737 Crosswind takeoff

[Olendirk]

Guys,

some questions:

1. How to do the proper takeoff? How much defelction and how much rudder? when do we release the crossed controls after airborne?

2.According flight director? can we follow the fd initially? the fd doesnt correct for crosswind right? so look through?

thanks for help!

od

[BOAC]

http://www.pprune.org/forums/showthr...sswind+aileron

http://www.pprune.org/forums/showthr...sswind+aileron

and other items from 'search'.

After take-off, the a/c should be pointed to correct for drift, so, until you can use 'heading' with the corrected heading or LNAV mode, 'look through' is correct.

[RYR-738-JOCKEY]

Rudder: Enough to keep you on the centre-line. Aileron: Initially, no more than 6', because that will raise the spoilers. Then at rotation, add aileron to keep wings level. Fd's: Don't follow the vertical bar, cause it commands heading. Just release rudder+aileron just after lift-off and follow your track on the ND.

[Kit d'Rection KG]

Errr, read the Flight Crew Training Manual.

Regarding RYR's post above, the spoilers have practically no effect on the ground roll (when you say they should not be used) and a slight effect during the V2 plus a bit climb (where you say they may be used to keep the wings level). Rethink required perhaps?

[Rainboe]

Quite right Kit! There is this myth that a little spoiler upfloat on the ground is 'a bad thing' Nonsense! Anybody who flies Boeings know that speedbrakes below 250 kts are pretty useless. A bit of spoiler upfloat provides negligible drag.

In a strong crosswind (>20 kts), you are likely to need about 4 or more of those divisions on the control boss. This is going to give you about 25 degrees or more of aileron. Put it there at the start of the roll and leave it there until after lift off! Don't take it off when you get airborne. I constantly see people remove it when airborne- as the crosswind hits them, the into wind wing rolls up, and back it comes on, twice the deflection. Just leave it on, let the aeroplane settle as it yaws, then just fly the aeroplane wings level. A good guide is what was used on the 747 and works well for the 737- set 1 division aileron per 5kts crosswind, and leave it. Try it.

Another self imposed myth that seems to be pervading our airline now amongst the copilots is 'we must slow to 250kts maximum below 10,000'!'. I ask why? Where did that come from? The response is 'because of birds!' I have to positively say 'to hell with the birds, we're late! There is no speed limit unless you have a broken windscreen! I'm up here, and my cold beer is down there- why are you keeping me from it?'

[MrBernoulli]

Initially, no more than 6', because that will raise the spoilers.

Wrong! Mr Boeing has taken the use of the spoilers into his performance calculations for takeoff. Use as much roll control as you need to keep the wings level during a crosswind takeoff. The 'negligible drag' comments are also red herrings - whilst there might be some drag the major factor being considered is actually the generation of lift! But as I said, this had already been accounted for in the aircraft's certification.

[Artie Fufkin]

Possibly hijacking the thread somewhat, but here goes;

As Rainboe says once airborne, the flight directors give "wings level" in the B737. Presumably in the airbus, you get something else as I remember last winter getting stuck at the holding point on 09R at LFPG and had to sit and watch about 8 heavys takeoff. All the airbuses took off and tracked the runway QFU and all the boeings started drifting off towards 09L.

The question is, how does this apparent difference affect parralel runway operations - I wouldn't personally have fancied going around off 09L in an airbus when a Boeing was taking off from 09R.

Or have I missed something?

[Centaurus]

Wrong! Mr Boeing has taken the use of the spoilers into his performance calculations for takeoff

It all depends how much spoiler is applied. The operation of spoilers creates drag. Drag increases as the square of the velocity. That is why there is a marked deceleration immediately on touch down as spoilers are automatically deployed. Same principle applies at higher speed during take off run. Nearing rotation speed spoiler operation drag is significant if too much applied. Boeing stated in an earlier edition of the FCTM that I have, that the take off distance increases with inappropriate use of aileron/spoiler use during a cross wind take off. This in turn makes V1 useless.

[SuperRanger]

i dont know if the rest of you noticed this or not. for me, the 'correct' amount of ailerons would be just sufficient to offset the rudder input! i.e. if you have the correct amount of ailerons, you should require minimal rudder input!? at least that works for me.

and if you DO NOT hold the ailerons till airborne, your wings are bound to 'dip' just at liftoff. i guess, these will be more significant on the larger boeings.

SR

[Rainboe]

the 'correct' amount of ailerons would be just sufficient to offset the rudder input!

Don't agree with this at all. There are 2 factors affecting you on a crosswind take-off:
1- Lifting effect of the upwind wing
2- Weathercocking into wind effect of the side force on the fin.

Both quite independant. Rudder does not stop wing lifting.
You counter with:
1- into wind aileron
2- side force with rudder downwind

So you don't end up wrestling with controls whilst wheels are on the ground, I think you are best just leaving aileron fixed at your estmated setting, and keep tracking down the runway centreline with rudder. Whilst you are doing that, just feel for the upwind wing lifting, and hold it down with more aileron if need be. The lifting effect will probably reach its peak near rotate. When you lift off, you will instantaneously be in yaw in the air. You had better have your aileron on then, because that is when the wing will lift- and that is just when people tend to freak that they are airborne with all this aileron on! So off comes the aileron, the aeroplane tips downwind, then on comes up to double the aileron to get tyhe downwind wing back up. I see it all the time, then tell the copilot how much aileron he had to put on because he didn't listen to daddy!

Olendirk- try it, and report back. If you take that aileron off at take-off, try and see how much you then have to put on to level the wings. If it is not double what you would have had on the roll, I'd be surprised.

I think in threads like this, one should say what experience one has. 34 years on jets, nearly 20,000 hours. 18 years 747, 10 years 737, 6 years VC10.

(Heavens- we haven't even got into crosswind landings yet!)

[RYR-738-JOCKEY]

Uh...guys. The effect of raising the speedbrakes is that of changing your Vmcg, due to the yaw. The drag will be negligible.
I'm not talking about a 5 knot x-wind T/O, but a procedure that will keep you safe when taking off in max x-wind, V1 close to Vmcg, and then add an eng fail on top (critical engine, that is).
In our FCTM it says exactly that. Use a maximum of 6' aileron deflection during ground roll. Keep wings level during rotation.

[PantLoad]

Well, back in the brown shoe days....

I remember when I was wet behind the ears, flying with a crusty old captain who had more time in various aircraft than I had in a "T" shirt...(This is pushing 35 years ago.)...He told me, with regard to flying the 727 and the 737, 'It flies just like a Cub. Fly it just like a Cub.'

Hell, he was right...it's just an airplane...nothing magic about the aerodynamics...flies just like a cub.

As I gained more experience, and spent more time with my nose in the books (POH, FCTM, etc.), I discovered his over-simplistic advice coincided with the company SOP.

Amazing!!!!


PantLoad

[RYR-738-JOCKEY]

I see your point, but I beg to differ. A cub requires one pilot, a 737 requires two. That says something about the difference between them. I rest my case.

[Syawriahsitirb]

I have been flying the 737 for some time now and you can go on and on about crosswind takeoff techniques, but like 'PantLoad' mentioned, it's just an aeroplane. The techniques written in the manual are really for those just starting on the aircraft, but as you get more experience, it's a case of feel and react. Apply enough rudder to keep straight on the runway and a bit of aileron to keeps wings level as you rotate. You will prob find you need a little more of each as you lift off the ground, just keep everything straight and level and then about 200ft-400ft slowly start to release the rudder and aileron together. Simple as that. I don't know anything about units of aileron, as I'm not intelligent enough for that. I just fly the aicraft.

Just a quickie - I am little concerned about your comment Rainboe in regards to your frustration at co-pilots slowing to 250kts below 10,000ft. I have flown with guys who just love to kiss the barbers pole in the descent and I have indeed flown like this myself, but have you actually looked at what it saves you. In the time you spend flying around below 10,000ft, whether you're at 250kts or 320kts, it really makes no difference. Your comment of, "to hell with the birds, we're late," suggests you're putting pressure on the first officer to fly faster than perhaps he/she is comfortable with. This is completely and utterly wrong. It makes almost no different in time at all. Have a look at the FMC ETA when you change the descent speeds. If you delete the 250kts below 10,000ft constraint, on more or less every occasion, the ETA will not change. So rather than pressuring your FO's into doing things they're not comfortable with, just sit back in the knowledge that as they gain more experience, perhaps they might just start flying that little bit faster. Plus, is it not a rule now that we must fly 250kts below 10,000ft in the London TMA?

P.S. Are you one of those drivers who drives up the ar** of other drivers?

[misd-agin]

Wish that I had saved the email from a Boeing test pilot that had answered this exact question.

He said Boeing's policy was to use as much aileron as necessary to keep the wing level during the takeoff roll.

Aileron input prior to takeoff roll or during inital takeoff roll? Hmmm, how much aileron input due you need to keep the wings level? None.

[RYR-738-JOCKEY]

misd-agin: Try no aileron in max crosswind.
Not very pleasant. My first lesson in a C-172 taught me the opposite. In addition it contradicts everybody else in here.

And britishairwayS:
I'm talking about X-WIND T/O here. F.ex. rwy 18, W/V 225/33G46. Using "abit of aileron" will flip you over in no time. You need probably 10 units/45 degrees/half deflection on the yoke to have control. During rotation, that is.

[BOAC]

Ho hum - obviously no-one has looked at the links to previous threads and this keeps on coming up over and over again.

This from the Boeing 737 Training Manual, but good for all:

Maintain wings level throughout the takeoff roll by applying control wheel displacement into the wind. During rotation continue to apply control wheel in the displaced position to keep the wings level during liftoff. The airplane is in a sideslip with crossed controls at this point. A slow, smooth recovery from this sideslip is accomplished after liftoff by slowly neutralizing the control wheel and rudder pedals.

It's simple; it works - do not get drawn into making it more complicated! Think of it as:-

1) Keep the wings level ( a good idea)
2) Gently remove the rudder pressure (it gets tiring )

Maintain wings level throughout the takeoff roll by applying control wheel displacement into the wind. - that means 'as required', not needed at the start of the roll unless you are in a Tiger Moth

A slow, smooth recovery from this sideslip is accomplished after liftoff by slowly neutralizing the control wheel and rudder pedals. - this, of course, omits 'remove aileron input in a co-ordinated manner as you remove the rudder input' - well, that's how you fly, isn't it?

I shudder when I see 10 units go on before brakes off and stay there, unchanged

[Rainboe]

Aileron input prior to takeoff roll or during inital takeoff roll? Hmmm, how much aileron input due you need to keep the wings level? None.

The aim is to set and forget. You cannot 'fly' the aileron on in the early roll, so just set and leave and concentrate on holding the centreline. You will need it more>100kts when it will be set already, not giving you a rising wing to suddenly remember to counter.

I don't like home made, self imposed speed restrictions.....reason? .... 'for birds'. 'The birds' should not be in a control area. There is no such official speed restriction on the aeroplane. One hesitates to do it at London, but most of flying occurs elsewhere where skies are not so congested, and I do hustle for it.

This one is a regular Pprune item. Search should bring up several discussions on this topic, with all the old chestnuts regurgitated and spewed out!

[Rateofdescent]

1/ Crosswinds T/O are NOT the same in a CUB and a 737. On a CUB you should decrease input during T/O roll on the B737 you have to increase control input during the roll.
The only correct answer is in the FCTM, only the part 'as needed' is something you learn with experience. (indeed on a B737, speed=0, control wheel and rudder input needed=0)
Set and forget? Tell me how do you know the exact amount to be set before you started the T/O roll.
2/ 250Kts below 10.000. Check airspace class qualifications (by the way,the non-busy clear skies are often lower than class C). And yes, the reason is NOT birds.
(Anyway, most birds are now informed not to fly in controlled airspace without clc and Tx)
The ETA does change one or two minutes, that is if you also delete all other speed restrictions on the arrival, which occur sometimes above 10.000feet.

[Rainboe]

Set and forget? Tell me how do you know the exact amount to be set before you started the T/O roll.

What worked for me 18 years on the 747 also works on the 737. On top of the control wheel are marked divisions in units, what you use to check control wheel central. At the start of the roll, set 1 division into wind per 5kts crosswind component, and leave it there. Later on at high speed, you don't even have to remember which way to put it on, or cope with a wing lifting. It will hold the wing down until you get airborne. Do not take aileron off after lift-off, just leave it. The aeroplane will weathercock into wind, and then you will know when to relax it- once all yaw has washed out. You will find you gently start rolling aileron central, with no wing drop at all. The masters in the BA training section drummed it in long ago on the 747, and it works so well there is no other way.

I see it again and again. As pilots get airborne, off comes the aileron immediately, horrible wing drop followed by reapplication of double the amount of aileron (with a gasp). When the wheels lift off, the aeroplane is in instantaneous yaw, and all they can think is 'I'm airborne- I can't need this aileron!'. They do. All I can say is try it- you will find it works a treat.