For Single engine taxi out in the FCOM they mention:
For ENG 2 start, and when taxiing in a straight line:
Maintain taxi in a straight line during at least 5 seconds after selection of the ENG 2 master lever to ON, in order to ensure the PTU auto-test is completed.
What’s the deal with the taxi in a straight line tho? I understand setting the parking brake will inhibit the PTU auto-test but what’s the issue of starting during a turn? Does pressing the brake will affect the PTU auto-test?
Thanks.