Sign in to follow this  
mrvoyager

Autotrim behavior

Recommended Posts

Why can't the 777 have a similar autotrim behavior to the MD11? In the MD11 handflying interaction is so much better, I get smooth transitions from climb to cruise, smoother turns, smoother descends, the autotrim is smooth, steady, and stable in the MD11, and the odd thing is that its a much older aircraft. I know, the flight characteristics are not the same, but still I think the 777 should have a smoother autotrim so that handflying would be better. If it was done with the MD11 then it can be achieved with the 777.

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

Google C*U

I'm not an expert, I'm just saying, autotrim could probably be much better, smoother.

Share this post


Link to post
Share on other sites

Google "C*U Control law."

 

The former just gives gibberish results.

Is there a way I could configure the pmdg autotrim parameters to make it smoother or at least try?

Share this post


Link to post
Share on other sites

In a 777 you trim for speed and not pitch. Let's say you hold the trim knob on the yoke up (just like increasing the upwards pitch on non-fly-by-wire aircraft) for half a second - this results in a 5 knot decrease, which is achieved by a slight pitch increase. It's just different than what you'd find in an Airbus, a MD-11, which isn't fly-by-wire but has some fly-by-wire elements or your regular 737, 757 or Cessna. Personally I don't really like how it works in the sim either, since I don't always get 30 frames on landing and the fly-by-wire doesn't seem to catch up to my inputs as fast as I'd like.

 

If you want to get used to it, do some circuits at different landing weights  and you'll grease every landing.

Share this post


Link to post
Share on other sites

In a 777 you trim for speed and not pitch. Let's say you hold the trim knob on the yoke up (just like increasing the upwards pitch on non-fly-by-wire aircraft) for half a second - this results in a 5 knot decrease, which is achieved by a slight pitch increase. It's just different than what you'd find in an Airbus, a MD-11, which isn't fly-by-wire but has some fly-by-wire elements or your regular 737, 757 or Cessna. Personally I don't really like how it works in the sim either, since I don't always get 30 frames on landing and the fly-by-wire doesn't seem to catch up to my inputs as fast as I'd like.

 

If you want to get used to it, do some circuits at different landing weights  and you'll grease every landing.

I've been doing circuit after circuit trying to figure it out, but its just unstable, I never achieve smooth transitions, I don't even know what it is. I think its that the autotrim reactions are just not in sync with the aircraft aerodynamics, it needs some further refinement. I actually preferred the first version that came out, no autotrim, but I can't get it back.

 

I simply hate it to be honest, I don't even fly the airplane that much because I mainly just do circuits, I usually don't do routes. So I mainly fly the 737 and a320, but I really love the advancement made with the 777, I like how it looks a lot, the other simulations, but its just this annoying autotrim, its just not smooth, and I expect smoothness when it comes to such an advanced and large aircraft. The jerkyness I have to engage in to stabilize the airplane sometimes feels like I'm flying some faulty cessna.

Share this post


Link to post
Share on other sites

Well, I don't think it's that bad. Maybe something is wrong with your control setup. Could you make a video, which shows your problem? 

 

And to be honest, the 777 does not require a lot of trim on final, once you've trimmed it around Vref it should stay there, from then on work with power and pitch adjustments to hold your desired speed and maintain the glidepath. 

Share this post


Link to post
Share on other sites

I've been doing circuit after circuit trying to figure it out, but its just unstable, I never achieve smooth transitions, I don't even know what it is. I think its that the autotrim reactions are just not in sync with the aircraft aerodynamics, it needs some further refinement. I actually preferred the first version that came out, no autotrim, but I can't get it back.

 

I simply hate it to be honest, I don't even fly the airplane that much because I mainly just do circuits, I usually don't do routes. So I mainly fly the 737 and a320, but I really love the advancement made with the 777, I like how it looks a lot, the other simulations, but its just this annoying autotrim, its just not smooth, and I expect smoothness when it comes to such an advanced and large aircraft. The jerkyness I have to engage in to stabilize the airplane sometimes feels like I'm flying some faulty cessna.

 

Hi, Francisco,

 

I think you may have a problem with your setup.  Your joystick trim buttons or whatever keys that are set for trim may be giving too many commands.  For example FSX may be set to repeat quickly the trim up and trim down commands when you hold the buttons down.

 

There is a good deal of discussion in the PMDG 777 Introductory Manual about trim and fly-by-wire.

 

I don't have a particularly high-powered system but I haven't experienced any issues with the trim.  It is not supposed to be completely auto when flying manually.  In fact the early 777 versions had a mistake that gave too much autotrim when flying manually.  They completely redesigned the fly-by-wire system.

 

If this was a problem with the PMDG 777, there would be many complaints showing up in this forum.

 

If you search "fly by wire" and "trim" on this forum you should find a great deal of discussion about how the trim is supposed to work, including by RW 777 pilots.

 

Mike

Share this post


Link to post
Share on other sites

Well, I don't think it's that bad. Maybe something is wrong with your control setup. Could you make a video, which shows your problem? 

 

And to be honest, the 777 does not require a lot of trim on final, once you've trimmed it around Vref it should stay there, from then on work with power and pitch adjustments to hold your desired speed and maintain the glidepath. 

 

Hi, Francisco,

 

I think you may have a problem with your setup.  Your joystick trim buttons or whatever keys that are set for trim may be giving too many commands.  For example FSX may be set to repeat quickly the trim up and trim down commands when you hold the buttons down.

 

There is a good deal of discussion in the PMDG 777 Introductory Manual about trim and fly-by-wire.

 

I don't have a particularly high-powered system but I haven't experienced any issues with the trim.  It is not supposed to be completely auto when flying manually.  In fact the early 777 versions had a mistake that gave too much autotrim when flying manually.  They completely redesigned the fly-by-wire system.

 

If this was a problem with the PMDG 777, there would be many complaints showing up in this forum.

 

If you search "fly by wire" and "trim" on this forum you should find a great deal of discussion about how the trim is supposed to work, including by RW 777 pilots.

 

Mike

Yeah guys, I am afraid to say this, but I think I simply had to calibrate my joystick. I think this was the problem, that I was moving the stick and it was making the elevators jump and this was interacting with the autotrim, hence no smoothness. It is not perfect, but the dynamic improved a lot. I am still trying to get the hang of manually flying this bird, but its a lot better now, I am starting to enjoy it.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this