On 17 January 2014, two light aircraft breached the airborne separation minima during their final approaches to Groningen Airport Eelde (GAE). LVNL has reported this incident to the Dutch Safety Board and is conducting its own investigation.
Loss of separation
The horizontal or vertical distance between aircraft in flight is referred to as their “separation”. Separation minima have been established to maintain air traffic safety, whilst at the same time making optimum use of airspace. Air traffic control is responsible for maintaining these minimum distances between aircraft in its control zone. When two aircraft come closer to one another than the minima allow, the situation is known as a “loss of separation”.
The criteria for separation minima have been designed in such a way that they allow enough time to correct the situation before it presents a serious danger. An air traffic controller faced with a loss of separation must undertake a number of steps in a very short time.
- Detect the loss of separation;
- Identify an effective solution;
- Communicate that solution to the pilot(s) concerned, in the form of instructions regarding their altitude, bearing and speed;
- Ensure that the pilot(s) follow these instructions in order that safe separation is restored as quickly as possible.
LVNL’s primary safety task is to maintain the separation of aircraft from one another, and also from vehicles and other obstacles when on the ground. Air traffic controllers internally report any incidents falling within our area of responsibility, with the aim of learning lessons from them and so reducing the chance that similar occurrences will take place again in the future. All reported incidents are investigated by LVNL, as part of our ongoing commitment to improving safety.
Summary investigation results
LVNL has conducted a summary investigation into the loss of separation between two aircraft at Groningen Airport Eelde (GAE). The results of this are now known. Below is a brief summary of the incident.
On 17 January 2014, a Diamond 42 (DA42) was approaching GAE at an authorised height of 3000 feet. Behind this aircraft was a Cessna 172, which was cleared by ATC to begin its final approach at a height of 2000 feet. At this point the Cessna’s airspeed was lower than that of the DA42 in front of it.
However, the pilot of the DA42 was under the mistaken impression that he had also received clearance to make his final approach. On his own initiative, he therefore began to reduce altitude in preparation for landing. As a result, a loss of separation occurred between the two aircraft. At their closest, they were 1.8 nautical miles from one another. Both flights were monitored visually from the control tower at the airport, both were able to continue without further incident and both made a normal landing.
Classification: significant incident