mustafagander,
Vmcg is defined as the minimum CAS at which when the critical engine is suddenly made inoperative during the take-off run it is possible to maintain control of the airplane using primary aerodynamic controls alone (no tiller control - nosewheel steering) to enable the takeoff to be safely continued using normal piloting skills. This includes:
a. the use of primary aerodynamic controls only (rudder only) since on the ground
b. Rudder pedal force not exceeding 150 f/lbs
c. assuming 7 knts of crosswind from the inop engine side
d. without reducing thrust on the live engine, and
e. landing gear remaining extended.
In addition, the path of the aeroplane at which engine failure occurs to the point at which recovery to a direction parallel to the centre-line of the runway is attained may not deviate by more than 30 ft laterally from the centre-line at any point. JAR25.149(E).
Vmca is the minimum CAS at which when the critical engine is suddenly made inop, it is possible to maintain directional control of the aircraft with:
a. Rudder pedal force not exceeding 150 f/lbs
b. Bank not exceeding 5 degrees
c. Directional Change not exceeding 20 degrees
d. Without reducing thrust on the live engine
e. A/c airborne with little or no ground effect. It may not exceed 1.2Vs JAR 25.149(B) and (D).
Since V1 can never be less than Vmcg, and Vr cannot be less than V1 or 105%Vmca (among other things) it is possible to have Vmcg higher than Vmca in theory, but it should not be more than by a few knots. If anyone knows of such cases and why/ how, I am always eager to learn.
Cheers