What happened
A flight instructor and a commercial multiengine student were conducting traffic pattern work and practicing single-engine procedures to prepare for an upcoming checkride. During the flight, the instructor simulated a failure of the right engine and directed the student to execute a single-engine landing. The aircraft touched down with its landing gear in the up position.
The instructor reported that the landing gear had been extended prior to touchdown and that three green lights, indicating the gear was down and locked, were visible before the aircraft reached the ground.