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Guest tmanaon

Takeoff in cross wind conditions

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Guest tmanaon

I have noticed during numerous real world flight as a passengeer in 747-400's that during (what i would assume are) cross wind takeoffs, the trailing edge on the wings beyond the flaps are set slightly up or down and stay that way until wheels up and then they line up with the edge of the wing..i hope you guys know what i'm talking about..this is the far edge of the wings that does not bend when the flaps are activated.When i am taking off with the PMDG 747-400 in crosswind conditions, i have to keep adjusting the nose wheels with my pedal so as not to drift off the runway during my takeoff roll. I am not sure that this is the proper way to do this. Is there a way to use the leading edge as indicated above perhaps with the rudder preset to an angle to achieve the same purpose without constantly using my pedals and nose wheel?I hope this makes sense.Anthony

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Anthony,I guess you are talking about the ailerons (control surfaces for banking). If my memory serves me right there is a procedure to bank slightly into the wind during take-off. Maybe this is what you have seen? I also think this technique is discussed in the 744 Type Rating Course: Lesson 2 . Well worth looking into!Hope it helps,


Mats Johansson
PMDG Flight Test Dept
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I am not 747 rated but have 30 yrs real flying...Cross wind procedure is normally based on using nose steering until rudder becomes effective. Ailerons are used in smaller aircraft for both taxi and takeoff to "unload" the upwind wing to prevent gusts from generating asymmetrical lift. I'm not surprised that it works as well in a Heavy. Pilots "turn into the wind" with the yoke and may decrease the deflection as the airspeed builds up, depending on "how it feels." Take off occurs with wings level, and the aircraft is flown on the runway heading until above 400 AGL, so at some point the aileron deflection needs to come out. It's not uncommon to allow some bank after liftoff if the pilot's goal is to keep the aircraft over the runway centerline... the bank will introduce a crab angle to accomplish this.


Dan Downs KCRP

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Guest neeraj.pendse

Based on my real world flying experience of 4 years, I am glad my understanding is exactly what Dan has said. I have noticed heavies using crosswind correction just like the light airplanes- except that probably heavies do not use full aileron deflection into the wind at the start of the takeoff roll like the light airplanes do.Also, I might add that the aileron deflection into the wind feels like it gives some help in directional control on takeoff roll as well ...- Neeraj.

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Guest tmanaon

At what point is the rudder used (if at all) during the takeoff roll under crosswind condition? I take it from your answer that the rudder is not preset at a defined angle prior to the start of the takeoff roll?Anthony

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We need a type-rated pilot to chime in... most aircraft rudder effectiveness starts at about 40 kts. There's a transition between nosewheel and rudder control where both are used. Rotation in a stiff crosswind requires a positive noseup action to effective pick the plane off the runway to prevent putting side loads on the gears. I expect it is actually easier in a turbojet than a piston twin, the C414 I fly rotates at 90 kts where the crosswind component is a larger fraction of the airspeed than at turbojet Vr speeds.


Dan Downs KCRP

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Guest capntom

In flying the 747-400 ( I fly the 400UF) a fair bit of wheel is cranked into the wind due to the fact that the significant sweep of the 747 wings makes it easy for the crosswind to cause wing lift and roll on takeoff. However the idea is generally not to apply so much wheel deflection so as to cause spoiler deflection, which causes drag and loss of lift, undesireable on takeoff. As the aircraft has a large verticle stabilizer, there is significant weathervaning tendency, opposite rudder is necessary. At slow speeds the rudder application will also cause nosewheel movement which will help some, though the nosewheel on the 747 is lightly loaded and will skid easily were one to generate a significant angle such as with the tiller.Tom

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>I have noticed during numerous real world flight as a>passengeer in 747-400's that during (what i would assume are)>cross wind takeoffs, the trailing edge on the wings beyond the>flaps are set slightly up or down and stay that way until>wheels up and then they line up with the edge of the wing..i>hope you guys know what i'm talking about..this is the far>edge of the wings that does not bend when the flaps are>activated.>>When i am taking off with the PMDG 747-400 in crosswind>conditions, i have to keep adjusting the nose wheels with my>pedal so as not to drift off the runway during my takeoff>roll. I am not sure that this is the proper way to do this. >Is there a way to use the leading edge as indicated above>perhaps with the rudder preset to an angle to achieve the same>purpose without constantly using my pedals and nose wheel?>>I hope this makes sense.>>AnthonyI've used the crosswind conditions in flight simulator but it's very exagerated so I don't use it. So you may have to apply a little rudder pressure as you're going down the runway. When the airplane is airborn, the procedure is to bank into the wind slightly and apply a little opposite rudder to keep to airplane from turning. You will actually be crabing over the runway. Each aircraft has a maximum crosswind component that should not be exceeded. If that component is exeeded such as in high wind conditions, it's very difficult to keep the airplane from slipping sideways over the runway, especially when landing. I remember reading about it somewhere and I think it was in the PMDG 747 manual or the Real 747 947 page manual. Ken.

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Guest capntom

The Boeing limitations are a "Demonstrated value". 30 knots under dry conditions. Each carrier typically as company linits for various conditions such as wet, snow and ice etc.One factor to keep in mind here is the further directional control limitations that are imposed by a worst case engine failure on takeoff. Failure of the upwind outboard engine causes full rudder to be requitred, A hefty push! It is a big plane and even under normal X-wind conditions the foot pressure for rudder correction is significant.Tom

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