During a period of circuit training, the instructor simulated an engine failure after takeoff. The instructor disabled the landing gear warning horn system to reduce noise and to ensure that the student would remember to lower the landing gear, which he did when turning onto base leg. Assessing his approach to be high, the student conducted a go-around and retracted the landing gear. The subsequent circuit was abbreviated due to changing traffic and weather conditions. Final checks were completed without confirmation of landing gear position by either pilot. The aircraft was flared normally, but experienced an extended float, which the pilots attributed to a downwind component. After approximately 500-600m the aircraft settled onto the runway with the landing gear fully retracted.