Incident Overview
On 15 February 2004, at approximately 14:52 UTC, an air proximity event occurred 6 nautical miles southwest of Grenchen, near the waypoint LARDO, within the Bern Terminal Control Area (TMA) Class D airspace. The aircraft involved were a Pilatus Porter PC6T (registration HB-FLK) operated by Para-Club Grenchen and a De Havilland DHC-8-314 (registration D-BHOQ) operating as DLH8AY on behalf of Lufthansa. The DHC-8 was on a scheduled instrument flight from Munich to Bern, while the Pilatus Porter was conducting a visual flight for parachute dropping.
Flight Details
DLH8AY was initially cleared to flight level 100 (FL100) via the waypoints BELAR, LARDO, and BIRKI for an instrument approach to runway 14 at Bern. At 14:49:21, Bern TWR/APP cleared the aircraft to descend to FL80. Shortly after, at 14:49:43, the pilot of HB-FLK contacted Bern TWR/APP to request a climb to FL140 for parachute operations. At the time, DLH8AY was approximately 11 NM from HB-FLK, passing through FL110 descending to FL80.
ATC Communications
At 14:50:30, Bern TWR/APP authorized HB-FLK to proceed towards the designated climb sector (Steigsektor) and climb to FL100. However, the pilot reported clouds and requested to first fly towards Schnottwil. In response, at 14:50:42, ATC limited the cleared altitude to 5000 ft. At 14:51:10, DLH8AY was cleared to descend to 6000 ft.
At 14:52:17, the pilot of HB-FLK informed ATC that he was turning towards the climb sector and ascending to FL100. Over the next 30 seconds, Bern TWR/APP issued three instructions to HB-FLK to maintain 5000 ft, stating that there was IFR traffic above. The pilot replied that he could not maintain 5000 ft due to clouds, and proposed 5500 ft, which was denied. At 14:52:42, the pilot reiterated that he could not stay at 5000 ft due to cloud conditions; at that time, HB-FLK was at 5600 ft.
At 14:52:50, Bern TWR/APP issued an essential traffic information to DLH8AY, advising of traffic at their one o'clock position, two miles, 5600 ft in climb, and instructed the crew to initiate a left turn to BIRKI. The crew of DLH8AY reported visual contact with the Pilatus Porter and subsequently maintained sight. According to their statement, they kept the Porter in sight throughout.
Separation
Radar recordings showed that at 14:53:09, the two aircraft passed with a horizontal separation of 1.8 nautical miles and a vertical separation of 400 feet. At 14:53:21, the separation was 1.9 NM horizontally and 100 feet vertically. The pilot of HB-FLK later stated that he saw the DHC-8 pass behind him.
Equipment and Weather
Both aircraft had their transponders with altitude reporting (Mode C) activated and were visible on the Bern TWR/APP bright display. The DLH8AY crew reported that their TCAS issued a Traffic Advisory (TA) but no Resolution Advisory (RA). The weather at the time was described as scattered to broken clouds, with cloud tops around 5500 feet. Meteorological reports from Grenchen and Bern indicated scattered clouds at 3400 and 2000 feet, respectively, with broken layers above.
Additional Findings
The Bern TWR/APP position was staffed by a trainee under the supervision of a licensed air traffic controller. Both controllers were appropriately licensed. They had been on duty since 08:10 and had been at the combined TWR/APP position for approximately three hours at the time of the incident. The controllers assessed the situation as dangerous. The jump operation had not been prenotified to Bern TWR/APP because the decision to fly was made spontaneously after the weather improved during the afternoon.