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NTSB: limitations of ‘see and avoid’ concept factor in two fatal midair collisions
16 November 2016
Illustration of approximate collision of airplanes (NTSB)

Illustration of approximate collision of airplanes (NTSB)

The U.S. National Transportation Safety Board (NTSB) issued a Safety Alert to pilots with suggestions on what they can do to reduce their chances of being involved in a midair collision.

Recent accidents showed the limitations of the “see and avoid” concept of aircraft separation, NTSB analysis showed.

On July 7, 2015, a Cessna 150 that had just departed from Moncks Corner, South Carolina, and an F-16 Air Force fighter jet on a training mission collided. An air traffic controller advised the F-16 pilot that the Cessna was a potential traffic conflict. The F-16 pilot was not able to visually acquire the Cessna until it was too late to avoid the collision. The two occupants of the Cessna were killed; the F-16 pilot ejected and survived. The NTSB determined that the probable cause of the crash was the air traffic controller’s failure to provide an appropriate resolution to the traffic conflict.

On August 16, 2015, a North American Rockwell Sabreliner inbound for landing at Brown Field Municipal Airport in San Diego and a Cessna 172 that was practicing landings at the same airport collided. The four occupants of the Sabreliner and the sole occupant of the Cessna were killed. A cockpit visibility study revealed the fields of view of both pilots were limited and partially obscured at times. The NTSB determined that the probable cause of the accident was the air traffic controller’s failure to properly identify the aircraft in the pattern and to ensure control instructions were being performed.

The NTSB said that contributing to both accidents were the inherent limitations of the “see and avoid” concept of traffic separation. These limitations, combined with errors by the air traffic controllers, resulted in the pilots’ inability to take action to avoid the collisions.

The Safety Alert highlights the value of traffic avoidance technologies to pilots as an aid to detecting and avoiding other airplanes in flight. Such technologies also serve as another layer of safety in the case of air traffic control errors, such as those referenced in the two accidents above.

In addition to issuing the Safety Alert, the NTSB made recommendations to the Federal Aviation Administration and the three companies operating federal contract control towers in the U.S., asking them to brief air traffic controllers on the errors in the two midair collisions and to include these accidents as examples in initial and recurrent training.

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