You could start engine one, shut down 2, turn off the Aux hyd pump and brake switch. Then start 2 again.
It’s a possible solution. But I don’t think you need to shut down #2. For this to work you need enough pressure in the hydraulic system. So you need to:
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Start engine #1, this engine will provide pressure to the system.
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As correctly stated by lolz3346630:
Be sure that you disengage the prop brake while condition lever #2 is on the feather position
otherwise the prop break cannot be disengaged.
- Try to disengage the prop break. If it doesn’t work it’s because you still don’t have enough pressure. Increase the thrust of #1. This can be checked by inspecting the upper panel in the
HYD PWRsection. If it is illuminated asLOPRyou should add more thrust (but not too much, you don’t need to go over the gust lock).
I absolutely don’t know if this is realistic. But this is how I understand the logic of the ATR implementation.