoting ZBBYLW (Reply 22):
Quoting HighFlyer9790 (Reply 2):
Each aircraft has a maximum crosswind component. if the crosswind is above that, you MUST divert. of course, each airline varies this according to their SOPs. as expected, and autoland has its own maximums.

With all due respect, Highflyer you do not need to divert the crosswind components in the POH are maximum demonstrated crosswind component, which I believe on smaller aircraft demonstrates landing the aircraft in a 100% crab. I personally have landed a C152 in 20 kts x wind component and one of my instructors from school had landed another C152 in 30 kts of cross wind. As long as you use the wing low (slipping) approach in these situations and do not stress out the A/C all is well. Now landing a tail-wheel a/c is much harder in the cross wind and that is where things get interesting.

Cheers Chris

Agreed; maximum demonstrated crosswind component is not a limitation, it is a statement of the maximum xwind component demonstrated during the certification flight testing of the aircraft. Many aircraft can land in significantly greater crosswinds.

I have landed a Bonanza in a 24G37 knot crosswind with about 75 degree crosswind component- significantly in excess of the Bonanza's "demonstrated" figure. I was primed and ready to go around if needed, and I was blessed with a runway which was both long and wide, which improves the odds. It worked out fine.
...three miles from BRONS, clear for the ILS one five approach...
 
ferrypilot
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RE: Crosswind Crab Landing VS Lowering One Wing?

Thu Apr 05, 2007 8:47 pm

Quoting SCCutler (Reply 23):

Agreed; maximum demonstrated crosswind component is not a limitation, it is a statement of the maximum xwind component demonstrated during the certification flight testing of the aircraft. Many aircraft can land in significantly greater crosswinds.

It is worth bearing in mind that those guys who do the flight testing of aircraft are usually qualified test pilots and imbued with well above average aircraft handling skills.

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