Fly a Boeing? Why is right rudder trim needed in cruise?
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I know you're all talking Boeing, but the Airbus FCOM says to expect rudder trim to reside between 2.3 units Left and 1.0 units Right in the cruise. I rarely see it, if ever, sitting to the right. It's nearly always left trim.
I mention it because the cargo doors are on the right side of the A320 too so you wouldn't expect left rudder trim if this theory was true.
I mention it because the cargo doors are on the right side of the A320 too so you wouldn't expect left rudder trim if this theory was true.
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Care to expand on your question? I'm not sure I follow your logic
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Coriolis, old chap. I use to notice the amount of trim reducing as I neared Banjul in the old days.
Last edited by Straight & Level; 2nd Apr 2013 at 14:33. Reason: Typo. Again.
Jim smitty.
The 737 crabbing is because the landing gear design includes a shimmy damper that permits the mlg to castor left or right.
The 737 crabbing is because the landing gear design includes a shimmy damper that permits the mlg to castor left or right.
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Since nobody knows if this is even real and probably isn't, A
OA changes some at cruise so the slight power reduction at cruise or AOA change is the only thing different. P factor on a prop airplane required right rudder in a climb and not in cruise. If the engine rotates the counterclockwise direction I guess the opposite would be true but since it goes out the same exhaust the only effect would be the intake pulling air further out on one engine vs the other.
OA changes some at cruise so the slight power reduction at cruise or AOA change is the only thing different. P factor on a prop airplane required right rudder in a climb and not in cruise. If the engine rotates the counterclockwise direction I guess the opposite would be true but since it goes out the same exhaust the only effect would be the intake pulling air further out on one engine vs the other.
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CRABBED TAXYING 737s.
The reason for the B737 appearing to taxy with drift is because the MLG torque links have a damped mechanism to allow limited castoring of the mainwheels.
If you are lucky enough to get close to one, check the "knee-joint" at the front of the MLG and you'll see the shiny portion of the damper, a bit like an oleo.
I try to reassure my F/Os when they're getting twitched about X-wind landings, that the airframe owns the first 15 knots of crosswind, as per autolands, and they've just got to sort the other 18/20 depending on winglets!
So far it seems to reassure them and me................
If you are lucky enough to get close to one, check the "knee-joint" at the front of the MLG and you'll see the shiny portion of the damper, a bit like an oleo.
I try to reassure my F/Os when they're getting twitched about X-wind landings, that the airframe owns the first 15 knots of crosswind, as per autolands, and they've just got to sort the other 18/20 depending on winglets!
So far it seems to reassure them and me................
Last edited by BARKINGMAD; 2nd Apr 2013 at 23:13.
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None of us believe that because once established in flight we all know no rudder is required no matter what the wind is doing. Coriolis effect only affects how the atmosphere circulates in the northern and southern hemisphere, not how you have to fly your airplane. Maybe you are just kidding but if you aren't get a book out and read how it works.
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None of us believe that because once established in flight we all know no rudder is required no matter what the wind is doing. Coriolis effect only affects how the atmosphere circulates in the northern and southern hemisphere, not how you have to fly your airplane. Maybe you are just kidding but if you aren't get a book out and read how it works.
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So, this thread is taking an interesting 'turn'. Pun intended 
I still maintain that the likely culprit is uneven cooling in the rudder actuator mechanism, as do Boeing it seems (thanks SMOC and main_dog). Now granted, it's been a while since I studied my ATPL theory subjects but I'm struggling to understand how Coriolis affects the rudder trim required in steady-state cruise.
I still maintain that the likely culprit is uneven cooling in the rudder actuator mechanism, as do Boeing it seems (thanks SMOC and main_dog). Now granted, it's been a while since I studied my ATPL theory subjects but I'm struggling to understand how Coriolis affects the rudder trim required in steady-state cruise.
once established in flight we all know no rudder is required no matter what the wind is doing.
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He's actually wrong about coriolis and P factor on a turbo prop.
Anyway, there is a simple reason for this rudder trim phenomenon and that is because the right hand engine is started first the right hand thrust pixies are that little bit more warmed up than lefties and, therefore, produce that little bit more thrust, hence yaw, hence trim required. Easy.
Anyway, there is a simple reason for this rudder trim phenomenon and that is because the right hand engine is started first the right hand thrust pixies are that little bit more warmed up than lefties and, therefore, produce that little bit more thrust, hence yaw, hence trim required. Easy.
Ah yes, the pixies!
I don't know the answer to the coriolis question, but if a mass of air moving within the atmosphere above the planet is affected by the coriolis force and veers slightly, then why not an aircraft also moving in the atmosphere above the planet?
Indeed - I have just checked my dictionary, and its' definition of coriolis is; "A hypothetical force used to explain the deflection in the path of a body moving relative to the earth"
(If aircraft are affected by this, I would not have thought that rudder trim is the answer - the aircraft will account for it by comparing its required track with its actual track and adjust heading accordingly. Rudder trim is used to adjust for any slight variations in the airframe - one wing fractionally more draggy than the other - asymmetric fuselage drag etc.)
I don't know the answer to the coriolis question, but if a mass of air moving within the atmosphere above the planet is affected by the coriolis force and veers slightly, then why not an aircraft also moving in the atmosphere above the planet?
Indeed - I have just checked my dictionary, and its' definition of coriolis is; "A hypothetical force used to explain the deflection in the path of a body moving relative to the earth"
(If aircraft are affected by this, I would not have thought that rudder trim is the answer - the aircraft will account for it by comparing its required track with its actual track and adjust heading accordingly. Rudder trim is used to adjust for any slight variations in the airframe - one wing fractionally more draggy than the other - asymmetric fuselage drag etc.)
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P factor was taught when I was learning and the same laws apply now. Trim once in an ocean of air doesn't compensate for wind, only for misrigging or assymetrical thrust. A jet engine, if it has any AOA, would have slightly more intake on the downward spinning fan but I have never noticed enough to care. I think a lot of folks here are pulling our leg to see if we will bite. Then we have a few that....never mind.
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Boeing Flight Operations Review 737-22
An airplane in steady cruising flight may require some degree of
lateral and/or directional trim inputs to minimize drag. The
trim requirement can arise from improper rigging of flight
controls after maintenance, internal load distribution, fuel
unbalance, and engine thrust setting imbalance. The degree of
trim inputs required will depend on two basic factors: 1) The
degree of controls misrig, lateral unbalance, etc., and 2) Trim
technique employed
lateral and/or directional trim inputs to minimize drag. The
trim requirement can arise from improper rigging of flight
controls after maintenance, internal load distribution, fuel
unbalance, and engine thrust setting imbalance. The degree of
trim inputs required will depend on two basic factors: 1) The
degree of controls misrig, lateral unbalance, etc., and 2) Trim
technique employed