View Full Version : A320: Unreliable Speed, how to accelerate and clean up?

21st Nov 2016, 15:57
Hello Guys,

I was recently checking the procedure for unreliable speed in the QRH for aircraft not equipped with the BUSS and assuming you takeoff conf 2, and at 1000 feet you have complete loss of IAS. Ok memory item done, you are now level off with conf 2 at let's say 4000 feet. Now if you decide to divert ( assuming weather is bad at departure airport) what will be your technique to accelerate and clean up the plane? Or even if you could come back to departure airport, how will you descend with conf 2?
Surprisingly the QRH only provides pitch and N1 table for climb, cruise and descent only in clean configuration!?!

I was thinking maybe set Thrust climb, pitch 5 with conf 2 for like 10 seconds then select flaps 1, watch out for VLS and set the pitch & n1 according to the table in QRH for conf 1 and same thing for clean configuration... But that just an idea, don't know how good or bad it is. I would prefer to know what Airbus will recommend us to do, or if none what would be your techniques?

Thank you.

21st Nov 2016, 18:56
In your case safety is affected so:
Memo items, Flight path stabilisation, then ADR check procedure.
If all sources affected, and assuming you want to divert:
1) Set Climb thrust and set flaps 1 after 2-3 seconds. Continue acceleration.
2) As the pitch reduces below the setting for 1 and while keeping level path, clean up.
3) Set pitch/thrust for clean conf.

For the other question...As a rule of thumb zero pitch for descent will not stall your aircraft with flaps extended. But it may be a lot. Check with GPS alt.

But I would configure long final with conf3 gear down and establish the glide...being 4000-5000ft, no problem at all.

And this is only if you lose the speeds before clean up. There is no reason for climbing more than 5000-6000ft if terrain is flat. All other cases you are already with clean aircraft.

21st Nov 2016, 18:57
As far as I know:

CONF 0,1,2,3 => maintain CONF // CONF FULL => CONF 3
The level off table has a grid for slats/flaps extended in the different configurations. You use this to troubleshoot in the present configuration. So there is still no need to accelerate.

With the troubleshooting completed you can identify the ADR that is still reliable and with that one proceed to flap retraction and navigation if deemed necessary.

21st Nov 2016, 23:01
Retrofitted aircraft (and all the new) have the BUSS system which is based on AOA. This discussion is without this one