TAC (thrust asymmetry control)

[Guest Chief_Bean]

Hi just a quick question; is thrust asymmetry control implemented in the PSS 777?Thanks, Alex

[Brian Doney 127]

No, it is not.

[Guest NormanB]

Hi Alex,Welcome to the AVSIM forums.TAC was not modelled, no.Edit - beaten by Brian!

[Guest Chief_Bean]

Thanks, it wasn't a major issue i was just inquisitive.

[Brian Doney 127]

Just for informational purposes:When Phil Condit was leader of the 777 design team he said "The pilot must be able to control the aircraft with his feet on the the floor, not with the rudder pedals - no rudder application should be neccessary, and he should maintain stability with just the yoke."To achieve this the aircraft has a wheel-rudder cross-tie and a Thrust Assymetry Compensator (TAC). The wheel-rudder cross-tie moves the rudder (up to 8 degrees of deflection) in response to control wheel inputs. The TAC on the other hand, applies up to 10 degrees of rudder deflection when the thrust from one engine exceeds the other by 10 percent.I can see how this would really be a pain in the --- to model.

[kevinh 409]

Even the dear old 747-200 has a turn co-ordinator which operates rudder as a function of roll rate. This is not new 777 functionality.However the 777 is FBW, and does include features such as automatic elevator control of pitch in a turn to maintain altitude. The pilot only needs to pull on the column for bank angles greater than about 30 degrees. PSS have not simulated FBW so these things are not present.What I'm saying is that on the real 777 all control channels are co-ordinated, not just wheel and rudder. There is no physical cross-tie between them.The 757 and 767 also have thrust asymmetry rudder compensation (as part of the AFCS). The pilot must apply some pedal input to fully trim out the yaw. Not sure whether Level D simulates this on their 767, but I doubt it.The 777 TAC system works by driving rudder trim, not the rudder itself. It operates whether autopilot is engaged or not. It should be perfectly possible to do in MSFS. However the effect is to have no effect, if you see what I mean. Engine failure becomes a non-event. You can simulate it perfectly well by checking the auto-rudder box in FS9. I'm not joking, the effect is the same.Kevin