Two air tankers avoid mid-air collision by 400 feet
As two air tankers were descending before landing at the uncontrolled Porterville Airport on July 12 in California, they narrowly avoided a mid-air collision by 400 feet. The aircraft were close to occupying the same space in the sky when the Traffic Collision Alert Device (TCAD) notified the lower tanker crew about the near collision threat from another tanker above. They took evasive action and lived to tell the story. The upper aircraft was a next-generation air tanker that could have been moving at almost twice the speed of the lower legacy aircraft; 330 to 340 knots versus 165 to 200 knots for legacy air tankers.
Next-gen air tankers would include the BAe-146, Avero RJ 85, C-130Q, MD-87, and DC-10. The legacy category has the P2v, S-2T, and Single Engine Air Tankers.
The entire Lesson Learned can be read here. Below is an excerpt:
As the two aircraft were returning to the AAB at the Porterville Airport (an uncontrolled airport) both flight crews made their calls over the CTAF to announce their positions. When the pilots of the Legacy AT heard the NextGen AT announce their position of "15 miles out" at that moment the Legacy AT crew knew they also just announced their position "15 miles out". The TCAD (Traffic Collision Alert Device) simultaneously reported traffic on the display and over the intercom. The NextGen AT then descended directly over the top of the Legacy AT. The Legacy AT flight crew reported that the TCAD displayed 400 feet vertical separation and confirmed it visually. The Legacy AT Pilot-in-Command took action to obtain separation from the NextGen AT avoiding the possibility of encountering wake turbulence. The NextGen AT crew did not receive a resolution advisory (RA) on their TCAS (Traffic Collision Avoidance System) and proceeded to the airport, unaware that an incident had occurred. Both aircraft landed without further incident.
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