I know the T/O value is calculated by the FMC, but what about the landing? Do I need to worry about that?

Something interesting I noticed is that I can still hear the wheels moving after disconnect the A/P so maybe it's still an automated process.

 

As you can see, I'm a total beginner on this matter. :Loser:

the trim setting is automatic if you have CMD A, CMD B or both, or in CWS modes; if you flight manual you have set the trim. For approach and landing is the same, if ou are flying manually you need manage the trim according the aircraft attitude, normally before landing you set trim up for reduce the rate of descend.

Set it by feel. The sound you're hearing is probably the low-speed trim.

I am guessing the sound he is hearing is when he is in CWS. Its letting him fly manually but trimming automatically.

 

JackColwill

Nope, it's the speed trim. See here:

 

http://forum.avsim.n...opic/361567-THS moves on its own?

 

Basically, the system senses if trim is required and there hasn't been any trim command by the pilots for more than 10 seconds.

 

Regards,

Oli

 

 

Oliver Branaschky

speed trim is an automatic function at low altitude, low speed, and it is avaiable ONLY WITH AP OFF (if AP is ON, AP will trim the plane).

When on ground the trim must be set according to the weights and balance of the plane (as there is no other way to know), in air, the trim is set by feeling as the speed of the aircraft, the fuel and engine power will varies the trim value needed to mantain the aircraft pitched correctly.

How to do? Use the trim to center your joystick, for example, if you are flying leveled and to do that you need to move the joy/yoke a bit aft, just use the trim to let the yoke to be moved to the center, when you are stable, with joy centered (in the real one the center changes with trim) you are trimmed. If you gain or lose speed, change power setting, or fuel is getting burned, the trim value changes and you (or AP, or speed trim) will need to trim again.

After landing, what trim setting do you use? Do you trim it up as far as possible?

No, there is no need for trim after after landing.

Nomally you set it up to 5, in case of icing conditions you should set it to 4 and in case of a night stop with expected icing conditions set it to full nose down.

 

That's what I do in the real 737

Nope, it's the speed trim. See here:

 

http://forum.avsim.n...opic/361567-THS moves on its own?

 

Basically, the system senses if trim is required and there hasn't been any trim command by the pilots for more than 10 seconds.

 

Regards,

Oli

 

 

Oliver Branaschky

 

Amazing, ty.

Answering a few questions here:

First and foremost, you have to understand what trim does. Trim is set to maximize the effectiveness of the surface. In the case of elevator trim, the trim is actually moving the entire horizontal stablizer (tail), to make the elevator more effective. Basically, the way the weight is distributed about the aircraft (center of gravity) affects how much force (elevator deflection) is required to make a pitch change. By adjusting the horizontal stabilizer to have it sit at a different angle, I can use less elevator to affect the same amount of change.

 

You can see the pitch scale at the front of the horizontal stabilizer in this picture (the dark grey arc):

From Wikipedia: http://en.wikipedia.org/wiki/File:Continental_Airlines_Boeing_737-900_N71411.jpg

 

As Andrea mentioned, in the air, you want to "trim to feel." Anyone ever come in on an approach and have to hold back pressure on the yoke the whole way in to descend at the proper rate? Add nose up trim and you no longer have to hold the yoke back. In general, I'll trim it so I only have to hold the yoke back slightly. That way, I'm not having to haul back on the yoke, but I can also release it slightly and get it to descend a little faster if I need to.

 

After landing, you can leave it in the same spot, or you can do a few things:

-Set it at about where you'll think you'll need it on the next leg, or in the middle of the green band

-Leave it where it is

-Set it to a particular value (I think the ERJ flows have you set it at a set value, or at least that's how it's done on the Wilco ERJ)

 

Before takeoff, the reason you look for the calculated value in the FMC is that you can only guess through a calculation. We can't trim to feel ahead of time, so a calculation runs in the FMC to approximate it based on your weight/CG. This is also why you'll often have to trim slightly after departure, even if you'd set it perfectly.

One thing only, if bad wheater is supposed to be before next flight, the stab should be moved to Nose DN to prevent water to stay between elevator and balance panels (that are mounted between elevator and stabilizer). With full nose dn position, water cannot remain trapped this preventing ice formation. and/or corrosion.

Obviously I'm speaking ON GROUND