Beech F90 N124BK incident near Idaho Falls, Idaho

Probable cause

The partial retraction/collapse of the main landing gear during the landing roll for undetermined reasons.

NTSB analysis

According to the pilot, he lowered the landing gear handle during a straight-in approach to a planned full-stop landing. Subsequently all three green "gear safe" lights illuminated, and the red "gear unsafe" light terminated its illumination. The pilot executed a normal landing touchdown on the main landing gear; however, during the landing roll the gear warning horn sounded, the red "gear unsafe" light illuminated, and the airplane began to settle toward the runway. The pilot then executed a go-around, during which the tail contacted the runway. The pilot continued the go-around, lowered the gear manually, and made an uneventful landing. A postaccident inspection revealed that for reasons that were unable to be determined, the weight of the airplane, which should have been carried by the over-center gear down locks, had been carried by the gear actuator system instead. This led to the tripping of the circuit breaker protecting the actuator electrical system, and ultimately to structural failures within the mechanical portion of the actuator system, which allowed the landing gear to partially retract.

Text from the NTSB. Open the NTSB docket for WPR10IA482 for the full record.