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achutchison

777 pitch trim - Am I missing something?

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For the longest time, I had thought my issue was just a poor simulation of the fbw trim, however as I started to watch footage of others flying the 777 more closely, I realized that I might have a problem on my end. What is happening is that I find the aircraft unflyable with out the "show fbw trim" setting enabled. The trim forces are jerky, unpredictable, and non fluid and almost feel like the autopilot has been engaged in the pitch axis to maintain the fbw trim airspeed. I read the introduction manual regarding the trim logic before and after sp1 and I cant understand why others are not having this issue. The trim is supposed to feel just like any other airplane (the 737 and 747 trim beautifully for me) right? Please let me know what I could be doing wrong or what I dont understand. I am running FSX 777 version 1.10.7025 with fsuipc. Thanks.

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For the longest time, I had thought my issue was just a poor simulation of the fbw trim, however as I started to watch footage of others flying the 777 more closely, I realized that I might have a problem on my end. What is happening is that I find the aircraft unflyable with out the "show fbw trim" setting enabled. The trim forces are jerky, unpredictable, and non fluid and almost feel like the autopilot has been engaged in the pitch axis to maintain the fbw trim airspeed. I read the introduction manual regarding the trim logic before and after sp1 and I cant understand why others are not having this issue. The trim is supposed to feel just like any other airplane (the 737 and 747 trim beautifully for me) right? Please let me know what I could be doing wrong or what I dont understand. I am running FSX 777 version 1.10.7025 with fsuipc. Thanks.

 

Hi Aidan,

 

Sounds like a controller configuration issue.  How do you have the elevator trim setting configured?  I use FSUIPC for most controls, but I have the up and down trim set through FSX to two buttons on my joystick and it works fine.  Not jerky at all. 

 

Mike

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I've got it configured the standard way with 2 buttons on my joystick. I noticed these problems before I got fsuipc. Nothing changed in that regard since fsuipc was installed. I also noticed that on the 777 and the 747 the yaw damper doesn't do a great job coordinating the airplane especially at low speeds. It seems like it waits for me to finish rolling into the turn before applying the coordinating rudder movements. I wonder if there might be a problem with a software config. I've reinstalled many times too.

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For the longest time, I had thought my issue was just a poor simulation of the fbw trim, however as I started to watch footage of others flying the 777 more closely, I realized that I might have a problem on my end. What is happening is that I find the aircraft unflyable with out the "show fbw trim" setting enabled. The trim forces are jerky, unpredictable, and non fluid and almost feel like the autopilot has been engaged in the pitch axis to maintain the fbw trim airspeed. I read the introduction manual regarding the trim logic before and after sp1 and I cant understand why others are not having this issue. The trim is supposed to feel just like any other airplane (the 737 and 747 trim beautifully for me) right? Please let me know what I could be doing wrong or what I dont understand. I am running FSX 777 version 1.10.7025 with fsuipc. Thanks.

 

I know exactly what you are talking about. I am using FSUIPC too, but like you I cannot find any difference in behavior with or without it.

My experience is that you need to trim slowly. if you keep the trim switch pressed in any direction, it will first appear that nothing is happening. So you keep pressing, and all of a sudden the airplane jerks up or down by a large factor.

If you are out of trim, make small adjustments on the trim switch, wait for the changes to settle in, then trim further.

It's different compared to the NGX which reacts quicker and more direct, but then in the 777 all inputs need to go through the FBW computers.

 

Nothing to do with controller calibration IMHO.

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I find it hard to believe that my sim is working properly. It can't possibly have been intended for the trim and coordination to be so jumpy and sloppy?

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I find it hard to believe that my sim is working properly. It can't possibly have been intended for the trim and coordination to be so jumpy and sloppy?

 

Have you tried "blip trim" (see intro manual p. 171)?  Please specify exactly how you have trim set up.  On mine, I use FSX Buttons/Keys for elevator trim, and the repeat sliders for both up and down are all the way to the right (maximum).  I do use FSUIPC for other controls, but not this one.  If you are using FSX, try removing the controller buttons from FSX and setting them in FSUIPC.

 

Also, just to cover all bases:

 

Regarding yaw damping, by any chance do you have autorudder checked (it should be unchecked)? 

 

What version of the 777 is installed ?

 

Mike

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It's different compared to the NGX which reacts quicker and more direct, but then in the 777 all inputs need to go through the FBW computers.
 

 

Having flown in a real life Delta 777 simulator recently, I can attest that the PMDG flight model accurately models the pitch trim. 

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If you want to know everything about the PMDG T777 from a real world 777 captain,

buy the the AIRLINE2sim PMDG Boeing 777 cadet training.

(I have no any commercial interest in this airline2sim video's)

Regards

Jovabra

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Since we are on the topic of trim, is it me? but I can't trim the plane in a turn.  The blue tick mark will not move when in a decent banked turn.  I need to level off before the "blue tickey thingy" moves

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No, the 777 trim does not feel like the trim in a 737. It's completely different. I've had a discussion about this with a RW pilot who transitioned from the 737NG to the 777. Having flown both types (well, a 737CL) in a level-D sim I can also personally confirm that. 

The 777 has a so called trim for speed - by pressing the trim knob on the yoke (1 second equals 5 kts) you select a speed, which the aircraft's FBW then pitches to and tries to hold it. You can't really trim the 777 in short bursts like you could in the 737, with it's servo-mechanical trim.  The 777 can still be flown quite naturally, it's only a slight adjustment to make, really. If are really having problems with trimming the aircraft properly, you should take a look at your hardware controls setup. Do you have buttons assigned for your trim, are those trim commands representing the 1sec = 5kts bahaviour correctly? 

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I have a trim wheel configured directly through FSX controls and it's nearly impossible to use. For some reason it works in reverse (if I turn wheel for nose up, 777 trim goes for nose down and vice versa).
And this happens only to 777. All other planes behave as expected. 

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The first question that arises is why you are trying to trim a 777 with a trim wheel to begin with? This ain't a Cessna and PMDG's simulation surely wasn't designed to be compatible with trim wheels. 

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Trim issues have been smoothed out with a new joystick (elevator noise didn't agree with the fbw computers) but i'm still having issues with the yaw damper at slow speeds. The issue is most apparent when rolling out of a turn that the yaw damper has gotten comfortable with and doesn't seem to want to return the rudder to its original position. Also when rolling into turns, the bank angle must be held for about 5 seconds before the yaw damper will coordinate the plane. I can see how this might feel nice in the real thing, but with a twisty joystick it's not so good. Is this normal yaw damper logic, or is there a problem? (I have the same issue in the 747 but not the 737) Thanks!

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