I'm probably late to the party on this, but finally figured out what pickle refers to - it means to drop a bomb or fire a missle. The pickle button is the big red button rather than the trigger that drops the bomb or launches the missle.

http://www.christianfighterpilot.com/fighterpilotspeak.htm#Pickle

https://forums.ubisoft.com/showthread.php/325021-What-does-Pickle-mean-with-regard-to-bombs-pls-Forums