Re: Bypassdoors on Dash 8 100
Not flown the 100 - but as far as I know they are the same as the 300 (which I have flown). You have two buttons in the cockpit just to the left of the centre of the main instrument panel labelled "Engine Intake Bypass Door n" (n=1 or 2). To open the doors push them in! The idea is to stop unwanted solids (e.g. ice) accumulating at the back of the plenum chamber. Normal procedure is to open them in icing conditions, although some airlines leave them open all the time as there is little penalty in doing so and it's one less thing to forget!. They are electrically actuated, operated from the 28 VDC system. They are also heated (by 115 VAC) to prevent ice accretion although this only activates if the OAT is less than 15 degress C. Finally, if they are closed and something heavy hits them , there is a breakable diapragm and shear door built into the front face of the bypass door to ensure such objects are ejected anyway and don't enter the rotating engine!
Hope this helps
Pilot Paul