TELCAP practice focus
Mid-air collision prevention is a useful TELCAP topic because it requires precise discussion of separation, communication, workload and safety barriers. A strong answer should avoid blaming one person before an investigation is complete and should explain how several defences can fail.
Historical cases
Mid-air collision is a special term for an accident involving two aircraft during the flight. It is the worst case of safe separation loss. Many mid-air collisions include ATC-related, communication, surveillance or coordination factors. During the soviet period about 10 mid-air collisions took place. The most significant cases are shown below. 09.09.1976 Antonov-24 and Yakovlev-40 collision over the Black sea. Air traffic controller of Krasnodar ATC Center had been working for 6 hours without any rest with high workload. One of the aircraft under his guidance, Yak-40 on its way from Rostov-on-Don to Kertch, was maintaining FL 5700 m, but after passing one of the waypoints he was supposed to be instructed to change its flight level either to 5400 m or to 6000 m, but controller forgot to change FL, so Yak-40 remained at the level of opposite direction, which then became occupied by another passenger liner — An-24.Two aircraft collided over the sea, killing 70 people on board. 11.08.1979 Tupolev-134 collision over Dneprodzerzhinsk. Two Tu-134 aircraft, carrying 178 people (including famous Uzbekistan football team «Pachtakor», were flying at the same FL — 8400 m on crossing routes. 20-year-old unexperienced controller was finishing his 6-hour-shift, dealing with extremely high workload, thunderstorm activity, military restrictions, absence of secondary surveillance radar. He and his senior controller actually noticed that 2 aircraft were on collision course and gave appropriate instructions to one of the crews to climb to FL 9000 m, but they didn’t receive clear acknowledge from the pilots and that was major controllers’ mistake. Poor communication stopped the crew from hearing the command, so both of the planes remained at the same level and eventually collided. 24.08.1981 Antonov-24 and Tupolev-16 collision over Zavitinsk. Poor coordination between civil and military controllers of Amur region led to misunderstanding about place and altitude of maneuvers of two strategic bombers Tu-16, crossing the path of civil An-24 on it’s way to Blagoveshchensk airport. One of the bombers collided with An-24 at FL 5400 m, killing 37 people on both aircraft. The sole survivor, 20-year-old passenger Larisa Savitskaya from An-24, was rescued on the third day after the accident. 03.05.1985 Tupolev-134 and Antonov-26 collision over Lvov. An approach controller didn’t have secondary surveillance radar, so he confused blips from two aircraft on his primary surveillance monitor and gave instruction to Tu-134 crew to descend from FL 4200 m to FL 3600 m, not realizing that this would lead to collision with An-26, flying at 3900 m in opposite direction. In last 3 seconds before the collision pilots of both aircraft saw each other , but they didn’t have any chances to avoid this tragedy. Investigators revealed many serious flaws in airspace- and work-organization in Lvov airport. For example, controllers were exhausted because of working 11-hour-shifts for 3 months before the accident. ATC-unit boundaries were extremely inconvenient, and some of controllers didn’t have appropriate qualification to work their job.
Prevention and modern safety barriers
Modern collision prevention combines airspace design, flight-plan processing, surveillance, standard separation, readback monitoring and airborne collision avoidance. Controllers need reliable displays and clear coordination procedures. Pilots must comply with clearances, report deviations and respond correctly to TCAS advisories. Safety nets such as short-term conflict alerts can warn a controller, but they do not replace active monitoring.
Workload and fatigue remain important. A technically correct system can still fail if sectors are overloaded, responsibilities are unclear or a warning is presented too late. Training should include ambiguous readbacks, blocked transmissions and situations where an aircraft does not follow the expected vertical profile.
Key vocabulary
- mid-air collision — collision between aircraft in flight
- loss of separation — reduction below prescribed separation minima
- conflicting traffic — aircraft whose trajectories may become unsafe
- crossing tracks — routes that intersect
- readback — pilot repetition of a clearance or instruction
- hearback error — controller failure to detect an incorrect readback
- short-term conflict alert — ground safety net warning of an imminent conflict
- resolution advisory — TCAS vertical guidance for collision avoidance
- sector workload — amount and complexity of traffic handled by a controller
- coordination failure — incomplete or incorrect transfer of operational information
Discussion questions
- Which safety barriers should prevent two aircraft from occupying the same level?
- How can a blocked transmission create a collision risk?
- Why should investigators examine organisational factors as well as individual actions?
- What should a controller do after receiving a TCAS RA report?
- How can sector capacity be reduced during weather or equipment failure?
- Which details are essential when reporting conflicting traffic?