A320 SE Taxi and 2nd Start
 

Our FCOM warns against applying brakes during the second engine start while single-engine taxiing. There is no explanation given.

Is this an old caution for the older BSCU's? Can anyone explain why this is a valid caution?

Cheers!
AKAAB


:confused:

Perhaps it can be distracting doing two things at the same time, haha

I always start both BEFORE I taxi.

I would guess it is to do with the PTU... as the PTU senses the rise in the new operating engine hydraulic system pressure it will disengage, and at the point of disengagement there MAY not be full hydraulic system pressure available for brakes for a brief perid of time. I think, anyway, just an educated guess... we certainly don't apply any brakes on shutting one engine down taxying in; in that case if the PTU didn't kick in then brakes would be on the secondary system.

Don't understand the SOP of taxying out on one engine, though, but mine is not to reason why....

Squid

It comes down to managing fuel costs. 30-40 mins taxi time on one engine versus two can save a lot of fuel costs. With the US airline industry bleeding cash it's a simple way to safely cut some costs.

The yellow electric pump is ON during single engine taxiing (#1 engine running) - so the PTU theory might not apply since the yellow system is already at normal hyd pressure.

As far as I recall, it has to do with electrical transients when the second gen comes on line.

Not sure if that is still a problem with the latest BSCUs.