What happened
Witnesses at the airport observed a twin-engine aircraft entering the traffic pattern to perform touch-and-go landings on runway 28. During the sequence, the airplane experienced a hard landing and porpoised three or four times before departing the right side of the runway.
The pilot-in-command (PIC) reported that a passenger in the right seat, who held an airline transport rating, announced an intention to go around and applied full power. However, the power from the right engine was slow to develop, which caused the airplane to skew off the runway.
As the aircraft was approximately five feet above the ground, the PIC reduced power to the functioning engine. At this time, the airspeed was at or near VMC (minimum controllable airspeed). The pilot reported that the airplane began to roll and directional control could no longer be maintained. In response, the PIC pulled both engines back to the idle position and performed a flare.
Safety message
The pilot-in-command recommended that pilots avoid attempting a full throttle go-around until both engines are confirmed to be operational, or until the aircraft is flying well above VMC.