What happened
On the morning of September 15, 2012, a Cessna R182, registered as HB-CLU, was conducting an instrument flight rules (IFR) training flight departing from Bern-Belp Regional Airport. After climbing to 6,000 feet, the crew received instructions to turn left to a heading of 310 degrees. During this maneuver, the aircraft transitioned between cloud cover and clear air. As the crew executed the turn, they suddenly spotted a hot air balloon, a Fire Balloons G 34/24 with registration HB-QIK, at the same altitude in their 2 to 3 o'clock position. The crew believed that without the recent course change, a collision would have occurred.
Simultaneously, the pilot of the hot air balloon was ascending through a cloud layer at approximately 1,900 meters. The balloon had entered the Bern-Belp control zone without the pilot realizing it. Due to the noise from the balloon's burners, the pilot did not hear the approaching aircraft until visual contact was nearly made.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the flight paths, meteorological conditions, and communication logs. The investigation established that the balloon pilot was not in radio contact with Bern-Belp air traffic control and was not carrying a transponder. Consequently, air traffic control radar could only detect the balloon briefly and without altitude information. The investigation also reviewed the procedures for flying through fog and clouds (nebeldurchstossverfahren) used by balloon pilots in Switzerland.
Findings
- The balloon pilot entered the controlled airspace of Bern-Belp without notifying air traffic services.
- The lack of a transponder on the hot air balloon prevented air traffic controllers from accurately tracking the aircraft's position and altitude.
- There is a deficiency in training regarding the specific procedures for balloon pilots when ascending through cloud or fog layers.
- The pilot of the balloon did not hear the aircraft due to the operational noise of the balloon's burners.