mirrodie
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777 Landing Observation

Fri Dec 23, 2005 6:23 am

I recently flew and posted about it in the trip reports section. I was my first trip on a 777,

The flight left many positive impressions on me but hte landing was the best.

As we landed in LHR, (and we sat directly above the wheels), that plane came down on one set of bogies and then the other. That thing was sashayed left and right to get on the runway. Pretty wild fishtailing feeling. And since we were sitting above the wheels, I would think the sensation was greater in other parts of the plane.

ON the return, we saw in first, but I felt the same effects of a sort of back and forth setlting of hte plane as the plane touched down.

Would you say that is a function of the aircraft itself or simply a crazy crosswind landing?


And since we are to fly the A 340 in July, we'll see how that compares!
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julesmusician
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RE: 777 Landing Observation

Fri Dec 23, 2005 6:30 am

Did you check the historical METAR on LHR to see if it was suffering cross winds? That is the first thing to do after a landing like that  Smile
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bri2k1
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RE: 777 Landing Observation

Fri Dec 23, 2005 6:48 am

You'd have to also know which runway you landed on to see if the prevailing winds at the time of landing were crosswise to the runway.

Airliners, especially those with enormous engines mounted under very long wings, do not use the wing-low method of crosswind landing. They maintain the crab angle all the way until the first (downwind) main bogey touches, just slightly lower than the other. Then, rudder is used to align the fuselage with the runway, and the rest of the wheels are set down. It makes for some really smoky pictures; search for any video of any landing at Kai Tak.

I've experienced every type of landing I can think of (except an aborted one) aboard a 777, and also been privelged to fly the United Airlines 777 full-motion simulator. My best guess is you experienced a normal crosswind landing. The pilots of a 777 will be among the most experienced in a given airline, so lack of technique is probably not the case. However, I've been on a 777-200 in extremely bumpy descents, being pitched and rolled violently about, and been dreading the rough touchdown, when the actual landing was so smooth (one particular time at ORD) that you could barely tell when the wheels hit the pavement.
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Starlionblue
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RE: 777 Landing Observation

Fri Dec 23, 2005 9:05 am

Quoting Mirrodie (Thread starter):

As we landed in LHR, (and we sat directly above the wheels), that plane came down on one set of bogies and then the other. That thing was sashayed left and right to get on the runway. Pretty wild fishtailing feeling. And since we were sitting above the wheels, I would think the sensation was greater in other parts of the plane.

As has been said, this is fairly typical of crosswind landings in the 777. I'm not a 777 pilot but I have done about 35 flights on the AA 772s this year (and about 20 last year) so I have some experience Big grin
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mirrodie
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RE: 777 Landing Observation

Fri Dec 23, 2005 9:20 am

Quoting Julesmusician (Reply 1):
Did you check the historical METAR on LHR to see if it was suffering cross winds? That is the first thing to do after a landing like that

well, perhaps I can leave that up to you. as I'd have no clue how too! But the dates in question were:

LHR on 6 December, 2005 at 2030 on 27 L and
JFK on 17 December 2005 at 1930 on 31 R

And yes, I think you are on it, I think it was a crosswond landing we got. I mean, it play it in slow motion, it was like one set of wheels hit. (In fact, I almost feel as if we sensed each pair of side my side wheels touch), then the other bogie touched, then a sort of shimmy and sashaying in order to center on the runway.

I hope you can tell me more regarding the winds those days, but you are probably 100% correct Big grin
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PhilSquares
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RE: 777 Landing Observation

Fri Dec 23, 2005 9:23 am

Quoting Bri2k1 (Reply 2):
Airliners, especially those with enormous engines mounted under very long wings, do not use the wing-low method of crosswind landing. They maintain the crab angle all the way until the first (downwind) main bogey touches, just slightly lower than the other. Then, rudder is used to align the fuselage with the runway, and the rest of the wheels are set down. It makes for some really smoky pictures; search for any video of any landing at Kai Tak.

That's not quite true. There are several techniques for crosswind landings. Landing in a crab is certainly an acceptable technique for Boeings, but it really provides for a very uncomfortable touchdown.

I think most pilots use a technique where someplace around 100' or so they start to use rudder to align the nose and opposite aileron to keep the aircraft flying straight, sort of cross controlling. That technique provides for a much smoother touch down.

As far at the 777 landing as described, I really think it was just a function of the crosswind present at the time, nothing more.
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bri2k1
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RE: 777 Landing Observation

Fri Dec 23, 2005 9:39 am

Good point, I used more of a generalization than I should have. I believe most airliners will produce very uncomfortable sensations for passengers in an extended sideslip, and may even induce some oscillations or vibrations in some types. I agree most landings in any aircraft are a combination of every technique available to reach a safe, comfortable touchdown.

Now, a question for 777 pilots: What technique does the autoland use? My guess is it's more of a crab than a cross-controlled sideslip, but that's just a guess. I would think the problem with the sideslip for wing-mounted engined aircraft is that the stronger the crosswind, the more rudder required to align the nose, and the more opposite aileron required to maintain the track, but there's not too much clearance under the upwind engine.

And, I found the photos from Kai Tak that I was looking for:


View Large View Medium
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Photo © Colin Parker
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Photo © Colin Parker



View Large View Medium
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Photo © Colin Parker
View Large View Medium
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Photo © Colin Parker

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PhilSquares
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RE: 777 Landing Observation

Fri Dec 23, 2005 11:24 am

Quoting Bri2k1 (Reply 6):
I believe most airliners will produce very uncomfortable sensations for passengers in an extended sideslip, and may even induce some oscillations or vibrations in some types.

Actually, I think landing in a crab would produce the most uncomfortable results! It's pretty uncomfortable to land 30 degrees of runway heading and then whip around so you're tracking straight down the runway!

Quoting Bri2k1 (Reply 6):
would think the problem with the sideslip for wing-mounted engined aircraft is that the stronger the crosswind, the more rudder required to align the nose, and the more opposite aileron required to maintain the track, but there's not too much clearance under the upwind engine.

As long as you land with the wings level, there's no problem. On the 744 you can land like that right up to the demonstrated limits.
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2H4
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RE: 777 Landing Observation

Fri Dec 23, 2005 11:57 am




Quoting PhilSquares (Reply 7):
On the 744 you can land like that right up to the demonstrated limits.



The loads the landing gear must sustain during landings like this must be absolutely incredible.




2H4


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bri2k1
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RE: 777 Landing Observation

Fri Dec 23, 2005 12:49 pm

Quoting PhilSquares (Reply 7):
It's pretty uncomfortable to land 30 degrees of runway heading and then whip around

I can imagine. If the winds were strong, could you arrest the sink rate right as the wheels touch down, so you don't whip around, but line it up slowly?

I'm just trying to perfect my crosswind landing in the C172, which sustains approximately no sideloads on the gear, so I'm trying to transition from the crab in the final descent to the wing-low method just above the runway, too...so this is very interesting to me  Smile
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PhilSquares
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RE: 777 Landing Observation

Fri Dec 23, 2005 2:16 pm

Quoting Bri2k1 (Reply 9):
I can imagine. If the winds were strong, could you arrest the sink rate right as the wheels touch down, so you don't whip around, but line it up slowly?

Well, that's the nice thing about using the rudder and opposite aileron technique. To be honest, that technique takes more experience and feel. Landing in a crab is pretty much a "no brainer". All the aircraft I flew in the military were landed like that. However, if you're interested in passenger comfort, then the above techniqaue is the way I think it should be done.
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Grbld
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RE: 777 Landing Observation

Fri Dec 23, 2005 7:11 pm

Quoting Bri2k1 (Reply 6):
What technique does the autoland use?

If it's anything like the 757/767 (and I think 744 as well, Phil?) autoland, then the aircraft will start to put in rudder and align the aircraft with the runway after 1500ft above the ground. So that way, it will make an autoland, cross-controlled and wing-low but perfectly aligned with the runway.

Remember though that autolands are subject to strict crosswind limits, so you wouldn't do an autoland with such strong crosswinds that you'd risk a pod strike by flying wing-low.

This method is extremely precise and comfortable and as such, good to use by the autopilot. "Kicking the rudder" and straightening out the aircraft during the flare or touchdown is a much less precise procedure and depends on flying skill more than the autopilot can do. If you do this technique in a wrong manner, you can end up drifting off the centerline and making a mess of the landing.

That said, I think that I usually do the straightening out during the flare on the 737, whereas I preferred the wing-low method on the 757. Maybe it's because I know how low the engines are to the ground on the 737.

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HAWK21M
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RE: 777 Landing Observation

Sat Dec 24, 2005 12:19 am

Quoting 2H4 (Reply 8):
The loads the landing gear must sustain during landings like this must be absolutely incredible

There was a Documentry on MLGs illustrating this landing on Discovery channel.
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jeffry747
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RE: 777 Landing Observation

Sat Dec 24, 2005 8:29 pm

Quoting 2H4 (Reply 8):
The loads the landing gear must sustain during landings like this must be absolutely incredible.

According to the captions, this 744 shredded some tires.
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Mr.BA
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RE: 777 Landing Observation

Fri Dec 30, 2005 9:00 am

If there is a strong gusting crosswind, wouldn't it be very difficult to coordinate the rudder with the ailerons to point the nose down the centreline and at the same time ensuring the wings to be level? I would think this method would only be pretty much easier when the crosswind is rather stable or am I wrong?
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DColeMAN
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RE: 777 Landing Observation

Fri Dec 30, 2005 10:15 am

Quoting PhilSquares (Reply 5):
I think most pilots use a technique where someplace around 100' or so they start to use rudder to align the nose and opposite aileron to keep the aircraft flying straight, sort of cross controlling. That technique provides for a much smoother touch down.

A perfect demonstration of this landing technique -

http://www.flightlevel350.com/viewer.php?id=1568

As a matter of fact I've just noticed it's actually an SQ 744 and the technique you suggested Mike is very similar to the video footage.... You weren't the PF by any chance were you? 

Dale

[Edited 2005-12-30 02:17:36]
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Cruiser
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RE: 777 Landing Observation

Fri Dec 30, 2005 10:23 am

I have just uploaded a great video that I have found elsewhere on the net. I wish I could give you the original source, but unfortunately, I only have the .wmv file.

It is a video of various 777 landings during testing, with a 747 landing thrown in there too. The last 777 landing is crazy!!!

http://stw.ryerson.ca/~jbainton/Pics/Boeing777-xwindcert.wmv

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Jetlagged
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RE: 777 Landing Observation

Fri Dec 30, 2005 11:08 am

Quoting Grbld (Reply 11):
If it's anything like the 757/767 (and I think 744 as well, Phil?) autoland, then the aircraft will start to put in rudder and align the aircraft with the runway after 1500ft above the ground.

I don't know about the 744, but the 742 autoland maintains the crab angle until the last few feet before touchdown. From memory, kick off drift begins at 2 feet (main gear wheel height above ground).

Much as I respect the various comments above, I have never experienced a cross wind landing in an airliner where the pilot has done anything else except crab in and kick off drift just before touchdown. Watching pilots conduct crosswind approaches in simulators, I have never seen the wing low technique used. I'm not saying it does not happen, but by the law of averages I would have expected to notice it used at least occasionally.
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CX Flyboy
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RE: 777 Landing Observation

Fri Dec 30, 2005 11:51 am

One thing about the 777, if you land with a little bit of crab, you get the sensation that you describe. The aircraft wobbles from side to side for a bit after touchdown. It is actually smoother to land with a crab in 10kts or more of crosswind that it is to land with 5kts and not notice the crab enough to correct it.
 
bri2k1
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RE: 777 Landing Observation

Fri Dec 30, 2005 2:15 pm

Quoting Mr.BA (Reply 14):
If there is a strong gusting crosswind, wouldn't it be very difficult to coordinate the rudder with the ailerons to point the nose down the centreline and at the same time ensuring the wings to be level?

Ah, yes, you've described the fun of crosswind landings. But you can't do both. You can point the nose at the centerline and keep the wings level, but if the fuselage is lined up with the runway, and the nose isn't, you must lower the upwind wing. Then, a component of vertical lift is directed into the wind, which keeps your ground track aligned with the runway. The rudder keeps the nose pointing the same direction you're flying. It's aileron into the wind, but rudder away from it. This type of cross-controlled input is unnatural at first. And, when the wind is not continous, but gusting (as most winds are), you have to be continously making small (or sometimes large) control inputs to keep everything where you want it.
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