hi
i don't know about the c650..but here's how it works on a B722 and it's called the AUTO PERFORMANCE RESERVE..hope it might be of some help
the system is armed when
1- main landing gear shock struts are compressed
2- wing flaps are in the T/O position(5-25 deg for the 722)
3- ALL engines are above approx 73% N1
now if the system detects that one or two engines rpm drops below 6000rpm(approx 73%N1)..the system will signal a solenoid valve in the operating engine(s) fuel control unit(s) to add 1000 lbs of extra thrust
the system will be disarmed after T/O when wing flaps are retracted from the T/O position OR when ALL engines thrust is reduced below 70% N1
however in the event of an engine failure..the system will remain active even when wing flaps are retracted from the T/O position