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Old 02-16-2018, 06:23 AM   #11  
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Default Great explanation .

Thank you! That makes perfect sense.
I was thinking the wing would raise due to the yaw at last seccond, but the aerodynamics of a landing a swept wing jet were never explained in our training. You would think it would be worth 30 minutes, or so


Quote:
Originally Posted by 1wife2airlines View Post
Just to be clear, there is no rudder to kick out in the flare, there is a crab angle, in coordinated flight, which must be reduced to runway alignment using rudder for longitudinal correction while using aileron to keep the upwind wing from rising due to the yaw. This crosscontrol in the flare is also be called a slip.
Any aileron input error should be to the excess which would put the upwind gear down earlier than the downwind. Some guys do that on purpose.
I've seen more sideslip to landing sideloads on big jets caused by the guy who wants to fly it like a cub than sideloads by guys who did not decrab enough.
If your airplane does autoland read how it corrects for X-wind.
Even on aircraft designed to land in a crab, such as the T-38, most guys naturally gravitated to a decrab in the flare.
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Old 02-17-2018, 06:06 AM   #12  
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Default ORD RWY 28 C Winds 200 / 19 KT G 27

Nice landing, in my rookie opinion.
What I noticed:

- removed crab as low as possible ; about 5 feet it seemed ?
- still had some crab into wind.
- appeared to touchdown in slight crab, with slight side load.
- straightened nose after touch down.
- kept wings level. ( no chance of wing strike.)

Any thoughts on this one ?


https://www.youtube.com/watch?v=wol0Lh10gOs
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Old 02-17-2018, 06:19 AM   #13  
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Quote:
Originally Posted by Paladin145 View Post
Nice landing, in my rookie opinion.
What I noticed:

- removed crab as low as possible ; about 5 feet it seemed ?
- still had some crab into wind.
- appeared to touchdown in slight crab, with slight side load.
- straightened nose after touch down.
- kept wings level. ( no chance of wing strike.)

Any thoughts on this one ?


https://www.youtube.com/watch?v=wol0Lh10gOs
technique is technique but I don’t know anyone who lands in the crab except by accident.
This guys downwind wing definitely dips for lack of ailerons control.
There is plenty of aileron control and no need to side load these airplanes in normal ops.

What isn’t technique is momentum.
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Old 02-17-2018, 07:01 AM   #14  
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Quote:
Originally Posted by WesternSkies View Post
technique is technique but I don’t know anyone who lands in the crab except by accident.
FYI, 777F cross-wind limits are 38 knots. With a x-wind component in excess of 28 knots, it's not possible to get to zero crab and the aircraft must be landed while crabbed.

Also, the aircraft is actually certified to land up to the maximum crosswind limits in a full crab (not my first choice of technique, personally). While not recommended on a dry runway in very strong x-winds, this is actually may be desirable with a slippery runway.
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Old 02-17-2018, 07:04 AM   #15  
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Quote:
Originally Posted by Paladin145 View Post
Nice landing, in my rookie opinion.
What I noticed:

- removed crab as low as possible ; about 5 feet it seemed ?
- still had some crab into wind.
- appeared to touchdown in slight crab, with slight side load.
- straightened nose after touch down.
- kept wings level. ( no chance of wing strike.)

Any thoughts on this one ?


https://www.youtube.com/watch?v=wol0Lh10gOs
Pilot didn’t fully decrab; the right (downwind) wing dropped as the gear “took out the crab” the hard way. The rotation on the pivot point caused the wing to drop. It’s hard for a pilot to input aileron to stop the wingtip drop caused this way, as the rotation about the downwind gear is sudden and concurrent with touchdown. You are being, to some degree, being “tossed” in your seat at the same time as the wingtip moves. This is how downwind tips get stuck.

Better to land with some crab on than overdo the decrab input and land in a drift with the nose pointed a bit downwind.
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Old 02-17-2018, 07:20 AM   #16  
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Quote:
Originally Posted by Adlerdriver View Post
FYI, 777F cross-wind limits are 38 knots. With a x-wind component in excess of 28 knots, it's not possible to get to zero crab and the aircraft must be landed while crabbed.

Also, the aircraft is actually certified to land up to the maximum crosswind limits in a full crab (not my first choice of technique, personally). While not recommended on a dry runway in very strong x-winds, this is actually may be desirable with a slippery runway.
Interesting. Makes me think of that Boeing x-wind cert video.
For clarity in my previous post I was speaking of the CRJ series specifically, I hope I wouldn’t be such a jack wagon to speak in as general terms as it looked.
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Old 02-17-2018, 07:59 AM   #17  
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Default Good catch on noticing the downwind wing

I was focused on the upwing wing, and crab angle.


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Originally Posted by galaxy flyer View Post
Pilot didn’t fully decrab; the right (downwind) wing dropped as the gear “took out the crab” the hard way. The rotation on the pivot point caused the wing to drop. It’s hard for a pilot to input aileron to stop the wingtip drop caused this way, as the rotation about the downwind gear is sudden and concurrent with touchdown. You are being, to some degree, being “tossed” in your seat at the same time as the wingtip moves. This is how downwind tips get stuck.

Better to land with some crab on than overdo the decrab input and land in a drift with the nose pointed a bit downwind.
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Old 02-17-2018, 12:30 PM   #18  
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I’ve done investigations on strikes.

GF
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Old 02-17-2018, 01:48 PM   #19  
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CRJ. Crab until just below 10’ RA, then kick the rudder over. The more rudder input you apply, the faster the advancing wing will produce lift. If you don’t use aileron correction, a wing strike could occur.
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Old 02-17-2018, 02:11 PM   #20  
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Quick story on why “kick” is a bad word I don’t use.

Windy day going into Yakima in an empty C-5 which is a kite. 40* crosswind nearing the limits for conditions, IIRC about 28 knots of left crosswind component, 32.5* was the charted limit. Newish pilot flying, we had a discussion on crosswind techniques. He was ready and geared up. Nicely flown approach off the VOR, good weather except for winds. I’m in the right seat, watching, hands off the controls, feet resting on the pedals. He’s nicely stable and good air speed control going thru 50’, I call “20”, and my right pedal disappears under my foot. Oh boy! Nose swings thru the centerline, I grab my set of throttles and, say, “MY AIRPLANE”. As the thrust kicked in we were at the right hand edge of the runway and I remembering wondering if we’d touch. Off we went, thanks to GE and a light airplane.

Point being, just squeeze enough rudder to align the fuselage with the runway, think upwind aileron to hold the wings level, which will probably have set 2*-3* of bank into the wind. It’s poetry, not prose.

GF
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