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The Snake
11th Dec 2006, 14:15
Please your opinion on the following aircraft (Regional Jet) handling question.

Would you use rudder during aircraft rotation in crosswind conditions to push the nose into the wind? This in purpose to assure a correct drift angle to maintain runway track after lift-off.

Or...., wait until after lift-off and then bank slightly into the wind to maintain runway track.

I've a discussion with a collegue regarding the correct handling...:}

Feedback highly appreciated,

The Snake

Rainboe
11th Dec 2006, 15:32
Because of the crosswind element, as the aeroplane lifts off, it becomes in a slight yaw situation as the relative direction of the wind is not aligned with the runway direction, which is what the aeroplane is pointing in. This yaw situation results in the aeroplane naturally turning slightly into wind by itself. Only a small gesture is needed to complete the heading change you want to allow enough drift to maintain track. A small turn on the ailerons is all that is needed. I don't think you should use rudder- you are causing another yaw situation, and when you remove the rudder input, you are creating a reverse yaw situation in the other direction. It is probable that you will not end up with the aeroplane settled on the heading you want after all that yawing in either direction, so IMO just use a little aileron to turn where you want it and keep the aeroplane balanced. Anytime you try and use rudder as a turn aid, you create a roll element and it just becomes untidy.

captainpaddy
11th Dec 2006, 19:08
If you are taking off in a crosswind, you will require a rudder defelction in the opposite direction to the wind direction (left crosswind requires right rudder) to maintain the runway centreline. There is therefore no need for an actual deflection of the rudder to yaw the aircraft into wind. On realeasing the rudder from the position you had it in to maintain the centreline, the aircraft will naturally yaw into wind itself.

I personally release the rudder to neutral as the aircraft gets airborne. This almost always results in the aircraft assuming the appropriate heading to maintain the runway track all by itself. However, once the rudder is centered you should use aileron only (assuming your aircraft has a yaw damper) to correct the aircraft track if need be, exactly as you would for any other turn.

Intruder
11th Dec 2006, 19:33
I don't know specifically about RJs, but in general the same control inputs (aileron & rudder) you need to maintain track just before rotation are a good start for rotation and liftoff. After you're airborne, level the wings and let go any rudder input to start your initial outbound track. The initial aileron and rudder inputs will likely set you up on a reasonable track with some crosswind correction. Fine tune it after the wheels are coming up.

BOAC
11th Dec 2006, 20:28
Snake - Cpt Paddy and Intruder have the correct answer. It is so simple. 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:) )

Rainboe
11th Dec 2006, 22:13
But that hasn't answered the question! So where am I incorrect in my answer that I am excluded from your official stamp of approval (not that it's needed anyway!)?

BOAC
11th Dec 2006, 22:53
As I said, posts 3 and 4 answered it, did they not?

Blip
11th Dec 2006, 23:05
Please your opinion on the following aircraft (Regional Jet) handling question.

Would you use rudder during aircraft rotation in crosswind conditions to push the nose into the wind?

Perhaps the question cannot be answered because it includes incorrect assertions in the first place.

Yes you would use rudder deflection during rotation in crosswind conditions, but it would not be to push the nose into the wind but rather to keep the nose parallel to the runway during rotation. Once airbourne, you gently reduce your leg pressure on the rudder pedals. The pedals subsequently move back to the centre and the aircraft naturally "weather vanes" into the direction of the wind and subsequently continues to track the runway centreline. Meanwhile use the ailerons to keep the wings level. As the amount of rudder input reduces, so too does the aileron input.

Intruder
13th Dec 2006, 01:19
but rather to keep the nose parallel to the runway during rotation.
Not quite...

Rudder (and nosewheel steering, when available prior to nosewheel liftoff) is used to maintain track down the runway centerline. Depending on the airplane and the crosswind component, the airplane may not be aligned with the runway while tracking the centerline.

After the airplane is airborne, rudder pressure is unneeded on most airliners, because the roll spoilers and yaw dampers provide yaw control in turns. So, once the wings are leveled after liftoff, rudder input should no longer be needed. Use aileron input to adjust heading/track outbound.

nugpot
13th Dec 2006, 06:27
After the airplane is airborne, rudder pressure is unneeded on most airliners, because the roll spoilers and yaw dampers provide yaw control in turns. So, once the wings are leveled after liftoff, rudder input should no longer be needed. Use aileron input to adjust heading/track outbound.

On the CRJ you can feel unbalanced flight immediately. You also need rudder during low speed turns to keep the a/c balanced - if balanced flight is important to you obviously. It seems more and more of the newer pilots don't care.

I think you are making this too technical. After lift-off, maintain balanced flight (first) and runway track (second) using whatever control inputs are necessary.

The Snake
14th Dec 2006, 14:37
Thanks to all for the reply's.

Good point Blip noted. It's indeed a false assumption to use the word 'push the rudder', while reducing (smootly) pressure on the pedals close to Vr and thereafter to maintain track is what you actually do.

Sometimes I lost a bit the picture of rudder use during crosswind take-offs :rolleyes: . But everything is much more clear now.

Luckily the past few days were windy in the UK and Ireland, so I could practice your advises in real life...:)

Happy take-offs!

The Snake

MaxReheat
14th Dec 2006, 17:04
"if balanced flight is important to you obviously. It seems more and more of the newer pilots don't care."

And a lot of older ones, too. A few years back a co-pilot said to me that I must have done some gliding. Why do you say that, I asked. Because you're the only captain (moderate size company) I've come across who keeps the ' ball in the middle'.

And while I'm at it, centre-line tracking post take-off is also becoming something to be filed under 'can't be bothered about'. I frequently line up, stiff crosswind, and watch the aircraft departing ahead drift further and further from the extended centreline - no apparent effort whatsoever to maintain it. What are they teaching at flight schools nowadays?:{

CNTDSCT
14th Dec 2006, 17:05
Im lost....are we in the training forum or in a QUALIFIED AIRLINE PILOT one?
If one doesnt know the basics of a crosswind take/off (and not talking about perfect crosswind t/os), what is this person doing flying passengers around??
:ugh: :eek:

Best Regards to all who take their time to actually explain such method...

Anotherflapoperator
14th Dec 2006, 18:34
I've also found a lot of older high hour Jet pilots, well the ones I fly with who are ex 707 and the like NEVER touch the rudder except in the last instant of a crosswind landing. They will also always trim out using the rudder trim and never the aileron trim as well.

Our old 146-100 is exceptionally bent, I suspect the flaps are a degree or so out as it flies straight as a die with the ailerons offset by about 2-3"! Some roll moment going on there. Very few other pilots at my base will ever adjust the aileron trimmer, and I find a full turn will balance it right at cruise speed. We need a quarter turn of rudder trim but this is power related whereas the aileron trim is speed related.

Two of them, like me, apply rudder on crosswind takeoffs, keeping it applied as they rotate and gently feeding it off to allow the a/c to centre.

I suppose as we have the short one, it does lack much stability, and can't be dispatched without the yaw dampers working as well.

Now I'm no test pilot, but most of the experienced guys keep their feet up and out of the way most of the time. What do I know anyway? Perhaps my fiddling is totally unneccessary.

Q400 Pilot
14th Dec 2006, 18:56
A quick point regarding Blip's post (sorry if I have misunderstood you). An aircraft only "weather vanes" when on the ground. As soon as it is airbourne the aircraft no longer has a tendancy to turn into wind.

Chesty Morgan
14th Dec 2006, 19:06
Yes it does! It's called drift.

Q400 Pilot
14th Dec 2006, 19:15
Not the same thing at all. An aircraft will maintain heading wherever the wind is coming from when airbourne (assuming it is trimmed). An aircraft drifts downwind, it doesn't turn into it.

Chesty Morgan
14th Dec 2006, 19:22
It will maintain a heading if that's what you or the autopilot are trying to fly, but the track will change. If however, you are trying to maintain a track, such as the runway centreline, then it wont. Try landing the Q400 without a yaw damper in a gusting cross wind. With low speed the slipstream effect is reduced and the old girl swings around. Yes it was trimmed.

Q400 Pilot
14th Dec 2006, 19:38
Fair enough, if you speak from experience. Maybe we can discuss it further when we next fly together.;)

one dot right
14th Dec 2006, 21:05
What did Rainboe say that was so incorrect? Seemed like a perfectly reasonable course of action.

Rainboe
14th Dec 2006, 22:12
I'm still trying to work out why my answer was not 'approved'!

one dot right
14th Dec 2006, 22:39
Upset someone Rainboe?

Blip
14th Dec 2006, 23:58
What did Rainboe say that was so incorrect? Seemed like a perfectly reasonable course of action.

Rainboe said:

Because of the crosswind element, as the aeroplane lifts off, it becomes in a slight yaw situation as the relative direction of the wind is not aligned with the runway direction, which is what the aeroplane is pointing in.

How did Rainboe manage to track the runway centreline up to the point of rotation? Why is the aeroplane pointing in the direction of the runway and not the direction of the relative wind? Was it not with rudder opposing the:
aeroplane naturally turning slightly into wind by itself?

If you have a crosswind from the right, you will have left rudder opposing the "aeroplane turning into wind by itself". You have right aileron to counter the right wing producing more lift than the left wing. You maintain this cross control during the rotation. You do not just suddenly abandon the rudder!

Once airbourne you still have these crossed controls. The aircraft will still be heading in the direction of the runway centreline, while sideslipping to the right (into wind). This sideslip will equal the crosswind and the two cancel out. The aircraft is therefore tracking the runway centreline.

Now at this point all you need to do now is slowly relieve the pressure on the rudder pedals until they have naturally come back to the centre. When you say:

I don't think you should use rudder- you are causing another yaw situation, and when you remove the rudder input, you are creating a reverse yaw situation in the other direction.

it seems to me you might be unclear as to where the rudders are at this point in time. I might be wrong but it seems you are visualising the pilot [b[initiating[/b] rudder input at this time to cause the heading to change. This is not the case. At this point in time the rudder input is already there and is in fact now being reduced back to centre.

While the rudder displacement is reduced, the ailerons are reduced too. While this happens, the aircraft has a natural tendency to turn ever so slightly and assume the correct heading to continue tracking the runway centreline. You initiate the movement of the rudder first and then the ailerons in response to the reduction in induced roll. In other words you consciously move the rudder in a deliberate and controlled manner, and move the ailerons with whatever response is required to keep the wings level.

At this point in time, the wings are now level, all the controls are centred, and the correct heading is established which causes the aircraft to continue to track the runway centreline.

I hope what I have written is clear. Being able to demonstrate it in the real world would be so much easier!

Intruder
15th Dec 2006, 02:30
Another way of looking at the situation is that it is exactly the same as a crosswind approach/landing situation, in that there are 2 ways to fly the approach: Wing down/top rudder (slip) or crab.

Both have the same net effect, in that they allow the airplane to track the localizer or extended runway centerline. Both require some kind of transition from the airborne to the runway environment. Both allow some combination of the basic 2 techniques. Both become "intuitive" to the experienced pilot, who may not overtly realize which [combination of] technique he employs, and in what sequence.

The one difference is that in the takeoff case, a slip is not normally seen as a "proper" technique once airborne, so a transition to balanced flight is "always" required. The choice is then to maintain runway heading or to "crab" into the wind to maintain the extended runway centerline track. Both are "proper" techniques, and one or the other may be required in specific departure procedures (though it appears that maintaining track is becoming the more frequent requirement).

IMO, the bottom line is that a controlled transition from runway to airborne environment must be made, and specific techniques for doing so depend on the airplane and installed equipment.

Rainboe
15th Dec 2006, 05:49
Once airbourne you still have these crossed controls. The aircraft will still be heading in the direction of the runway centreline, while sideslipping to the right (into wind). This sideslip will equal the crosswind and the two cancel out. The aircraft is therefore tracking the runway centreline.

Now at this point all you need to do now is slowly relieve the pressure on the rudder pedals until they have naturally come back to the centre. When you say:


Blip, once airborne, almost immediately you have to reduce rudder input to zero. I have found that the aeroplane will not weathercock enough into wind to counter the drift by itself. You see this when watching planes sliding downwind after take-off when they haven't applied enough drift- very few ever move upwind. So my answer to Snakes initial query in the first post:
Would you use rudder during aircraft rotation in crosswind conditions to push the nose into the wind? This in purpose to assure a correct drift angle to maintain runway track after lift-off.

Or...., wait until after lift-off and then bank slightly into the wind to maintain runway track.
....was not to then use rudder into wind to apply further drift required but to bank slightly towards the crosswind keeping balanced flight until you have the full heading offset required to maintain runway track.

Blip
15th Dec 2006, 08:59
Ok Rainbow. I think we are on the same page more or less.

The technique I describe works very well for me. The whole process of rotation and initial climb always feels under control and therefore I have no inclination to rushing the rotation and risking a tailscrape.

Also you might be right about there being some crosswind not being accounted for by the crossed controls once airbourne, however the aircraft type I fly has a map referenced to track and it does not ever :hmm: indicate any drift more than a degree or so.

Also to clarify, I begin to reduce rudder input as soon as I am finished with the rotation and am at the correct attitude for initial climb (15 - 18 degrees nose up). This would be at about 100 ft AGL. The time it takes me to then centre the rudder pedals is about 3 - 5 seconds depending on how much they're displaced. So even if I was drifting a degree or so, it would only be for a matter of seconds.

Of course as you climb, the wind tends to strengthen and change direction as well. Once the rudder is back to centre I would certainly be using aileron to adjust the heading in an attempt to maintain runway track.

:)