Incident Overview
A near collision occurred between Pan American Flight 511 and a Cessna 172 or 182 approximately 10 nautical miles east of Houston/Hobby Airport. The event took place while the airliner was inbound on the Gilco One Standard Terminal Arrival Route (STAR) at an altitude of 6,000 feet and a speed of 250 knots.
Sequence of Events
Pan American Flight 511 had been cleared by Houston Approach Control to descend and maintain 6,000 feet. While traveling westbound on the arrival route, the flight engineer sighted a Cessna aircraft ahead. The captain initiated an evasive left turn as the two airplanes converged. Flight 511 passed the Cessna with an estimated separation of 100 yards.
The Cessna was on a west-northwest course at 6,000 feet near the Airport Radar Service Area (ARSA). The pilot of the Cessna was not in radio communication with Approach Control, and Houston radar was not receiving a transponder reply from the Cessna. The upper limit of the ARSA was 4,000 feet mean sea level (MSL).
Air Traffic Control Aspects
The captain of Pan American Flight 511 reported the near collision to the controller. The controller acknowledged the report and stated that he was aware of the traffic but did not issue an advisory to Flight 511. Radar data confirmed that the unidentified Cessna had been maneuvering in a busy area approximately 10 miles east of the airport, along the Gilco One arrival route, without a transponder display.