APU operation during low vis Takeoff

[Adsto]

Hello all,

Am trying to find out why NG/BBJ operators have the APU running during low visibility takeoffs. I can't find a regulatory requirement and am wondering whether it is done because we can, and it doesn't otherwise affect system operation. If in the event of an engine or IDG failure, the APU is available for quick selection.

Can anyone help out with more information. Any regulatory requirements?

Thanks,