Both while spotting and while on the plane myself, I have noticed that dash-8s taxi onto the runway with their spoilers extended, and leave them extended until they begin takeoff roll. I decided to do some research into why this happens, and thought I’d share what I learned here, in case anyone else has wondered the same thing as me.
Dash-8s have a spoiler switch with two settings, TAXI and FLIGHT. Obviously they taxi to the runway with the spoilers in TAXI mode, which disables them completely, regardless of ground speed or throttle position. After the aircraft has been cleared to enter the runway, part of the checklist is to flip the switch into FLIGHT mode. When the spoilers are put into flight mode, they automatically extend, hence why the aircraft taxis onto the runway with its spoilers deployed. FLIGHT mode on the Dash-8 isn’t the same as flight mode on most aircraft in Infinite Flight (and maybe real life, but I don’t know, I have never flown a plane in real life). On the Dash-8, putting the spoilers into FLIGHT mode essentially activates them on an automatic system. The system is set up to automatically deploy the spoilers when the throttle position is less than 12 degrees above idle thrust. The spoilers are set up to extend symmetrically to 75 degrees when the throttle position is below 12 degrees above idle, with weight on the landing gear. While in the air, the spoilers operate asymmetrically. There are two sets of spoilers on the Dash-8, inner and outer. When the aircraft is moving above 140kts, only the inner spoilers are active, and the outer spoilers deactivate themselves. While in flight, the spoilers are acting as roll spoilers. Roll spoilers deflect in harmony with ailerons to enhance roll authority and response, giving the pilot greater control of the aircraft.
To summarize, when you flip the spoiler switch in a Dash-8 into FLIGHT mode, it makes the spoilers act automatically, sometimes symmetrically and sometimes independently, in order to give pilots greater control of the aircraft. The spoilers are extended prior to takeoff because when the automatic spoilers are activated, the aircraft is in a position and configuration where the spoilers are set up to fully extend. If you see the spoilers extend prior to takeoff next time you’re on a Dash-8, no need to worry! As soon as the throttle is pushed past the 12-degree mark, the spoilers will automatically retract.