When (in the real world) are pre-takeoff checks done -- ie in a C172 running the engine, checking for magneto drops etc.Do you do it at the holding point -- and if so what if you're in a queue for takeoff, surely you don't hold up all the traffic behind you. You can't be moving because most checklists include having the parking brake on. Also in a more complicated aircraft the checklist is quite long. Any ideas?

Takeoff checks are always done at the hold short line, even in traffic. This includes the runup and engine checks. In order to prevent your prop blast(GA Aircraft) from hitting traffic behind you, angle your tail into the grass and away from the planes behind you. As for larger aircraft, I am not completely sure, but they probably perform the checks as they taxi to the active runway. Hope this helps!

Actually, there's usually a small "runup" area near the hold short line especially for this. Performing the checks right at the hold short line could potentially block other traffic. Transport category aircraft usually perform the checks while taxiing.---For every action, there is an equal and opposite government program.

Interesting thanksI presume you only ask for take off clearance once you've done them. And presumably big jets can do these checks without putting the brakes on!

On the heavy metal, all T/O checks are done on the run as it were - from start up, push back and while taxiing with frequent cross checks between the captain and F/O. Many times I have watched OR been up front when an aircraft has swung onto the active and is ready to go without a short hold. This helps ATC and stops a backlog of other a/craft especially when airlines are doing their uymost to keep to schedule.Ian