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Elixir
20th May 2006, 16:12
I am new to jet flying and just trying to find the best way to land a 737 in a crosswind - specifically 300 series.

When is the best time for pushing off the drift in relation to the flare? A couple of times in strong crosswind I have pushed off drift before flaring and have found myself drifting downwind. I ask because I recently saw a video of a 747 landing in a crosswind - its main wheels touched down while the aircraft was still pointing into wind and then it aligned itself. Are there different methods depending on the size of the jet?

Any advice much appreciated as this is what I find most difficult. Thanks

Dave Spart
20th May 2006, 16:35
Sounds to me like you're straightening her up a bit high. De-crab during the flare and use plenty of into wind aileron. You *might* wish to touch down just a fraction upwind and with a smidgen of wing down too, just for mum.

It does take time to get consistently good at crosswind landings, as the old saying goes, there ain't no substitute for experience!

Pilot Pete
20th May 2006, 20:09
If you kick the drift off before the flare, you will need to put the into wind wing down and land on the upwind maingear first, otherwise you will get the drift you mention. Otherwise, kick the drift off as you flare and still stop the drift with into wind aileron. As Dave says, it just takes plenty of exposure! Make sure you don't shy away from having a go if offered the choice of sectors and TELL the captain you are not overly experienced BEFORE you make the approach. That way he will feel more comfortable with things not being perfect whilst you practice and will be even more ready to 'offer assistance' should it be required!;) Make sure you ask for feedback afterwards too, as he may be able to help you pinpoint why something didn't go as planned. Most good captains are willing to offer advice if asked, but many won't offer it unless you DO ask, unless of course it is a training flight!

PP

Charles Darwin
20th May 2006, 20:32
...and if you can afford it (runway permitting) use only 30 flaps in strong crosswind, not 40. Much better!

fireflybob
21st May 2006, 09:01
Good crosswind landings using the crab technique are, to an extent, a question of "timing" - ie when to straighten the aircraft with rudder prior to touchdown.

Pilot Pete gives some good tips but, personally, I don't like the terminology "kick off drift" and prefer "straighten the aircraft (with the runway)" with a thoughtful application of rudder. As has been stated the further effect of rudder is roll, so as you apply rudder you are simultaneously applying into wind aileron. If you are going to make any mistakes apply a bit too much aileron, favouring touchdown on the upwind gear first.

Also make sure you do not arrive at the 50 ft point with excess speed (obviously apply the recommended increments to Vref) otherwise you will float making judgement of when to apply rudder more challenging and do not go in for an extended flare - better to land slightly "flatter" than usual so you have more control as to when the aircraft touches down.

I think we also have to define what we mean by a crosswind which brings to mind a funny story from years ago! New FO was landing B737 at BHX with training captain and did what only could be described as a "firm arrival". On the debrief TC asks trainee to comment on his landing. He then went on to describe the cross wind landing technique - they were landing on RW 33 and the wind was 240/3 kt! Only 3 kts of crosswind component and he had the concept that this required a huge change of technique!!

So make sure you get the approach right too - very often with limiting crosswind components the drift looks fairly horrendous when at a few hundred feet but much of this drift disappears as you get close to the ground.

From a training perspective, limiting crosswind landings are not specifically taught unless your friendly TC teaches it in the sim but sims do not always trully represent the real world but its a good place to learn the correct techniques.

When I was on the B 707 with a major state carrier in the 1970s, crosswind landings were specifically part of the command course and they used to deliberately find somewhere in Europe where the wind was on (if not above) the max crosswind component to practise same. The B 707-436 did not have a series yaw damper so you had to land with the yaw damper disengaged and if you got any roll on during the flare it was easy to scrape the outer pod on the ground - Good Game, Good Game!!

Hope this helps!

gonso
21st May 2006, 10:04
Especially on very strong xwinds (30+) I tend to align with the runway only by 50%. For example, Ig my crab is 20 degrees, I touch down with 10 degrees. It makes the whole maneuver a little bit more comfortable. Kicking off 20+degrees at the last 20 feet causes quite a bit of roll. Touching down with 10 degrees crab is perfectly OK.

Permafrost_ATPL
21st May 2006, 10:50
Does Boeing give a max safe crab angle for touchdown? And would the limiting factor be the tyres or the gear assembly?

Talking of crosswing landings...
http://www.metacafe.com/watch/39256/crosswinds/

i'm sure a lot of you have seen it before, but it's worth a second look. From Boeing's testing footage. No idea what the spanish comments mean!

P

gonso
21st May 2006, 15:29
Mr Boeing (his lawyers to be exact), state in the FCTM that the crab that is caused by max landing crosswind component is acceptable for touchdown. Without de-crabing at all.

Pilot Pete
21st May 2006, 16:59
I don't like the terminology "kick off drift" and prefer "straighten the aircraft (with the runway)" with a thoughtful application of rudder. That's why I'm not a trainer;) , just a line captain who applies the technique you mention, but doesn't perhaps explain it as well as it could have been explained!:ok:

PP

Elixir
21st May 2006, 18:13
Thanks - lots of great advice! Its the view from the flightdeck in the last couple of hundred feet that makes me feel I've got way too much drift on, which I guess is why I try to straighten up too early. So hoping that after a few more landings I'll get the hang of it...:ok:

Pilot Pete
21st May 2006, 19:13
The problem you get if you straighten up too early (say at a couple of hundred feet), is that the wind of course backs and decreases as you get over the runway, so your adjustment at 200' is now not correct at touchdown! I was once taught to do this by a, how shall we put it, not overly fantastic training captain! This lead to trying to adjust the rudder and aileron really late on and just made things worse!

When you make the adjustment to the rudder to line the aircraft up with the runway, hold it there. Do not be tempted to 'fiddle with it' as you will get all out of shape. Make the rest of your adjustments using aileron alone, in effect with a new datum (your wing down position), adding more if you are losing the centre line downwind and rolling some aileron off if you are losing the centre line upwind. In both cases, when you have the centre line back, adjust aileron again to hold it there.

What you really want are strong crosswinds with no gust for practice. It won't take long to get them right, but if it is gusty, or a crossind that is rolling over hangars or terminal buildings (like Manchester 24R) then it is not easy to learn the correct base line technique as there is so much else going on!!

Have fun.

PP

john_tullamarine
22nd May 2006, 00:18
I ended up with a fairly simple, but quite repeatable, techique on the 733 for moderate to strong crosswind ... and near always ended up with a nice touchdown .. and not much pilot anxiety or sweat.

(a) correct the approach drift angle at a height appropriate to the crosswind .. moderate around 100 ft .. strong around 200 ft

(b) in association with (a) feed in (more or less simultaneously) enough

(i) aileron to establish sideslip sufficient to maintain centreline track
(ii) rudder to keep aligned with centreline
(ii) elevator to correct the lift delta associated with the bank .. typically 1-2 degrees pitch. I've seen a lot of pilots (especially coming onto the aircraft) who don't increase pitch and that usually causes the whole thing to go a bit pear-shaped.

(c) fly it to the flare like any average Piper Cherokee. Although the "feeling" during this last part of the approach is a bit strange to the seat of the pants, it allows the pilot adequate time to adjust control inputs to the conditions so that the aircraft enters the flare under fairly tight pilot control.

(d) normal flare and touchdown, feeding in aileron as the speed reduces and rudder to suit tracking along the runway.

This technique appeared to work very well with typical crosswinds (20-odd kts) and, on those occasions where I had strong crosswinds, I don't recall any undue problem with the final approach, flare and touchdown ... Obviously, the description above is the underlying thrust of the thing and, overlaid on this, is a pattern of control perturbations to account for the variable nature of the typical gusting crosswind .. just a matter of doing a bit of practice until you get on top of the basics .. and, if that means requesting the occasional crosswind for practice, so be it.

Other than for light, steady crosswinds, I never liked the "doing it all during the flare" technique .. this is a very dynamic manoeuvre and it doesn't make sense loading up the skill requirements when there is a much easier and consistent way of doing it... maybe I just wasn't skilled enough to do it the hard way ?

TomConard
22nd May 2006, 02:21
Elixir:


John's 'technique' is correct. In fact, it is almost ver batim the SOP of my old company. :> :> :> :>

Which brings me to my question. What is YOUR company's SOP with regard to this issue?

Have fun with the 737. It's a wonderful aircraft. You'll love it.


Tom

xetroV
22nd May 2006, 14:38
Mr Boeing (his lawyers to be exact), state in the FCTM that the crab that is caused by max landing crosswind component is acceptable for touchdown. Without de-crabing at all.
The FCTM also states:
If the crew elects to fly the sideslip to touchdown, it may be necessary to add a crab during strong crosswinds.
It then refers to the landing crosswind guidelines table, which includes the following note:
Sideslip only (zero crab) landings are not recommended with crosswinds in excess of 17 knots at flaps 15, 20 knots at flaps 30, or 23 knots at flaps 40. This recommendation ensures adequate ground clearance and is based on maintaining adequate control margin.
For NG's with winglets, the zero crab landing crosswinds are further reduced by 2 knots. Roughtly translated for normal conditions: do not try to fully decrab if the crosswind exceeds 20kts or you may end up damaging your flap fairing or engine nacelle. Something worth to consider, especially if you favour wing low landings.

Concerning my own landing technique, I personally prefer decrabbing during the flare. This is probably because that's the technique my instructor taught me back in my PPL days and it's suited me ever since. It is a dynamic manoeuvre alright, but very much controllable if you apply your corrections with care. Descending through 500 feet or so (I'd say 1000 for a widebody), start aiming slightly upwind of the centerline/localizer. During the flare gently (!) apply rudder to align (or at least: start aligning) the nose parallel to the centerline, and use ailerons to arrest the drift - normally works like a charm... for me.

The 737 rudder is very effective so you really must be careful not to overcorrect. Keeping in mind Boeing's recommendations I'd rather land with the nose slightly facing to the upwind side than give too much rudder input with the nose ending up pointing downwind. Notice that if you land with a slight crab angle it is actually pretty easy to further align the nose with the centerline during the transition to nosewheel touchdown, especially if you land the nosewheel gently, like it is done by the Boeing test pilots in the first 777 landing from the videoclip mentioned by Permafrost.

Elixir, in the end I think you need to find out what works best for you, and that obviously requires experience. The 737 FCTM mentions de-crabbing during flare, touchdown in crab, and sideslip (wing low) techniques as valid x-wind landing techniques, but leaves room for the pilot to decide what works best. Luckily, the SOPs of my company allow some leeway too (in both meanings of the word)... although landing in crab at max. crosswind will surely raise some eyebrows. :}