4 September 2016 - Loss of separation due to airspace infringement Amsterdam Airport Schiphol

Notification

On Sunday 4 September 2016 a sport aircraft entered Amsterdam Airport Schiphol airspace without permission. It flew in the vicinity of a flight controlled by air traffic control, approaching Schiphol for landing. The two aircraft came closer to each other than is allowed by the separation minima. LVNL is investigating the occurrence and has reported the occurrence to the Dutch Safety Board.

What is an airspace infringement?

Internationally, an airspace infringement is defined as: “A flight into notified airspace without previously requesting and obtaining approval from the controlling authority of that airspace in accordance with international and national regulations.”

Occurrence investigation

LVNL’s primary safety task is to maintain the separation of aircraft in the air, and between vehicles and other obstacles when on the ground. Air traffic controllers internally report any safety related occurrence, with the objective to learn lessons from those occurrences,  thereby reducing the chance that similar occurrences will take place again in the future. All reported occurrences are investigated by LVNL, as part of LVNL’s ongoing commitment to improve safety.

Situation description

An aircraft of the type Boeing 737-800 was approaching from the east for a landing on the Buitenveldertbaan and received instructions from Schiphol approach control. At the same time, a light aircraft of the type Cessna 172 was flying on a south westerly course along the coast of the IJmeer.

The Cessna flew into the control zone of Schiphol approach control.

Approach control had the Boeing descend to an altitude of 2,000 feet - approximately 600 metres - for an instrument approach. The Cessna was flying at 1,500 feet - approximately 457 metres - with an unverified altitude read-out. Approach control informed the pilot of the Boeing about the Cessna by providing traffic information.

The Cessna ascended unexpectedly, and without permission from air traffic control, into Amsterdam Airport Schiphol’s approach zone up to an altitude of approximately 1,800 feet - 548 metres. Meanwhile, the pilot of the Boeing reported visual contact with the Cessna to the approach controller. The following flight approaching the Buitenveldertbaan received course instructions from approach control to keep clear of the Cessna.

Investigation result

Both flights were able to continue their flight without problem. The pilots of the Boeing indicated in the trip report submitted after landing that there had been a Traffic Alert TCAS warning.

A following flight that was approaching the Buitenveldert runway received a course correction from the approach  Controller to maintain separation from the Cessna. This flight was also able to continue its approach without problems.

Minimum separation

The minimum separation between the Boeing and Cessna 172, shown on the radar screen, was 1.1 nautical miles - circa 2,000 metres - horizontal and 200 feet - circa 60 metres - vertical.

Air traffic - often recreational - that flies below the area controlled by Schiphol Approach is allowed to fly in the area up to a maximum altitude of 1,500 feet - circa 450 metres. This traffic is not allowed to enter the area controlled by Schiphol Approach. The Schiphol approach controller ensures that the air traffic under his/her control does not descend to below a minimum altitude of 2,000 feet - circa 600 metres. This ensures that there is always a minimum vertical buffer of 500 feet - circa 150 metres - between air traffic approaching Schiphol airport and recreational air traffic.

Conclusion and follow up

The incident was the result of - according to the data presented to the air traffic controller - the Cessna entering the area controlled by Schiphol Approach without permission.

The pilot of the Cessna has indicated that his data shows that the Cessna was flying below the approach area. LVNL cannot determine in hindsight whether the Cessna actually flew in the area or whether the altitude sent by the transponder of the Cessna was incorrect.

Air traffic controllers depend on the data presented on the radar. TCAS, the warning system designed to prevent passenger aircraft collisions, also assumes the altitude sent by the transponder. Therefore, properly operating transponders are of extreme importance for the safety in the busy airspace around Schiphol.

Classification: major incident