Beech 35-A33 N433JC and Robinson Helicopter R22 BETA N7508Y accident near Antioch, California

Probable cause

The failure of both pilots to see and avoid the other aircraft during cruise flight. Contributing to the accident was the failure of air traffic control personnel to issue the helicopter pilot with a prompt and appropriate alternate course of action upon receiving a conflict alert.

The failure of both pilots to see and avoid each other during cruise flight, which resulted in a midair collision. Contributing to the accident was the failure of air traffic control personnel to issue the helicopter pilot a prompt and appropriate alternate course of action upon receiving a conflict alert.

NTSB analysis

The helicopter and airplane collided midair. Both aircraft sustained minimal damage during the impact but substantial damage during the subsequent forced landings. The airplane pilot was performing a local flight and was not in contact with air traffic control (ATC) before the collision. The helicopter pilot was receiving visual flight rules flight following services from ATC throughout the flight.

The helicopter pilot transitioned between two ATC sectors before the accident. On multiple occasions, the controllers for each sector misidentified the last three digits of the helicopter's call sign. Additionally, the controller in the accident sector issued a traffic advisory using the wrong call sign. Further, an aircraft with the same last three digits as the helicopter's incorrect call sign made radio contact with the controller shortly before the collision, which increased the confusion.

Audio data revealed that the air traffic controller provided multiple traffic advisories to the helicopter but did not issue an alternate or immediate course of action in accordance with ATC procedures despite the fact that the aircraft's converging flightpaths had triggered the radar conflict alert system. Radar playback also revealed that, at that time, the controller was receiving a visual alert on the radar console. This alert was also observed by a controller in an adjacent approach sector who called the radar assist controller warning of the threat. The assist controller responded, "yeah, we're givin' him traffic." A few seconds later, the radar targets merged.

The helicopter pilot stated that she received and complied with the traffic advisories by performing a visual scan but that, based on her communications with the air traffic controller, she did not perceive the situation to be urgent. Radar data revealed that the helicopter descended 600 feet before the collision but that the pilot did not inform the air traffic controllers about the descent. Further, as the airplane got closer and the traffic advisories were issued, the helicopter pilot began turning north, which brought the helicopter directly into the path of the approaching airplane while simultaneously placing the airplane behind her immediate field of vision. Shortly after, she sighted a silhouette of the airplane and propeller at her 4-o'clock position. She performed an evasive maneuver to the left but then felt the helicopter being struck.

Neither the airplane pilot nor the occupant observed another aircraft near the airplane before the collision. Although the airplane pilot was not receiving traffic advisories from ATC, it was still the pilot's responsibility to maintain a proper visual lookout to avoid other aircraft in the area. The helicopter's left navigation light was inoperative when tested after the accident; however, this most likely did not affect the outcome because the left side of the helicopter would not have been visible to the airplane pilot at any point during the flight.

Text from the NTSB. Open the NTSB docket for WPR12LA109 for the full record.