Sikorsky UH-60A N160AQ accident near San Diego, California

Probable cause

The failure of the crewmembers of the second helicopter to maintain visual separation with the first helicopter while complying with the LC controller’s instruction to go around. Contributing to the accident were the nighttime conditions and the lack of a safety alert from the controller to either helicopter.

NTSB analysis

While conducting nighttime training at a tower-controlled airport, two helicopters were involved in a midair collision. A common practice at the airport was for the air traffic control tower (ATCT) local control controller (controller) to control helicopter operations on a non-movement portion of runway 26L called the underrun.

The first helicopter to arrive was cleared for the option to land on the runway 26L underrun, at their own risk, but remained under control of the controller. The first helicopter flew one traffic pattern and then returned to the underrun and landed. The second helicopter arrived at the airport about 8 minutes later, and was cleared by the controller for the option to land on the runway 26L underrun. After the second helicopter crew reported that the first helicopter was in sight, the controller instructed them to “maintain visual separation” from the first helicopter, which the crew of the second helicopter acknowledged.

While the first helicopter was on the underrun’s surface area preparing to take off, the second helicopter turned to the base leg of the traffic pattern. The controller believed that the second helicopter may have turned early and would possibly overfly the first helicopter, so he told the first helicopter that he needed him to take off; the pilot replied that they were taking off. The controller then made two radio calls to the second helicopter, one not received, and the other garbled. The controller then instructed the second helicopter to perform a go-around on the north side of runway 26L. While the pilot of the first helicopter was performing the takeoff, he saw the second helicopter overhead and attempted evasive action. While maneuvering, the main rotor blades of the first helicopter struck the second helicopter’s stabilator, which substantially damaged the main rotor blades of the first helicopter and the stabilator of the second helicopter. Both helicopters then landed on the airfield and shut down.

The takeoff instructions for the first helicopter, followed by the go around instructions for the second helicopter, combined with the night conditions, likely created a scenario where the second helicopter crew lost visual contact with the first helicopter and overtook it from overhead. The controller was concerned that the second helicopter would overfly the first helicopter but did not issue a safety alert. The lack of a safety alert likely prevented the flight crews from understanding how close the helicopters were to each other, as well as their urgent need to take action to avoid a collision.

Text from the NTSB. Open the NTSB docket for WPR23LA045 for the full record.