A320 Flight Director off on after startup
 

flight directors come ON at FMGC startup.
Is it necessary to turn it off until final alignment and MCDU setup is completed?
and also do so using both hands almost simultaneously to turn it on?
I've noticed this habit.
thanks many

Different opinions ... Don't think it's an airbus requirement. Current employer always turn them both off after landing. Don't know why. Previous employer - we never touched them unless visual approach etc.

Some people think its a good reset of system. I don't think it's necessary.

Good practice using two hands.... Both off or both on! Guess its why 380/350 only has one button for both FDs.

IIRC, there was an OEB regarding this topic. It was fixed in our fleet about 5 years ago - may be a function of habit.

I am not sure is a good practice :8

DSC-22-30-20 P5/6
Note: If AP/FDs are OFF, and FD2 then FD1 are engaged within 180 ms (one computation cycle),
a flip flop of master FMGC may occur.

Quite - you don't want to flip flop your master FMGC now, do you?

Wow! Does that mean that having lost A/THR channel 1 you could "flip flop" to FMGC 2 as master and regain CAT3B capability? ;)

Hi,

I believe some do confuse Both FD's OFF and ON together with doing them simultaneously.It should not be done simultaneously for the reason Tiennetti has mentioned.
However they should be both ON or both OFF together.Has an impact on Auto Thrust modes.One of the reason for A320 accident at Bangalore if I remember correctly.

so there really is no need to touch them...

You'll get CAT 3 Single as you will have to use AP2 to have A/THR channel 2 as master.

Now I don't fly an Airbus, and I understand the both on/off principle, but why did Airbus decide to do that?

If the PF decides to hand fly (no AP, A/T), wouldn't it be wise for the PM's FD to be up so he could more effectively monitor the PF's performance?

the FD is closely linked to the autothrust logic.
FCOM recommends to follow the flight director exactly no matter which mode its on. then its both ON or both OFF.

I understand that, but isn't it possible to have the FMA show:

___ | GS | LOC

In that case, the AT would be off, and the PF would be free to fly and not have to worry about the AT doing something inappropriate?

Hi Check Airman,

The use of only 1 FD whilst the PF is handflying FD OFF can be quite misleading. You will be most of the time out of the bars as the sensitivity of the machine regarding corrections is obviously much higher than the human's one. I believe that the PNF has already his job in monitoring the parameters regardless of the FD indications. You can't monitor something that the other pilot is not following, i.e. FDs orders.

Check Airman.
It is not possible to get that FMA because when you switch off both FD's the FMA will show SPEED in the first field.

Yes it is manual thrust!

Thanks guys. Here's a question for you. What if the PF turned off his FD, you'd expect to see

SPD | GS | LOC

What would happen if the A/T was disconnected? Does it matter if the AP is engaged or not?

yeah you could fly like that also.

Hi Check,

you can either be with ATHR on in speed mode (as in your example) or simply OFF. It doesn't really matter. You can be AP ON for the approach and manual thrust if you're not "satisfied with the ATHR performance"

Cheers.

Thanks for the information guys.

FD engagement
 

All said about the flip flop is correct....you will risk inhibiting the engagement of your A/THR and vertical modes which is confusing and inconvenient and even sometimes hazardous considering that this will happen during flight when you are already under a load and maybe even in a critical phase....
as for the flight director engagement, it should not be done untill the preparation is complete and all the take-off speeds have been inserted because on many occasions, when the FD is engaged prior to inserting the speeds, the managed mode for take off speeds is not considered, and you will not see your speeds on the PFD in magenta, instead you will only see the number 100 in blue, or whatever speed you have selected on the FCU also in blue.......that can only be rectified by toggling your FD off-on again.