Handling dynamics with redesigned FBW Sytems

[scandinavian13 5,192]

 

 

Good to know. The only serious fault I get with the FBW is a strong pitch up after banking level after a turn (less than 30 degrees bank). Everything goes OK entering the turn, altitude is maintained correctly without back pressure in the turn, but it goes a bit haywire in pitch as I roll level. Is this one of the known problems? I think I've seen it mentioned on the forum.

 

I'd submit a ticket just so they have more information about it.

 

 

 

Trimming is more difficult in the 777X than it should be

 

...based on?

 

(Since I know you're a sim tech, I know it's entirely possible that you have sim evidence to back that up.  If that's the case, I'd pass your info/evidence along via a ticket.)

[kevinh 409]

I'd submit a ticket just so they have more information about it.

OK, I'll do that. There are a couple of other non-FBW issues I need to raise too while I'm at it.

 

...based on?

 

(Since I know you're a sim tech, I know it's entirely possible that you have sim evidence to back that up.  If that's the case, I'd pass your info/evidence along via a ticket.)

It's based on 777 pilot comment on this forum, 777 cockpit DVDs (notably the Cathay Pacific 777 which goes deep into the FBW system) and the EVA Air 777 youtube video. The FBW is intended to make things easier, not harder. We all know the problem with trimming in FSX (lack of feedback forces) but the way the 777 FBW simulation is currently set up it's harder than in conventionally controlled sims like the NGX. It's noticeably more difficult. Boeing certainly would not have designed the real 777 FBW this way, and the FAA would not have certified it, if the FBW made things harder to do.

 

BTW, I'm not a sim tech, I'm a sim engineer. Technicians maintain sims, engineers design them. Subtle difference (but I know you didn't mean anything by it).

[Swen 1]

So you don't get force feedback, but i must push or pull my yoke. I need force for this. And if i don't need force and the yoke is neutral position, the bird is trimmed well.

[hmsdreadnought 12]

I've flown a sim: 

 

1. Trimming is intuitive and not challenging on the real jet

2. The plane goes where you point it - maintaining proper pitch in a turn is far easier in the real airplane.  This may be a function of controls - my PFC yoke is fairly stiff in the elevator axix so it feels like real work to keep the nose up.  But I don't remember having to think about it in the sim.

2. The plane does not jerk around or throw it's nose up suddenly - and I'm not a pilot so it had lots of opportunity on the take offs to exhibit this kind of behavior. It's behavior is very smooth and refined.

3.  United pilots are trained to use trim extensively on final approach for minor adjustments to movements of the FD - at least this is what the instructor pilot (lead instructor on the 777 for the airline) said..  So, I'm not sure that it's realistic to expect to not have to trim a lot on final - esp with the engines spooling up and down to try to keep VREF+5.   I think this is where the PMDG bird  (the 200) excels - I've had no trouble landing it with and without AT on.  It's the other stuff that are far harder than they are on the real plane.  I don't have the 300 so I've not experieced the nose up behavior at flare.

 

I said it in an earlier post.  The real plane is ridiculously easy to fly in terms of handling.  It goes where you point it.  The sim's FBW sim feels like it's always catching up, is not smooth. But it still feels like an early beta of the FBW system to see if the concept would even work or not.

[whoispankaj 51]

Yeah its strange that some of them have issues and some dont..I have had no issues with trimming the plane for level flight both with A/T on and off

[scandinavian13 5,192]

 

 

BTW, I'm not a sim tech, I'm a sim engineer. Technicians maintain sims, engineers design them. Subtle difference (but I know you didn't mean anything by it).

 

Gotcha - thanks for the clarification!

[gnomegemini 7]

I flew yesterday with cheat mode activated. I experienced that the blip trim is obligatory. One example:

FBW speed at 180kts

Aircraft speed at 176 kts

 

Now I want to trim further down to get some negative VS (I alway fly via trim). When I do trim the blip function snaps in and the FBW trim speed goes to 176 and then while pressing trim down it increases. What I expect is that it is not going back to 176 but increasing it's speed from 180 upwards.

 

Sry for bad english. Difficult to explain.  :unsure:

 

My thoughts in german, maybe someone understand it and can verify:

Wenn ich bei 176FBW trim speed und 180kts nach vorn trimme, erwarte ich, dass trimspeed nach oben geht. Aber es geht erst auf 176 zurück um dann nach oben zu gehen.

[Swen 1]

Yes, i can confirm this... This is very strange... I just use a T Flightstick.X and Saitek Yoke. Seems that Flightstick make more this issue as my Yoke...

[777simmer 117]

I flew yesterday with cheat mode activated. I experienced that the blip trim is obligatory. One example:

FBW speed at 180kts

Aircraft speed at 176 kts

 

Now I want to trim further down to get some negative VS (I alway fly via trim). When I do trim the blip function snaps in and the FBW trim speed goes to 176 and then while pressing trim down it increases. What I expect is that it is not going back to 176 but increasing it's speed from 180 upwards.

 

Sry for bad english. Difficult to explain.  :unsure:

 

My thoughts in german, maybe someone understand it and can verify:

Wenn ich bei 176FBW trim speed und 180kts nach vorn trimme, erwarte ich, dass trimspeed nach oben geht. Aber es geht erst auf 176 zurück um dann nach oben zu gehen.

I would like to help/confirm but do not understand what you mean in English nor German!

Sorry.

 

In English you say FBW speed is 180 in your example.

In German you say FBW speed is 176?

 

Which is it now?

 

Your English is not so bad.

You just have to describe more carefully and exact.

 

Same as when you say; "when I trim further down....."

What down?

Nose down?

Speed down? (which is slower and thus nose up)

FBW trim ref speed down? (slower FBW speed also mean nose goes up).

 

Just say if I push the trim switches fwd/aft....or something like that.

[gnomegemini 7]

Okay. I have FBW trim speed set to 180kts and flying 176kts. So trim is slight nose down. Now I want to trim further nose down so I push the trim button. But instead of increasing from 180 to let's say 190 it's blipping back to 176 and then increasing.

 

What I expect:

aircraft @176 and fbw @180 kts

trimming further nose down so fbw should increase to let's say 190 or so.

 

What I get:

aircraft @176 and fbw @180kts

now trimming and fbw speed is "blipping" back to 176 and only then is increasing while I press the button.

 

So the "blip" trimming is occuring everytime even if I press the button for more than 1 second but it shouldn't.

 

Edit: Following older PMDG tips I have the repeat rate of the trim buttons at 50%.

[Swen 1]

I understand this... It's easy to say:

 

If you trim away and you are on 180, you hit more times trim up and then the fbw jumps forward to 190 than back to 180 and then jumps up to 190.

Same happens if you trim down. That is exactly what i show in my video. I trim only in one direction and the trim jumps back to the set speed before.

 

I can understand that, if you trim jump to the speed of 180 from 170 that the blip catch 180... But i don't understand that it jumps back to 180 if you will catch 190.

 

You go up and it shortly jump down if you. If you go down it jump short up.

 

If and after this back jump and in the right direction the jump is to big to get a sensitive trimming for 190. And this is execlty the point, why that is so hard to trim out this bird on speed.

[virtualstuff 758]

I understand this... It's easy to say:

 

If you trim away and you are on 180, you hit more times trim up and then the fbw jumps forward to 190 than back to 180 and then jumps up to 190.

Same happens if you trim down. That is exactly what i show in my video. I trim only in one direction and the trim jumps back to the set speed before.

 

I can understand that, if you trim jump to the speed of 180 from 170 that the blip catch 180... But i don't understand that it jumps back to 180 if you will catch 190.

 

You go up and it shortly jump down if you. If you go down it jump short up.

 

If and after this back jump and in the right direction the jump is to big to get a sensitive trimming for 190. And this is execlty the point, why that is so hard to trim out this bird on speed.

 

Well it seems with FSUIPC assigned trim it's working fine local here only with default FSX assigned I see and noted the same behaviour...

So via FSUIPC assigned trim it's trimming this bird as easy as a 737 :-) and fly without hands and autopilot lol

Null zone pitch needed some tweaking 2.5% in my case....

 

Ps. great work on SP1 from PMDG this bird left the long parking from the hangar and is in the virtual skies with a great blue dress :wub:

[Swen 1]

 

Well it seems with FSUIPC assigned trim

 

You mean that FSUIPC are the problem for trimming? I nothing setup anything in FSUIPC for trimming and get this effect with different devices. Saitek Yoke and Flightstick X.

[virtualstuff 758]

You mean that FSUIPC are the problem for trimming? I nothing setup anything in FSUIPC for trimming and get this effect with different devices. Saitek Yoke and Flightstick X.

Swen in my case it's FSX default which gives the problem as you described above and assigning via FSUIPC solved the issue.

Of course in combination with the null zone adjustment in the FMC ;-)

[gnomegemini 7]

Have to say I've not installes FSUIPC at all!