I have just started flying A320.
- What are the procedures for a single-engine taxi?
There are lots and lots of details to this:
We can't do single engine taxi OUT above 75500kg
Or with contaminated taxiways.
We start no 1 (because it pressurizes green system which = brakes and n/w steering), turn Y ELEC Pump on,leave APU on and bleed on and taxi out. All checks such as flight control can't be done until we've started eng 2. Y Pump off, confirm sufficient bleed press and eng 2 lvr idle, then start no 2.
you need both engines running at idle or near idle for at least 2 mins before applying takeoff power, otherwise you get a CTR TNK FEEDG on the t/o roll.
For single engine AFTER landing, it's much simpler - make sure APU is on, switch Y ELEC pump on (avoids running PTU) then switch 2 off. Once on stand with off, switch Y pump off again. Must have engines near idle for 3 mins if reverse thrust was used - very rarely nowadays.
- Is the APU left on for the entire taxi?
Yes - obviously you need APU whenever both ENG Generators aren't online.
- Is there a certain duration which engines must be spooled up for before they are TOGA/FLEX-rated?
see above. If the engines have been shutdown for more than two hours, they both need to run for at least 5 mins. So basically, they need to be well and truly started by the time you reach the holding point.
- Does keeping the second engine off really save that much fuel considering the running of the APU and the additional thrust required to move the aircraft?
Depends how heavy a/c is and how long the taxi is - if it's a relatively light aircraft at somewhere like EHAM with really long, boring, tedious, arduous taxi then it could be a good idea- APU burns quite a bit less fuel than ENG1!
However, I do find th a/c quite a bit more cumbersome with only 1 eng when a/c is fairly heavy, and also I find that the procedures involved give you even more to do on the taxy out. i don't like doing it, but do at places like AMS or CDG. it's at PF's discretion.
should you need any more info, pm me. i'm happy to help.
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