Aircraft Trimming -A320
Thread Starter
Join Date: Aug 2001
Location: Above the Horizon
Posts: 124
Likes: 0
Received 0 Likes
on
0 Posts
Aircraft Trimming -A320
The A320 FCOM states that in normal cruise around M.77 in straight flight with the AP engaged and fuel in the wing tanks distributed symmetrically the rudder trim should stay between 1 degree right and 2.3 degree left.
Why is it different for left and right?
Why is it different for left and right?
Join Date: Jul 2009
Location: London
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Anyone have any ideas?
It reads strangely from the translation into English.
I understand the rudder varies 1.5 degrees left and right but the indication is different between the left and right. Not sure why the indication is different?
It reads strangely from the translation into English.
I understand the rudder varies 1.5 degrees left and right but the indication is different between the left and right. Not sure why the indication is different?
Join Date: Jun 2014
Location: Village of Santo Poco
Posts: 869
Likes: 0
Received 0 Likes
on
0 Posts
Join Date: Jul 2009
Location: London
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
The FCOM basically says that the actual trim is from 1.5 left to 1.5 right but says the indication is different between left and right. At least that is how I read the translation. Have a read in the FCOM and see what you think.
I have no idea why the indication would be different.
I have no idea why the indication would be different.
Quote from Lantirn:
"May be due to the fact that engines turn clockwise as seen from the cockpit..."
Errr... that would be true if the cockpit was behind the engines!
Both CFM and IAE engines are right-hand tractors, so rotation is anticlockwise as seen from in front (i.e., looking aft).
"May be due to the fact that engines turn clockwise as seen from the cockpit..."
Errr... that would be true if the cockpit was behind the engines!
Both CFM and IAE engines are right-hand tractors, so rotation is anticlockwise as seen from in front (i.e., looking aft).
Join Date: May 2007
Location: FL390
Age: 38
Posts: 224
Likes: 0
Received 0 Likes
on
0 Posts
Yep you are right, I wanted to say when looking in the direction of travel! The correct term is anti clockwise sure.
Regarding the FCOM and the trim, what it says there is that the aircraft when flying should have (theoretically) zero rudder trim input. With this in mind, when it is trimmed, it should be at zero. Because the average value in cruise is about 0,5R and 0,8L, there is a small 0,2L residual
Now the true rudder trim deflection should stay between +/- 1,5 degrees, otherwise maintenance has to work again
So the acceptable values are between 2,3L (0,8+1,5) and 1R (1,5-0,5)
Those values has nothing to do with the indication. The point is that there may be a difference from the real trim value by some defined amount
This amount shows that for some reason, the aircraft is trimmed more to the left, always
Regarding the FCOM and the trim, what it says there is that the aircraft when flying should have (theoretically) zero rudder trim input. With this in mind, when it is trimmed, it should be at zero. Because the average value in cruise is about 0,5R and 0,8L, there is a small 0,2L residual
Now the true rudder trim deflection should stay between +/- 1,5 degrees, otherwise maintenance has to work again
So the acceptable values are between 2,3L (0,8+1,5) and 1R (1,5-0,5)
Those values has nothing to do with the indication. The point is that there may be a difference from the real trim value by some defined amount
This amount shows that for some reason, the aircraft is trimmed more to the left, always
In fact, assuming symmetrical fuel loading etc, the rudder is neutral. The left indication bias is due to thermal settling of the structure and trim actuation mechanism at low static air temperature.
Join Date: Jul 2009
Location: London
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Bloody hell, how did you find that out?
Doesn't it say that the actual rudder position is 1.5 degrees left and right. I thought the bias is in the indication.
Join Date: Jul 2009
Location: London
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Why is the permanent offset of indication more to the left than the right?
Hello ExV238 and Owain,
Just to clear up a point raised earlier in the thread, and given that in an untwisted airframe the rudder is neutral: is the fin laterally symmetrical and mounted precisely fore-and-aft, or does the fact that the two large fans are not handed result in any yaw effect that requires compensation?
Chris
Just to clear up a point raised earlier in the thread, and given that in an untwisted airframe the rudder is neutral: is the fin laterally symmetrical and mounted precisely fore-and-aft, or does the fact that the two large fans are not handed result in any yaw effect that requires compensation?
Chris
Join Date: Jul 2009
Location: London
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Just to see how this all fits together, there is a permanent offset of indication to the left because of the cold SAT.
If the average offset is 0.5R and 0.8 left how does that fit in the with 1.5 left and right maximum real deflection and the corresponding maximum value of rudder trim 1R and 2.3L.
Surely max indicated trim would be 1.5L+0.8L=2.3L (that makes sense and that's what's written in the FCOM)
But it doesn't make sense for the right 1.5R+0.5R=2?? (They say 1R)
How does that work?
If the average offset is 0.5R and 0.8 left how does that fit in the with 1.5 left and right maximum real deflection and the corresponding maximum value of rudder trim 1R and 2.3L.
Surely max indicated trim would be 1.5L+0.8L=2.3L (that makes sense and that's what's written in the FCOM)
But it doesn't make sense for the right 1.5R+0.5R=2?? (They say 1R)
How does that work?
Only half a speed-brake
Auto-spellcheck in play? Anyway the're jets, mounted symmetrical, under the wing, exhaust path well below the tail structure... What physical reason do you see for any yawing force?
Join Date: Jun 2011
Location: West of Offa's dyke
Age: 88
Posts: 476
Likes: 0
Received 0 Likes
on
0 Posts
Chris
Good question but it never came up in my career.
Yes, the fin is laterally symmetrical and mounted symmetrically.
Like FlightDetent I can't see any reason for a yawing force if the engines are being operated symmetrically
PilotJames
I haven't read the FCOM so this may be complete nonsense, but if the average offset were between 0.5 and 0.8 left (which is more sensible than 0.5R to 0.8L if it is really a one-way temperature effect) then the 1R/2.3L would also make sense wouldn't it?
Good question but it never came up in my career.
Yes, the fin is laterally symmetrical and mounted symmetrically.
Like FlightDetent I can't see any reason for a yawing force if the engines are being operated symmetrically
PilotJames
I haven't read the FCOM so this may be complete nonsense, but if the average offset were between 0.5 and 0.8 left (which is more sensible than 0.5R to 0.8L if it is really a one-way temperature effect) then the 1R/2.3L would also make sense wouldn't it?
Join Date: Jul 2009
Location: London
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
Chris
Good question but it never came up in my career.
Yes, the fin is laterally symmetrical and mounted symmetrically.
Like FlightDetent I can't see any reason for a yawing force if the engines are being operated symmetrically
PilotJames
I haven't read the FCOM so this may be complete nonsense, but if the average offset were between 0.5 and 0.8 left (which is more sensible than 0.5R to 0.8L if it is really a one-way temperature effect) then the 1R/2.3L would also make sense wouldn't it?
Good question but it never came up in my career.
Yes, the fin is laterally symmetrical and mounted symmetrically.
Like FlightDetent I can't see any reason for a yawing force if the engines are being operated symmetrically
PilotJames
I haven't read the FCOM so this may be complete nonsense, but if the average offset were between 0.5 and 0.8 left (which is more sensible than 0.5R to 0.8L if it is really a one-way temperature effect) then the 1R/2.3L would also make sense wouldn't it?
Maybe it's left (for the right side average left 0.5 and for the left average left 0.8)
Haha
very confusing