NTSB Identification: LAX08FA265A
14 CFR Part 91: General Aviation
Accident occurred Sunday, August 10, 2008 in Rock Springs, WY
Probable Cause Approval Date: 07/14/2009
Aircraft: CESSNA R172K, registration: N758NH
Injuries: 3 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The Cessna was on a local solo instructional flight while the Cirrus was on an instrument-flight-rules flight plan and clearance to the airport. The Cessna was maneuvering northwest of the airport, and the Cirrus was descending toward the airport from the northwest. The air traffic controller working the flight cleared the Cirrus for a visual approach and advised the pilot to switch to the common traffic advisory frequency. About 2 minutes and 30 seconds before the collision, the controller advised the Cirrus of an aircraft (the Cessna) at his one o'clock position and 10 miles at 9500 feet mean sea level (msl). The Cirrus pilot responded, "thank you," and there was no further contact with the Cirrus. Radar data indicates that for the next 2 minutes, the Cessna maintained a northeasterly heading and climbed to 9,800 feet msl. About 30 seconds before the collision, the Cessna turned approximately 20 to 30 degrees right and continued on that heading, level at 9,800 feet msl. During this same 2 minute and 30 second period, the Cirrus was descending on a heading of about 130 degrees magnetic. The data depict the two airplanes converging perpendicular to one another and colliding about 5 nautical miles northwest of the airport at an altitude of about 9,800 feet msl, or 3,300 feet above the ground. The wreckage of the two airplanes was intermingled and scattered over an area of about 1,400 feet by 1,500 feet. During examination of the wreckage, transfer marks were identified consistent with the radar-derived collision angle. The Cirrus was equipped with a TCAS-like traffic advisory system that would alert the pilot of transponder equipped aircraft that pose a collision threat within a 0.55-mile radius. Based on the radar data, the system, if turned on, should have generated both an oral and visual traffic advisory starting about 30 seconds before and continuing until impact. It could not be determined whether the unit generated an advisory. It is possible that the geometry between the the system's antenna on top of the Cirrus and the transponder antenna on the bottom of the Cessna prevented the system from generating an advisory, but this could not be confirmed. Both airplanes were operating under visual conditions when they collided.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The failure of both pilots to see and avoid each other's aircraft.

Full narrative available

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