Summary
During a visual flight rules approach to Runway 30, a scheduled commuter flight collided with a truck and trailer on the runway. The pilot attempted a go-around but the aircraft's belly struck the trailer, causing the airplane to descend out of control and sustain structural damage.
Incident Details
The airline transport pilot activated threshold warning lights for vehicle traffic on a roadway crossing the runway threshold by using radio microphone clicks. Gates designed to work with the lights to block vehicle access were inoperative, a condition the pilot was aware of. On final approach, the pilot observed a large truck and trailer stopped near the landing threshold. As the aircraft neared the runway, the truck began moving across the threshold area. The pilot initiated a go-around, but the airplane's belly contacted the top of the trailer, leading to an uncontrolled descent onto the runway.
According to the truck driver, he saw the flashing red warning lights but noted the gates were not closed. After waiting about 45 seconds and observing no landing traffic, he drove onto the road in front of the threshold, where he felt the aircraft impact the trailer and saw it hit the runway.
The trailer was approximately 45 feet long and 13 feet tall. The Federal Aviation Administration (FAA) Facility Directory/Alaska Supplement recommends pilots maintain a minimum threshold crossing height of 25 feet.
Investigation Findings
The National Transportation Safety Board (NTSB) investigation revealed that the gate system had been out of service for more than one year due to budgetary constraints. No Notice to Airmen (NOTAM) was issued regarding the inoperative gate system. The FAA-certificated airport is owned and operated by the State of Alaska. Per the Airport Certification Manual, the airport manager is responsible for inspecting, maintaining, and repairing airport facilities to ensure safe operations, as well as for publishing NOTAMs concerning hazardous conditions. A review of annual FAA certification and compliance inspection forms from the preceding 10 years revealed no discrepancy listed for the inoperative gates until 16 days after the accident.
Probable Cause
The NTSB determined the probable cause of the accident was the pilot's failure to maintain clearance from a truck while landing, and the vehicle operator's decision to ignore runway warning signals. Contributing to the accident was an inoperative vehicle gate system and the failure of airport management to adequately maintain the gate system and issue a NOTAM.