3D helis main blades are the same profile on top and underside so they fly inverted using the +12 -12 degs of pitch so when inverted you move throttle (which is pitch as the rpm is fixed by a governor in the ESC) down and heli will climb move stick up heli comes down , the quad with variable pitch does the same thing fixed rpm pitch changing , if you flip a normal quad it will power drive into the ground , the Swiss drone being a CP heli collective pitch heli same as 3D heli should be able to fly inverted if you can set up +12 -12 degs of pitch