I'm setting up a scene where the PCs are being chased through some canyons and ravines by some scout troopers on speeder bikes. The PCs will be driving a wheeled buggy vehicle with a rear mounted weapon.

Since the ground is uneven and the gulleys twisting and turning, I think it makes sense for a Piloting (Planetary) check to be made by the PC driver of the vehicle and possibly also the NPCs on the speeder bikes. Page 240 of EtoE core describes this situation. I was going to add setback dice because of the rocky terrain.

What I'm not clear on is whether this check counts as the action for the character for the turn? This isn't such a big deal for the PCs, since the other characters that aren't driving can shoot, but the NPC scout troopers on the speeder bikes will want to shoot at the PCs and their vehicle, and if their only action on their turn is to drive their bikes, it's not going to be a very exciting encounter.

Typically if you roll its an action.

However if its a chase, I'd suggest you check out the dedicated chase mechanic. That should address your issue and allow the bikers to do stuff.

The Action required to make a skill check is only for things that you the GM rule that takes focus and time to perform. If you want to roll for passive piloting, go for it. However...

Making the player roll Piloting constantly is going to drag down the encounter down. What I recommend instead is setting certain setbacks for the whole situation based off the terrain, the constant swooping, and overall stress of not slamming into a cliff side wall. Now you can offer the option to have the character make a Piloting check in order to cancel them out. Then, if despairs are rolled, if an opponent uses a triumph on an attack roll, if plot calls for it, etc now you can have a situation where the Pilot MUST roll to avoid a colision or something like that and it's up to you if that's an action or not.

From Sam in the dev questions answered sticky thread.

The important thing in this situation is to remember that you don't always need to stick with the rules, when doing so could result in a tedious or even ridiculous encounter. If the GM and players like the idea of lots of piloting checks (which increases the odds of failure) then by all means, have them test often. If the GM and players feel that this is slowing down the combat too much, then maybe one piloting check the first time the pilot enters the terrain is enough.