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chris41

Rudder Trim

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Had a landing today (PMDG 737-900) with a 15 knots of crosswind. How do you determine how to set the rudder trim? Shooting the ILS approach I could see where I needed to point the nose and just before touchdown I used quite a bit of rudder to line up center line and had a good landing but I assume that you could also just set the rudder trim instead of crabbing on down to touchdownIThanks,Chris Porter

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Had a landing today with a 15 knots of crosswind. How do you determine how to set the rudder trim? Shooting the ILS approach I could see where I needed to point the nose and just before touchdown I used quite a bit of rudder to line up center line and had a good landing but I assume that you could also just set the rudder trim instead of crabbing on down to touchdownThanks,Chris Porter
Actually you don't use rudder trim for landing in a cross wind. It sounds like you did the appropriate technique by correcting the crab with rudder just before touch down.

George Morris

 

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Actually you don't use rudder trim for landing in a cross wind. It sounds like you did the appropriate technique by correcting the crab with rudder just before touch down.
Ah, thanks.When do you use the rudder trim?Thanks, Chris Porter

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Ah, thanks.When do you use the rudder trim?Thanks, Chris Porter
I am not a 744 driver but I don't believe it's ever used in normal flight. Yaw dampners should take care of things. You should have symetrical thrust at all times. In an emergency engine failure the systems automatically assist in helping compensate for the asymetrical thrust. But you still have to use the rudder and trim to compensate.If your interested in seeing how good the autopilot and aerodynamic models are, fail an outboard engine and watch the auto pilot land in a significant cross wind. :( In the single engine aircraft I fly, I use rudder trim in a long climb and cruise.

George Morris

 

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Yaw Dampers don't assist in a engine-out asymmetric thrust scenario, but it depends on when the failure happened. If the failure happened during a multiple CMD approach under 1500' RA, the AFDS would correct for the asymmetric thrust, but only at that time (it's almost identical to the 767 layout). You need to adjust the rudder trim manually to compensate for the added yaw. Rudder trim is only used to compensate for asymmetric thrust, which the amount of trim required will change based on how much thrust the operating engines are giving. Trim is a secondary flight control though. Use the pedals first, then trim the pedals into the neutral position. The crosswind technique is actually rather simple. You crab into the winds with the ailerons (not the rudder) until the aircraft's tracked path matches the runway heading. You then use the rudder to align the nose of the aircraft with the runway under 500' RA.I also want to note that MSFS is buggiesh when it comes to a sophisticated yaw damping system. I don't think the yaw dampers work properly when the autorudder option in the realism menu isn't checked.


Kevin Hester,

 

Indianapolis, Indiana

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