777 - Auto-trim?

[NWSRG]

Folks,

I know that Airbus have an auto-trim feature so that when hand flying the pilot does not have to trim the aircraft.

On the 777, did Boeing go the same way, or does the pilot still manually trim the aircraft?

[oiseau2]

On the 777 in primary control, the control column pitch trim switches change the trim speed datum in the computers. Once within 5 knots of the desired speed a blip will change the datum to the desired speed.
Sounds complicated but it works and is intuitive in use. Also thrust changes do not need to be trimmed, which with 2 large ones under the wings would be necessary continually.

[CV880]

777 does not autotrim like a fly by wire Airbus when hand flying. There are the usual Boeing dual thumb switches on one horn of each control wheel which alter the trimmed speed ref in the computers rather than directly moving the stab itself as described above.

[gas path]

Just to elaborate a bit....... or confuse;)
On the ground:
The control column controls the elevator and the 'pickle' switches control the stab.
In the air:
The control column, stab 'pickle' switches, and auto pilot all control the elevators with the elevator offload a calculated function from the PFC's of airspeed and roll attitude, active after a time delay moves the stabilizer to null the elevator.

[ARMGAT]

cv 880

Do you agree that when in manual flight and trimmed at a certain speed and following this condition, you rev up the engines there will be no pitch up from the engines but only a subsequent pitch up once the plane accelerates above the previously trimmed speed?

Of course the engine pitch needs to be compensated and the FCC will use Stab and/or Elev or both to do just that.

[CV880]

Sorry ARMGAT. your question/statement is beyond my 777 knowledge. A pilot type may be able to respond.

[Human Factor]

...you rev up the engines there will be no pitch up from the engines but only a subsequent pitch up once the plane accelerates above the previously trimmed speed...

Correct, with the flight control system working normally. If the system degrades to a back-up mode, the pitch-power couple (the pitch up when power is applied) returns and it turns back into a conventional aeroplane.

[ARMGAT]

Is it correct that If you bank withoutpulling back as opposed to a convetional airplane, the FCC will assume that you want to make a level turn and therefore put in a bit of elev/stab automatically in order to do so?

[ratarsedagain]

correct, you don't need to put in any back stick in a level turn in primary mode as long as you are less than a certain amount of bank (about 35 degrees if i remember rightly!)