10.4. What is a Near-Miss?

Exercise 10.4.1 Read and translate the text.

Two or more airliners, small aircraft, helicopters, balloons, or military jets come closer to each other than it is legally allowed, such creating the danger for a collision.

The minimum distance of the aircraft depends on the airspace they are flying in. In the approach or departure sector, the spacing can be reduced to a minimum of approximately four nautical miles (7,4 km).

The vertical spacing almost anywhere in the world is 1000 ft for aircraft on opposite headings. Beginning at 29,000 ft altitude the spacing between the flight levels is doubled.

The spacing en-route is most often expressed in flight minutes since, without radar, this is the only practical way to control the distance.

Aircraft flying according to visual flight rules (VFR) in Germany, are fitted in between the IFR flight levels.

The danger arises when aircraft change flight altitudes without coordination, VFR aircraft can climb or descend through IFR flight levels without talking to a controller beforehand. Since light aircraft are often equipped with only a simple transponder (no altitude, encoding), the TCAS of an airliner can’t pick the radar signal up, such not be able to give the airliner crew a resolution advisory. Only the incidents that almost caused a serious accident or that caused an accident with many fatalities are investigated. Many near-misses either go undetected by the crews or, are not being reported.

Still the possibility for a mid-air collision is small. When the airspace is radar monitored the pilots are often released from the mandatory calls at the reporting points. Otherwise the frequencies would be blocked.

If workload permits, good controllers, and there are many of them in the USA and in Europe, will always give traffic information anyway.

By introducing modern systems, such as autopilot, INS, and satellite navigation, the navigational capabilities of the aircraft in maintaining the desired track, altitude and speed have made tremendous progress over the recent years. This makes aircraft fly much more precise both, laterally and horizontally. This capacity is highly desired for precision landings. Enroute, however, the ultimate precision is unintentionally generating a new risk. If aircraft fly on opposing tracks and altitude, they will almost surely collide.

The lateral distance of aircraft depends much on the country they are flying in and on the phase of flight.

Exercise 10.4.2 Answer the questions.

1. What is a near-miss?

2. What does the minimum distance of the aircraft depend on?

3. What is the only practical way to control the distance en-route?

4. When does the danger arise?

5. Can VFR aircraft climb or descend through IFR flight levels without talking to a controller beforehand?

6. Why can’t the TCAS of an airliner pick up the radar signal of light aircraft?

7. What accident are being investigated?

8. Why have the navigation capabilities of the aircraft in maintaining the desired track, altitude and speed made tremendous progress over the recent years?

9. What makes aircraft fly much more precise?

10. What does the lateral distance of aircraft depend much on?

Exercise 10. 4.3 What do the following abbreviations stand for?