On August 24, 2016, about 1830 central daylight time, a Beech E-55, N855T, impacted the runway surface during a gear-up landing on runway 17 at Sheppard Air Force Base/Wichita Falls Municipal Airport (SPS), Wichita Falls, Texas. The airplane sustained substantial damage to the bottom fuselage structure. The flight instructor and a commercial rated dual student pilot were uninjured. The airplane was registered to and operated by Cobra Kai Inc (dba Cobra Kai Flight Academy) under 14 Code of Federal Regulations Part 141 as an instructional flight that was operating on an instrument flight rules flight plan. Visual meteorological conditions prevailed at the time of the accident. The flight originated from Kickapoo Downtown Airport, Wichita Falls, Texas at 1609 and diverted to SPS. The flight instructor stated that during an approach for landing, the landing gear selection handle was placed into the gear down position, and "immediately" he and the duel student pilot noticed electrical smoke and fumes, but there was never a fire. The battery and alternator switches were selected to the off position to vent the cockpit. The flight instructor and the pilot restored electrical power and saw the landing gear up and down position indicator lights were not illuminated, and the landing gear circuit breaker was tripped. They were unable to fully extend the landing gear. The manual landing gear crank handle did not engage and spun freely in both directions and they were unable to fully extend the landing gear. They then performed a gear-up landing on runway 17. Post-accident examination by the Federal Aviation Administration of the main landing gear retraction actuator assembly revealed a broken snap ring within the manual crank extension housing that allowed the actuator worm gear to reposition itself beyond the actuator worm sector travel limits. There was no airplane maintenance record showing that the landing gear actuator assembly had been repaired/overhauled. The airplane had a total time of 6,184.5 hours. According to the Baron 55 and 58 Maintenance Manual, section 5-10-00- 601, dated April 1, 2015, TIME LIMITS/MAINTENANCE CHECKS, TIME LIMITS INSPECTION/CHECK, A. Landing Gear states that the actuator assembly is to be overhauled or replaced every 2,000 hours for gray or green colored assemblies. The assembly that was examined was green colored.