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FLEX1978

Sim rudder technique

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As we all know touching the rudder in any regime of flight except for engine out or decrab is considered very bad practice in transport category aircraft.I find crosswinds in FS highly unrealsitic regading this, I am able to get the aircraft down smoothly but the approach in high crosswinds and gusts (within aircraft limits) seem to require some rudder input before the decrab.Is this just a FS limitation, Can anyone give me some tips? If I was to use the rudder in a real Sim session on approach I would be failed.Thanks


Rob Prest

 

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How do you crab an aircraft sideways without touching the rudder? From what I saw (and heard mind you) is that to keep on a straight flight path in crosswinds, you have to impart yaw to keep the flight path of the aircraft lined up with the runway and to do so, you have to use rudder inputs. At least it was this way when I was a crew cheif on helos many years ago. Would not the same be true of fixed wing aircraft?


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How do you crab an aircraft sideways without touching the rudder? From what I saw (and heard mind you) is that to keep on a straight flight path in crosswinds, you have to impart yaw to keep the flight path of the aircraft lined up with the runway and to do so, you have to use rudder inputs. At least it was this way when I was a crew cheif on helos many years ago. Would not the same be true of fixed wing aircraft?
What your describing sounds like a forward slip, fine for a Cessna but not a large aircraft.I don't like using wiki but here's a example. I don't know of any airlines that allow the sideslip to be used.http://en.wikipedia.org/wiki/Crosswind_landing

Rob Prest

 

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B-52's have a knob on the center counsel that sets the main gear angle, allowing a touchdown in a crab. The reason is because of the wingspan they are unable to drop a wing into the wind, which is the key to "de-crabbing" on landing. Nothing is real on a computer, but you can still mimick the cross wind technique in MSFS fairly well. Don't think of the rudder as the primary control rather combine bank and yaw in one simultaneouse application of bank into wind and yaw to center line. Then watch: If you drift downwind increase bank and if you drift upwind decrease bank while in either case keeping lined up on centerline with your yaw. Constant minor smooth adjustments, but it shouldn't take long... never float, be on the money speed wise. The cross control condition will decrease the amount of flare needed, but don't land on nose wheel. First touch should be upwind main, then downwind main the last the nose.Flying out of CRP has made this second nature for me.


Dan Downs KCRP

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B-52's have a knob on the center counsel that sets the main gear angle, allowing a touchdown in a crab.
Hahahaha now THAT is great engineering! :( Why did they never build that feature into a civil aircraft? :( Had no idea the B-52 could do this, it makes perfect sense of course. What's the max. crosswind the aircraft is certified for?Cheers,Markus

Markus Burkhard

 

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I have a photo of the cockpit of the B-52D in the USAF museum, the placard below the knob has a setting for 20kts at 50 deg. I've not read the actual limitation specification.


Dan Downs KCRP

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A friend of mine, highly experienced comercial pilot and former fightfighter told me that you never use the rudder to crab-decrab in crosswinds landings. He said it's all done with ailerons. He currently flies MD-8x and A320-321, but he's flown pretty much any kind of airliners, from 737s to long hawlers

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A friend of mine, highly experienced comercial pilot and former fightfighter told me that you never use the rudder to crab-decrab in crosswinds landings. He said it's all done with ailerons. He currently flies MD-8x and A320-321, but he's flown pretty much any kind of airliners, from 737s to long hawlers
You should never use the rudder to crab, but you have to use it to de-crab. Maybe you misunderstood him

Rob Prest

 

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I can see the rudder deflection on jets landing in CRP (regionals and 737s)


Dan Downs KCRP

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That's most likely the case, yes. It was like a third grade and I can hardly remember everything he told me.

... Maybe you misunderstood him

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You should never use the rudder to crab, but you have to use it to de-crab. Maybe you misunderstood him
Right. I don't fly large aircraft but here is my understanding : you set the plane on the right trajectory (ie in a crabbed attitude) using whatever controls are necessary (ie ailerons and rudder - but probably a very small amount of the latter). Then you maintain it that way until it is time to decrab - and that is when you use the rudder. But the wings remain horizontal all the way to touchdown (due to limited ground clearance - especially with engines slung under the wings - but I guess passengers comfort may also be a factor). On the other hand, in a light plane or a 3-axis ultralight, you can also crab/decrab but the prefered approach is often the one described by Dan (low wing into the wind with crossed controls; touchdown first with the upwind main gear...)Bruno edit : PS : didn't know either about the sideslip method described in the link to Wiki above. It would be interesting if a rw airline pilot could comment about its use.

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According to that Wiki article, both sideslip and crab use the rudder to pull off the manuever.

CrabThe airplane can land using crab only (zero side slip) up to the landing crosswind guideline speeds.On dry runways, upon touchdown the airplane tracks towards the upwind edge of the runway while de-crabbing to align with the runway. Immediate upwind aileron is needed to ensure the wings remain level while rudder is needed to track center line. The greater the amount of crab at touchdown, the larger the lateral deviation from the point of touchdown. For this reason, touchdown in a crab only condition is not recommended when landing on a dry runway.On very slippery runways, landing the airplane using crab only reduces drift towards the downwind side of a touchdown, and may reduce pilot workload since the airplane does not have to be de-crabbed before touchdown. However, proper rudder and upwind aileron must be applied after touchdown to ensure directional control is maintained.SideslipThis sideslip crosswind technique is to maintain the aircraft's heading aligned with the runway centerline. The initial phase of the approach is flown using the Crab technique to correct for drift. The aircraft heading is adjusted using rudder and ailerons to align with the runway. This places the aircraft at a constant sideslip angle, which its natural stability will tend to correct. Sufficient rudder and aileron must be applied continuously to maintain the sideslip at this value. The dihedral action of the wings has a tendency to cause the aircraft to roll, so aileron must be applied to check the bank angle.
With a slight residual bank angle, a touchdown is typically accomplished with the upwind main wheels touching down just before the downwind wheels. Excessive control must be avoided because over-banking could cause the engine nacelle or outboard wing flap to contact the runway/ground.In strong crosswind conditions, it is sometimes necessary to combine the crab technique with the sideslip technique.And yes, I knew that B-52s can land and track down the runway sideways, I grew up on Air Force bases and 2 of which were SAC bomber bases which had B-52s.

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Darrio,

A friend of mine, highly experienced comercial pilot and former fightfighter told me that you never use the rudder to crab-decrab in crosswinds landings. He said it's all done with ailerons. He currently flies MD-8x and A320-321, but he's flown pretty much any kind of airliners, from 737s to long hawlers
I don't want to get into an argument about cross wind landings. What your "friend" said is mostly true. Most if not all large commercial jets can land in a full crab at the aircraft/air carrier limit (varies by carrier but normally about 25 knots). The gear is very strong. There is a better and smoother way. The aircraft will be flown in a crab until shortly before touchdown. "Push off" the drift angle just before touchdown "don't kick it off". Feed in the rudder smoothly and match it with the required amount of aileron control. A bigger worry in strong crosswinds is the effect on the spoilers and the effect the crosswind will have on the thrust reversersBill

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Hi,Speaking from the point of view of operating the B738W in the real world, FS has very limited capabilities when it comes to crosswinds, in the real world the approach regime is a lot more dynamic with winds shifting and in a lot of cases in the stronger crosswind conditions you experience a certain degree of windshear. FS is unable to replicate the dynamic environment that we face in day to day operations. The B738 can be really unforgiving and can be quite twichy and very sensitive, especially the aileron channel, to fly in the landing configuration,more so in the F40 configuration!The are several techniques, again i'm referring to the techniques used as per my airlines operating manual, the autopilot on the aircraft can land with a maximum crosswind component of 15 knots, however during the flare the aircraft does not decrab it lands with the crab in which can be a little uncomfortable as the aircraft lurches after touchdown. In wet runway conditions we are encouraged to land land with the crab in. In gusty, wet/slippery runway, strong crosswind conditions, great care is advised as not only is it advisable to land with the crab, one has to be very careful when selecting reverse thrust the aircraft may well start to slide,in this instant we select idle reverse and touch the toe pedals to disconnect the autobrake and brake manually. When the aircraft is is back on the centreline you can once again cautiously use reverse thrust beyond the idle selection.In the crosswinds, in dry conditions we tend to use the decrab method doing so in the later stages of the approach (during the flare) remembering to apply opposite aileron to prevent the wing drop. It is difficult to give a precise time when to gently apply rudder to straighten her out but you use your judgement, most of the time you get it right and sometimes not so! I'm sure every pilotyou ask will tell you no 2 landings are ever the same:-)We dont tend to use wing down method as this greatly increases the risk of stiking the engine pod or even the aircraft so in the B738 it is not recommended.Crosswinds can be quite tricky even more so when you aircraft has huge winglets!Hope this helps,James

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Thank You very much :)


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