FD off on the A320

[polemic]

I noticed that FCOM has PNF turning both FD off with a TCAS RA, the question I have is do the pilots turn their own FD off for visual app etc I can't find a ref in FCOM but this is how we did it during the Airbus endorsement.

Thanks

[longarm]

Both flight directors should be turned off at the same time by the same pilot. If you are pilot flying and wish to go visual then you will ask the non flying pilot for "flight directors off". Thats how my bunch do it anyway.

[FlapsOne]

It makes not a jot of difference whether they are turned off at the same time or not.

Airmanship would probably dictate that the non handling pilot physically turned them off although I'm sure i could spare the time to do it myself if I were pilot flying

[AlR]

With A/T engaged and F/D's on, pilot must follow the F/D or A/T may give adverse commands to FADEC. To avoid this situation, turn off FD's when not following their commands.

I.E., A/T and F/D's engaged and FCU ALT calling for descent. Pilot is fflying manually and decides to manually level-off without resetting FCU ALT that has open descent selected. A/T is calling for idle thrust to meet open descent command as well as F/D calling for nose down.

However, disregarding their commands, Pilot deciseds to manually level-off. Airspeed will continue to bleed off until Low Speed prot engages.

During RA resolution, chances are you are not going reset FCU commands before manually complying with RA command. Same situation as earlier, A/T will compensate to meet FCU ALT and F/D commands. Which may be the exact opposite of what you desire. So turn off F/D's so A/T revert to SRS sensing and commands.

Doesn't matter if you can fly "through" the F/D commands, what matters is what the F/D's are telling FADEC. If you want to manually fly and disregard the F/D's, then select A/T off any gu manual with the P/L's.

This is one of several posibilities, but message is the same....follow F/D's or turn them off.

[EMER_CANC]

With both FD's Off and the A/T engaged, the active A/T Mode is SPEED. This is the reason I believe that both FDs are to be turned off.

[Dream Land]

My company SOP's were as previously mentioned, the company (major airline) I used to teach for, for instance on a non-precision approach would leave FD's on after the field insight, not necessarily following the FD's, can someone please expand why this shouldn't be done, never created any problems in training. Thanks.

[oldebloke]

READ the accident of the Indian A320 crash #2 since inception.Visual approach,Trainee capt requested F/Dir-OFF,training capt Didn't.Low on approach Trainee notices a/c slowing(not following speed).Calls out to trainer that he called for Directors OFF,trainer infers he should have checked both sides.Airspeed got to stall regime(VLS).Now a/c too low to reach field both Trainee and VLS apply thrust too late(FDR) to avoid terrain.LESSON if one Director on : Auto pilot thinks there is someone there to 'follow' guidance,and won't maintain speed..ERGO both on BOTH off generally at pilots request to NFP..

[FlapsOne]

I must read that report. Got a link?

Normal law protections and/ Alpha floor should have got involved somewhere surely. In any event the thrust should have come up at VLS so there isn't really a stall regime in Normal Law.

FDs off to give SPEED Athr mode is exactly why it is done for a TCAS maneuvre.

[SIDSTAR]

Our SOP is that the PNF switches off the FDs at the first instance of TA in readiness for a possible RA. If no RA results, PNF switches them back on. I must say that the guys like this, as it gets attention early and allows the RA manoeuvre to be conducted smoothly and without hurry.

[Dream Land]

I must be having a brain lock, don't fully understand the rational for the TCAS maneuver, with either TOGA or Thrust LVRS off selected, how will the FD's interfere while either climbing or descending, thanks.

[sabenaboy]

Originally Posted by Dream Land

with either TOGA or Thrust LVRS off selected

In our SOP we keep the A/THR on! Selecting both F/D's off will, as mentioned before, keep the A/THR in basic speed mode. Then we simply pull or push the stick to achieve the desired climb/descend rate, while the A/THR will try to keep the selected speed.
I hope this unlocks your brain!

[Dream Land]

Got it, thanks.