What happened
The accident occurred during a landing phase of flight involving two crew members who were both rated for multiengine operations. One of the individuals was a certified flight instructor (CFI) providing instruction to the other, with the specific goal of upgrading the student to a multiengine instructor rating.
During the approach and landing sequence, the aircraft touched down on the runway with its landing gear in the retracted position. The fuselage and wings sustained contact with the ground rather than the wheels. Neither the pilot flying nor the monitoring crew member realized that the gear had not been lowered or locked into place prior to touchdown.
Findings
The primary factor contributing to the incident was the failure of both pilots to verify the landing gear position before initiating the flare and touchdown. Despite having multiengine ratings, neither individual detected the discrepancy in the gear configuration during the critical final moments of the approach.