auto thrust is too aggressive when hand flying

[sakukio]

When I do hand-flying with auto trust , the auto trust will move forward and back aggressively.
This leads to constantly changing pitch attitide and then the pitch attitude is not stable when I do hand-flying.
Just have little question.  Is it normal condition?

[Martin Baker]

My understanding is that the 747 isn't to be hand-flown with the autothrottle engaged for that very reason. M

[skelsey]

As Martin says - that is exactly why Boeing do not recommend the use of autothrottle in manual flight in the 747-400 .

[Britjet]

As the comments above indicate - yes.
Take the autothrottle out first.
Peter.

[Avi]

Take the autothrottle out first.

In many videos I saw on YouTube I heard the pilots take the A/P out first and only then the A/T (I guess if it happens in a second or two it doesn't matter).

Cheers,

[emerydc8]

I always do it at the same time, but if you disconnect the A/P first and make any pitch changes, the A/T is going to change too, then you're going to have to readjust the power. Easier to disconnect both or disconnect the A/T first. You are usually going to want the power setting that the A/T was doing when you disconnected it. Move the pitch with the A/T connected and it will change that power.

[ahaka]

Should the use of manual thrust also apply for takeoff and manual flight during climb?

[emerydc8]

Should the use of manual thrust also apply for takeoff and manual flight during climb?

No. According to the FCTM, it is okay to use the A/T for takeoff and climb in manual flight.

Autothrottle Use
Autothrottle use is recommended during takeoff and climb in either automatic or manual flight. During all other phases of flight, autothrottle use is recommended only when the autopilot is engaged.

[Jeroen Hoppenbrouwers]

... and this probably is because during takeoff and climb, the thrust is fixed (mostly THR REF, sometimes less, like during TO/GA it's 2000 fpm). With a fixed thrust, the A/T basically isn't active. So no pitch deflections.

Hoppie

[emerydc8]

Good point. Though, even hand flying at cruise altitude is harder with the A/T engaged. Minor pitch changes have significant effects on the throttle movement with the A/T engaged. Taking the A/T out of the picture when hand-flying at cruise makes it much easier.

[Jeroen Hoppenbrouwers]

By the way interesting that the AP/FD and the AT apparently can work together while they are not implemented by the same box. Does anybody know whether they actually talk at the low level required to anticipate and counteract box-induced oscillation?

Hoppie

[Hardy Heinlin]

( General topic on "hand-flying" now split into new thread: http://aerowinx.com/board/index.php?topic=5013.0 )

[Hardy Heinlin]

Does anybody know whether they actually talk at the low level required to anticipate and counteract box-induced oscillation?

I think there is no direct crosstalk in terms of elevator and thrust lever motion commands. But there are sensor states and mode transition phases in which elevator and thrust lever commands assist each other indirectly just by knowing what the current aircraft guidance task is.

Examples:

• When altitude-on-elevator and airspeed-on-thrust swap their tasks to airspeed-on-elevator and altitude-on-thrust, there is the so-called gamma phase that first focusses on the flight path angle (gamma) which requires both vertical speed and airspeed to be mixed-controlled by the elevator while the thrust smoothly changes from airspeed control to fixed thrust control (reference limit, or idle, or a specific initial vertical speed). This mixed gamma phase is over when the target airspeed is acquired (if it went off anyway) and when the target thrust is reached. No direct crosstalk in this example, but the mode change per se and the sensor data lead to interdependent assistance.

• In SPD mode, the thrust increase rate is higher than the thrust decrease rate. There is no direct crosstalk to the elevator pitch control, yet these rates assist the pitch control, especially in turbulence. When gusts modulate the airspeed by, say, +/-10 knots, the average airspeed thrust setting won't be in the middle between -10 and +10 knots, but more on the good side because every negative gust will be compensated by a quick thrust increase, and every positive gust by a slow thrust decrease, i.e. positive compensation always lags behind negative compensation, leaving the average thrust more on the positive side. In this example, just the sensed airspeed variation alone leads to interdependent assistance. Not a direct crosstalk, but an indirect and desired effect anyway.


|-|ardy