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737Andi

Trimming during landing and takeoff

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Hi,

I have a question regarding the trimming function on small and larger aircrafts.

Do B738 or A320 pilots use the trimming function on the yoke or the trim wheel during the final manual landing phase or directly after takeoff before the autopilot gets activated?
I think on a Cessna 172 this standard procedure (please correct me if I'm wrong!).

Thanks!

Best regards Andi

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2 minutes ago, 737Andi said:

I think on a Cessna 172 this standard procedure (please correct me if I'm wrong!).

On Cessna 172, there's a trim position for takeoff and most of PoH mentions "Elevator Trim set to Take off position". Once you know your plane, for most Weight & Balance configurations, you know more or less where to set your elevator trim. For landing, as you should adjust your trim as required during all phase of flight, this includes obviously the final approach, and final legs 😉

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A320 has auto-trim. Just put the nose at the desired pitch angle, center the stick and let the computers do the rest 😁

 

As for the 737, I believe they would trim while hand flying but this would almost certainly be done using the switches on the yoke, unless they had to switch off the electric trim which would only really be done as part of specific emergency procedures

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Rashid Yacine

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One of the captains I fly with is used to trimming during flares.  I personally don't think that's the best technique.  Once you are stabilized on final at Vref/Vref+10 and achieve "2-finger flying", your plane is trimmed properly all the way to touch down and rollout.  As to trimming to rotate, the only time I see that done is by some pilots in sim training with jammed elevator scenario past V1.  Even that, the right action in most cases would be a high speed rejected T/O. 


Jason

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For Boeing:

After takeoff, I don't thingk you need trim before 400AGL, Stick is  sufficient unless mistrimmed or some other problems.

After accerration altitude, you need to lower the nose and trim for higher speed.

On 737 is a little tricky because when you reduce thrust, nose will drop, but then Speed trim system will kicks in to trim up

On 777/787, just Trim down for the new airspeed, FBW will take care thrust, attitude and flaps change.

Trimming during takeoff rotation and landing flare is prohibited by Boring FCTM due to incresed risk of tail strike. And "avoid large trim input" during approach.

For Airbus:

No any trim input needed in air for normal condition.

 

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Trimming during the flare surely means that you were not on a stable approach in the first place??

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Christopher Low

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4 hours ago, Christopher Low said:

Trimming during the flare surely means that you were not on a stable approach in the first place??

No, it doesn't. Trimming during the flare is simply a bad habbit.  During the flare implies that you are already applying back pressure on the stick/yoke, hence you aren't in a trimmed condition in any case. 

Edited by FDEdev

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9 hours ago, C2615 said:

For Boeing:

After takeoff, I don't thingk you need trim before 400AGL, Stick is  sufficient unless mistrimmed or some other problems.

For Airbus:

No any trim input needed in air for normal condition.

Boeing: I don't know what altitude has to with the requirement to trim.  This depends basically only on CG and speed changes. 

Airbus: There are still quite a few A300 and A310 flying 😉 

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Basically the answer is yes. If after takeoff you need to apply control pressure either way to maintain a steady climb angle then you trim accordingly to zero out. Same thing on approach. Just don't do it during rotation or flare.

I always find myself trimming down after takeoff because calculated takeoff trim always pitches up too much and I would have to keep constant downward pressure on yoke if I wouldn't.

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57 minutes ago, Evros said:

Basically the answer is yes. If after takeoff you need to apply control pressure either way to maintain a steady climb angle then you trim accordingly to zero out. Same thing on approach. Just don't do it during rotation or flare.

I always find myself trimming down after takeoff because calculated takeoff trim always pitches up too much and I would have to keep constant downward pressure on yoke if I wouldn't.

Agree... and my way of looking is that trim during flare is similar to trim during turns... don't do it.  Use the control pressures in these cases and during most maneuvers.


Dan Downs KCRP

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Great question by the OP. This layman is certainly learning something: I didn't think anyone would consider trimming during a flare; it is such a transient event lasting only a few seconds. I suppose if someone did trim for the flare then what happens should they desire aerodynamic braking? Direct control column input I guess - flying the nosewheel until it lands rather than rapidly changing the trim.


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So many replies and no one actually answered the question. 

The question was not whether trim is used, the question was whether the piltots use the button on the yoke or rotate the trimwheel itself.

And while I'm not a pilot I would assume that the wheel is only used on the ground while no one is busy controling the airplane. In the air it's probably always the buttons on the yoke that are being used.

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4 hours ago, Farlis said:

So many replies and no one actually answered the question. 

The question was not whether trim is used, the question was whether the piltots use the button on the yoke or rotate the trimwheel itself.

And while I'm not a pilot I would assume that the wheel is only used on the ground while no one is busy controling the airplane. In the air it's probably always the buttons on the yoke that are being used.

I took training in a major airline 767 full motion sim. We used the button on the yoke. 


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7 hours ago, Farlis said:

So many replies and no one actually answered the question. 

The question was not whether trim is used, the question was whether the piltots use the button on the yoke or rotate the trimwheel itself.

And while I'm not a pilot I would assume that the wheel is only used on the ground while no one is busy controling the airplane. In the air it's probably always the buttons on the yoke that are being used.

737's wheel only serves as a backup, 747-787 have no wheel at all.

FBW Airbuses meanwhile, use wheel on ground to set T/O trim, but don't touch it after airborne unless abnromal.

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3 hours ago, Bobsk8 said:

I took training in a major airline 767 full motion sim. We used the button on the yoke. 

It would be difficult to use the trim wheel on the 767 since there isn't one 😉  

On the A320-A380 you can't use the trim button on the side stick because there isn't one. (you don't trim in these aircraft except in the non-normal case)

If there's an electric/main trim (yoke) you use it of course, since you are controlling the thrust levers with the other hand.

Same usually goes for GA aircraft for the same reason. There are some where the electric trim is badly configured and reacts very slow and/or with considerable lag and pilots usually revert to the trim wheel in such cases.

 

Edited by FDEdev

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