What happened
On 21 August 2010, during the Stockholm Air Show, a serious airspace incident occurred over Gärdet in Stockholm. An ATR 72-212 A, registration SE-MDB, was operating a scheduled flight from Visby to Bromma airport. At the same time, a helicopter, registration SE-JBN, was conducting parachute drops as part of the air show program.
As the ATR 72-212 A approached the Nacka radio beacon, the crew was instructed to enter a holding pattern because another aircraft, a DC-3 with registration SE-CFP, was returning to Bromma with an engine failure. While the ATR 72-212 A was maneuvering in the controlled airspace, seven skydivers who had jumped from the helicopter SE-JBN were descending through the same altitude as the commercial aircraft. At approximately 12:29 local time, the skydivers passed within a horizontal distance of 300 meters from the ATR 72-212 A as the aircraft performed a left turn.
The investigation
The Swedish Accident Investigation Board (SHK) examined the sequence of events, radio communications, and the coordination between Bromma Tower and Stockholm Approach (STO SYD). The investigation reviewed radar recordings from the Swedish CAA and the Armed Forces, as well as the flight and sound recorders. The investigators analyzed the workload of air traffic controllers and the specific instructions given to the aircraft involved during the period of high-intensity operations caused by the engine failure on the DC-3.
Findings
- The incident was caused by deficiencies in planning and coordination between the air traffic control centres.
- While air traffic control was aware of the parachuting operations, there was a lack of direct contact between the air show management and air traffic control.
- Communication between the different control sectors was inconsistent, and the correct radio phraseology was not always utilized.
- There was a significant misunderstanding between Bromma Tower and Stockholm Approach regarding the specific instructions for the ATR 72-212 A and the helicopter SE-JBN, leading to the aircraft being directed into a path that intersected with the descending skydivers.