To the ERJ and 757 guys
 

We were sitting in the Q in-line in EWR and were wondering what the 4 Yellow strakes under the tip of each wing are for on the ERJ?

Also on most jets, just happened we saw on a 757, what is the door that opens just under the captains side rear elevator, is it a back up air vent for the APU? I am pretty sure the one on the FOs side above the elevator is.

thanks ! If you got any Q400 questions Ill try to answer in return !

That is part of the pressurization system. The one on the FOs side is the APU inlet door.

ERJ = "Vortilons"

Create an aerodynamic fence at lower airspeeds/high AOA to help prevent spanwise flow.

As what Swaayze said. In other words, the vortilons act as fancy vortex generators to re-energize and re-direct the airflow over the ailerons at low speeds high AOA.

Side note: the ERJ has only ailerons for roll control, the spoilers are purely for speed brakes and ground spoilers.

At XJT we have an alternate name. The Beaumont rake.

They're missile pods for war time.

Possibly they are the outflow valve (lower left aft side of the fuselage) and the APU intake (upper right extreme aft)

thanks for the answers, yeah i figured they had something to do with vortex generator-ish traits, but looked way different - interesting !

hahah classic

when the Q400 takes the runway, how come the spoilers always go up until they start rolling??