The way I remember it it´s just to look into "Options" then "Controls", you pick the plane and under the controls you´ll find "Start Left/Right Engine" and "Stop Left/Right Engine"
In the "Doc" folder of the main game´s folder you´ll find the manual too.
Give it a squeeze, it´s good stuff.
Hope this helps.
"It takes forever +/- 2 weeks for the A-10 to get anywhere significant..."
"Ha! If it gets him on the deck its a start!"
"What people like and what critics praise are rarely the same thing. 'Critic' is just another one of those unnecessary, overpaid, parasitic jobs that the human race has churned out so that clever slackers won't have to actually get a real job and possibly soil their hands."