this plane does have a problem on taking off

it's more related to TRIM than flaps or anything else ::)
try setting your elevator trim so that the plane pulls UP on takeoff
this happens because the trim is NOT set to neutral when you load this particular aircraft
the plane tends to pul itself DOWN when rolling down the runway

if the runway is long enough, you might be able to pull it up without correcting the pitch trim

i have set two of my joystick buttons to control the pitch trim, so i can easily keep it at neutral (it varies depending on your airspeed)
you're talking about the Flacon 50 by Yannick Lavigne, right?
