Clandestino;
Quote:
Originally Posted by
PJ2
or one can move the thrust levers forward (out of the autothrust regime) and obtain instant thrust.
Originally Posted by Clandestino
I see what you mean, but taken out of context it can be a bit misleading. To clarify: you can get increase above thrust commanded by ATHR by putting TLs between CLB and TOGA detent. However there's nothing instantaneous about it: CFM56s have lots of inertia, V2500s even more so and 60 tons of aeroplane is not to be regarded lightly. Burst of power at last second might save botched landing in Twotter, chances of same procedure succeeding on 320 are extremely slim. Heavier the aroplane more the forethought is required to fly it.
On the contrary, the procedure works well if and when a slight increase in energy is all that is required. Of course, the procedure would necessarily have to be permitted by your FCOM and that is what provides the context for understanding and use.
Normally, if the ATHR is engaged, the speed will not decrease below Vls but there may be circumstances (quartering, slightly increasing tailwind) which may require a small, momentary increase in thrust and setting the thrust levers above the CL detent is one way - disconnecting and flying manual thrust all the way to touchdown is another.
Not all flight crew training manuals describe the procedure nor is it necessarily an SOP for all operators. While the procedure is a valid one, each airline publishes its own SOPs using Airbus publications as final guidance. In other words, I shouldn't think that an airline would permit something not permitted by Airbus but may restrict their own crews from something permitted by Airbus.
Here's an
example of a description of the SOP described above:
If all thrust levers are set to beyond the CLB detent, when A/THR is active, the flight crew manually controls thrust to the Thrust Lever Position.
The FMA displays MAN THR in white, and the A/THR is armed.
As a reminder, LVR CLB flashes on the FMA. This technique is most efficient, when the aircraft speed goes significantly below the target.
When the aircraft speed or acceleration is satisfactory, the thrust levers should be brought back to the CLB detent.
This re-activates the A/THR.
SPEED DROP ON APPROACH: RECOMMENDED RECOVERY TECHNIQUE
Note: When using this technique during approach (e.g. to regain VAPP), the thrust levers may be moved past the CLB detent, but not beyond the MCT.
In most cases, it is not necessary to go beyond MCT, as the PF could inadvertently advance thrust levers all the way to the TOGA stop, and thereby engage go-around mode.
Meikleour, superb, helpful comments.
PJ2