PMDG 777 FBW and weird Flight Controls behaviour?

[downscc 1,327]

Learning to hand fly the PMDG 777 takes time, it is a beast that is very sensitive to AOA and thrust but thrust is very slow to respond to pilot changes. You have to be ahead of the aircraft.

 

It is probably much easier in a LevelD simulator with servomotors providing force feedback on the controls.  The best hobbyist controller cannot do this.  You experience neutral control forces with the control is at center... this is not realistic in the  least.  PMDG has tried to compensate for this and the result is a hybrid that works when you get used to it but is not intended to be representative of the real experience. It's just not possible.

[skelsey 765]

You experience neutral control forces with the control is at center... this is not realistic in the  least.

Well -- actually, for a jet like the B777 I would suggest it's not too far removed from reality. I'm happy to defer to those with big jet experience, but it is worth remembering that the B777 (and most large jets) is equipped with a Trimmable Horizontal Stabiliser (THS).

 

Therefore, the trim forces/feel is very different to a light aircraft like a C172 which is equipped with trim tabs. When you trim a C172, the tabs hold the elevator aerodynamically in the position you have placed it with the stick: therefore the stick "neutral point" moves.

 

However, in an aircraft with a THS, when the aircraft is in trim the elevators are at the neutral position (i.e. faired with the THS). Therefore, when the aeroplane is in trim, the control column will also be in the neutral position: i.e. centred, just like in MSFS.

 

Of course, the actual stick forces will be significantly higher and the general feel through a hydraulic feel and centring unit will be very different to the springs on a consumer joystick/flight yoke: but the actual principle is, broadly, the same.

[downscc 1,327]

No experience pilot I know is even aware of the yoke position in pitch... we all fly using pressure not movement.  Sorry, I cannot get from a joystick or game yoke controller to the real thing as easily as you.

[skelsey 765]

Absolutely -- as I say, I'm not suggesting that the actual feel of a consumer joystick or yoke is going to be anything like the real thing -- just that in very general terms, the control column on a B777/aircraft with a THS will be at the neutral point when the aircraft is in trim, which is different to an aircraft with trim tabs where (from my own limited experience) it was noticeable when trimming that the stick hadn't moved from where I was holding it but the force I needed to hold it there was removed (which is 100% different to FS).

 

In practice, of course, as you say, with the small control pressures involved and higher out-of-trim forces generated by the feel and centring unit, I don't doubt that in a THS-equipped aircraft the difference (compared to an aircraft with trim tabs) is barely noticeable.

[Alpha Floor 237]

 

 

I've been doing an experiment and it seems pitch correction is simulated, as long as you don't try to be smart and add back pressure yourself.

 

After much experimenting myself I've also come to the conclusion that the FBW is not "perfectly" modeled. But I think this can be forgiven since it's probably impossible to reproduce the real plane's behavior on a home computer with home controls...

 

I try to hand-fly it as smooth as possible, using very little input and just correcting when necessary. A big mistake with FBW is over-controlling.

 

In principle you fly it like a 737 but in practice, when you enter a turn on a 737 you're already adding back pressure to compensate for nose-drop. On the 777 I only add a smooth roll input and see how it behaves. If it holds altitude on it's own then I don't do anything else. If the nose starts dropping then I'll add slight backpressure.

[downscc 1,327]

 

 

I try to hand-fly it as smooth as possible, using very little input and just correcting when necessary. A big mistake with FBW is over-controlling.

 

This.  Don't chase the FD needles, use them as a guide only and pay attention to your aircraft's attitude and speed.  The FD provides a good indication of trend but it is not a game to see if you can keep the square dot on the red bars.

[paulyg123 135]

ok