What happened
The pilot was conducting a VFR flight, completing the departure, en route, and descent portions without incident. Upon entering the traffic pattern, the pilot turned final and announced his intentions. After observing another airplane holding short of the same runway, the pilot made an additional announcement.
While at an altitude of approximately 100 to 150 feet AGL, the aircraft holding short entered the runway. In response, the pilot executed a go-around, retracting the flaps and landing gear before performing a left 360-degree turn to return to the final approach. The pilot subsequently landed the aircraft; however, during the ground roll, the landing gear retracted. The aircraft slid approximately 100 feet before coming to a complete stop. Following the event, the pilot discovered that the landing gear switch had been left in the up position.
The investigation
An examination of the aircraft was conducted to determine the cause of the gear retraction. Investigators found no damage to the landing gear doors and noted there was no side scuffing on either tire. Furthermore, the investigation identified no preimpact failures regarding the squat switch, the safe gear indication system, or the landing gear horn. The incident resulted in no injuries.