What aircraft was involved and where did it happen?

The accident on 2013-06-21 involved a aircraft, registration 9H-GTY, at 1 NM nordöstlich des Regionalflugplatzes Bern-Belp LSZB, BE, CH.

What was the probable cause of the accident?

The incident was caused by the business jet's excessive approach speed, which invalidated the controller's traffic planning, compounded by poor situational awareness and inadequate monitoring by the flight crew.

High-speed approach leads to near-collision near Bern-Belp

An excessive approach speed by a Beechcraft 350i caused a dangerous airprox with a motor glider near Bern-Belp, triggering TCAS resolution advisories.

What happened

On June 21, 2013, a high-risk airprox occurred approximately one nautical mile northeast of Bern-Belp Regional Airport. A Beechcraft B350i, registration 9H-GTY, operating as flight MLT 251, was performing an instrument approach to runway 14, followed by a circling approach to runway 32. Simultaneously, a Diamond HK 36 TTC, registration HB-2377, was departing from the glider strip for an overhead crossing maneuver.

As the B350i transitioned to its downwind leg, the crew received traffic information regarding the glider. However, the aircraft was traveling at a significantly high ground speed. The onboard TCAS system issued a Traffic Advisory (TA) followed by a Resolution Advisory (RA) instructing the crew to "monitor vertical speed." The two aircraft crossed paths with a horizontal separation of only about 400 meters and a vertical separation of approximately 410 feet. The crew of the B350i did not visually identify the glider, seeing it only as a symbol on their navigation display, while the crew of the HB-2377 did not see the business jet at all.

The investigation

The SUST investigation examined the flight paths, technical data from the flight recorders, and air traffic control communications. Investigators reviewed the cockpit voice recordings and TCAS event logs from 9H-GTY, as well as the Mode-S downlink data. The investigation also analyzed the workload of the Bern aerodrome control tower, noting that the period between 12:50 and 13:15 UTC was characterized by very high traffic density, high complexity, and frequent radio frequency congestion.

Findings

The primary cause of the incident was the excessive approach speed of the B350i, which disrupted the air traffic controller's planned traffic sequencing.
Contributing factors included inadequate airspace monitoring by the crew of the B350i and an inappropriate flight tactic.
High traffic frequency and complexity at the aerodrome acted as contributing environmental factors.
There were no technical malfunctions or health issues identified in the crews or the air traffic controller.

Safety action

Following the incident, the air navigation service provider, Skyguide, implemented several measures to reduce complexity in the Bern airspace. These included expanding the 'Prior Permission Required' (PPR) requirements for external aircraft, more restrictive handling of the 'LIMA BRAVO' sector, reinstating restrictions for IFR training approaches, and closing the Bern CTR9 for transit flights below 5,000 feet AMSL.