Why we start ENG NO 2 during airplane engine start up A320 family?

Question

Why we start ENG NO 2 during airplane engine start up A320 family?

Answer 1

engine 2 powers the major equiptment,

Answer 2

Mostly so the airplane will fly, but I don't think you are asking why we start engine #2...but here is some insight as to the SOP's at most US carriers.  The procedure is to start engine #1 and turn on the Electric Yellow Hydraulic Pump to taxi and when close to takeoff we turn the Y-Electric pump off and start engine #2.

Answer 3

Yet as stated in the previous answer...it is the systems that run off the given engine, it makes operation safer. This way you do not have to rely on the hydralic accumulator to keep the parking brake working.  And, some A/C engines start easier based on their location to the APU.

Answer 4

Engine 2 powers the yellow hydraulic system, which controls the  brakes.