N93124Cessna 152 · 1981

On February 1, 2013, at 0805 central standard time, a Cirrus model SR22 airplane, N247RB, and a Cessna model 152 airplane, N93124, collided inflight about 13 miles west-southwest of Easterwood Field Airport (CLL), College Station, Texas. Both airplanes were able to land at CLL following the collision. The Cirrus SR22 sustained substantial damage to the upper cockpit fuselage structure and the commercial pilot sustained minor injuries. The Cessna 152 sustained minor damage to the right main landing gear assembly and the flight instructor and the student pilot were not injured. The Cirrus SR22 was owned by a private individual, but operated by the Cirrus Aircraft Corporation as a demonstration airplane. The Cessna 152 was owned and operated by the Texas A&M Flying Club. Visual meteorological conditions prevailed at the time of the accident. Both flights were being conducted under the provisions of 14 Code of Federal Regulations Part 91. The Cirrus SR22 departed Austin Executive Airport (EDC) at 0748 and was en route to CLL. The Cessna 152 departed CLL at 0744 for a local instructional flight.According to a statement provided by the Cirrus pilot, after climbing above the departure airport's traffic pattern altitude he engaged the autopilot system and continued direct toward CLL under visual meteorological conditions. The cruise portion of the flight was at 3,500 feet mean sea level (msl). The pilot reported that as the flight approached CLL, with the autopilot system engaged, at 3,500 feet msl, the windshield suddenly imploded from an apparent impact with an object. His initial thought was that the airplane had collided with a bird because he had not received any alerts from the airplane's traffic advisory system nor did he see another aircraft. He subsequently recovered from an unintended descent before continuing direct toward CLL and declaring an emergency with the tower controller. The pilot reported that he had not established radio contact with the tower controller before the inflight collision. A normal landing was subsequently made on runway 16 without further incident.

The Cessna flight instructor reported that the local training flight was with a primary student on her second instructional flight. The flight consisted of basic attitude flight maneuvers, which included level and climbing turns, climbs and descents to predetermined altitudes, and maintaining level flight while tracking a course. The flight instructor stated that as they were climbing to 3,500 feet msl, while maintaining a southeast heading, they felt an impact and heard a loud bang. He reported that the impact originated from the right side of the airplane, aft of the main cabin. The flight instructor noted that there were no apparent flight control issues following the collision and that he observed no damage to the right wing. Shortly after the collision, his student saw another airplane in a rapid descent at their 10 o'clock position. The flight instructor entered a descending left turn to follow the other airplane. Shortly thereafter, the flight instructor heard another airplane declare an emergency on the tower frequency due to an imploded windshield. He noted that they were monitoring the tower frequency before the collision, but had not established radio contact with the tower controller. He turned in the general direction of CLL with the intention of returning to the airport, while continuing to monitor the tower controller's communications with the other aircraft. The flight instructor noted that at some point he told the tower controller that they had hit something and were returning to the airport. The tower controller requested that the Cessna stay west of the airport while the other aircraft landed. After the other airplane had landed, the tower controller transmitted that the other airplane had tire marks on its roof and requested that they make a low approach to verify the condition of their landing gear. The flight instructor stated that he then observed that the right main landing gear wheel had separated from the airplane. His student, seated in the left seat, confirmed that the left landing gear and wheel appeared undamaged. After informing the tower controller of their damage, they were asked to perform a low pass and then to circle the airport until emergency equipment was in position. After circling the airport several times the flight instructor made an uneventful landing on runway 22.

Global positioning system (GPS) data was extracted from the Cirrus airplane and the Cessna flight instructor's portable GPS receiver. The extracted GPS data was reviewed using software that displayed the individual flight paths in a simulated three-dimensional environment. After departure, the Cirrus proceeded direct toward CLL at a cruise altitude of 3,500 feet msl. The plotted GPS data indicated that the Cirrus SR22 was established on a 080 degree true course at 3,500 feet msl for about 14 minutes before the collision. After departure, the Cessna proceeded northwest of CLL where it completed several maneuvers that were consistent with basic attitude flight instruction. About 90 seconds before the collision, the Cessna was in a climbing left turn from a west-southwest course to the south-southeast. The plotted data established that during the 70 seconds before the collision, the Cessna maintained a 160 degree true course. While on the south-southeast course the Cessna continued to climb from 3,100 feet to a maximum GPS altitude of 3,573 feet, which was recorded about 12 seconds before the collision. The Cessna subsequently descended about 60 feet during the 12 second period before the collision. The calculated descent rate, during the 12 second period before the collision, was about 300 feet per minute.

According to available flight path data, at 0805:47, the two airplanes collided at 3,500 feet msl. The calculated angle between the each airplane's flight path was about 80 degrees at the time of the collision. During the 70 seconds before the collision, the Cessna's relative position to the Cirrus flight path averaged 27 degrees left of course (11 o'clock position). Conversely, the Cirrus's position relative to the Cessna flight path averaged 72 degrees right of course (between 2 and 3 o'clock position).

A review of air traffic control (ATC) radar data revealed no transponder beacon returns associated with the Cessna after its departure from CLL until 2 minutes 34 seconds after the collision. During the same time period, raw radar returns, also known as primary radar returns, were recorded by the ATC radar sensor that closely matched the flight path as recorded by the Cessna flight instructor's portable GPS receiver. Primary radar data does not include any altitude or beacon code information. The beacon code and encoded altitude information is received by ATC radar when the airplane transponder is turned on and selected to transmit. According to radar data, after the collision, at 0808:21, the ATC radar sensor began receiving transponder beacon returns from the Cessna that included a 1200 beacon code with associated mode-C altitude data. A reinforced beacon return was received for a remainder of the Cessna flight path. Further review of the ATC radar data established that there were reinforced beacon returns for the Cirrus airplane throughout its entire flight.

The Cirrus was equipped with a Garmin model GTS 800 traffic advisory system, which actively interrogates other nearby aircraft transponders to provide the pilot with relevant traffic advisories. According to manufacturer documentation, the Garmin GTS 800 only displays traffic targets from those aircraft that have transponders that can be interrogated. In the event when a target airplane has its transponder turned off, selected to standby, or is malfunctioning, the system will not generate a traffic advisory. Additionally, the Garmin GTS 800 operating manual notes that pilots should remain vigilant for non-transponder equipped aircraft or aircraft with unresponsive transponders.

When presented with a summary of the ATC radar data, the flight instructor acknowledged that he likely departed with the transponder off, or in the standby position, and then subsequently turned it on following the collision. Additionally, postaccident testing of the Cessna's altitude, static, and transponder systems revealed no anomalies that would have precluded their normal operation.

The Cirrus was equipped with a Recoverable Data Module (RDM) that recorded, among other flight parameter data, when a traffic advisory was issued. A postaccident data extraction revealed that a traffic advisory was issued shortly after takeoff, while the Cirrus was on initial climb from the departure airport. No additional traffic advisories were issued for the remainder of the accident flight.

At 0753, the CLL automated surface observing system reported the following weather conditions: wind calm, visibility 10 miles, sky clear, temperature 7 degrees Celsius, dew point 3 degrees Celsius, and an altimeter setting of 30.35 inches of mercury. According to astronomical data, at the time of the inflight collision, the location of the sun was between 8-10 degrees above the horizon and about 115 degrees east of true north.