What happened
On March 30, 2014, at 13:42 local time, a near-collision occurred within the Nuremberg control zone between an AVRO RJ100 operating under instrument flight rules (IFR) and an FK9 ELA ultralight aircraft flying under visual flight rules (VFR). The RJ100 was performing a commercial flight from Zurich, Switzerland, carrying 68 passengers and four crew members, while the FK9 ELA was on a private flight from Herzogenaurach to Donauwörth with two occupants.
Prior to the encounter, air traffic controllers had provided traffic information to both crews. The crew of the RJ100 confirmed they had the ultralight in sight via TCAS. At 13:42:29, the TCAS computer in the RJ100 issued a Resolution Advisory (RA) commanding a climb. However, the pilot of the RJ100 observed the ultralight aircraft appearing to be at a slightly higher altitude. To avoid the aircraft visually, the pilot deactivated the autopilot and descended below the ILS glidepath to fly underneath the FK9 ELA.
As the two aircraft crossed paths, the vertical separation decreased significantly. TCAS data confirmed that the RJ100 was approximately 200 feet below the FK9 ELA at the point of closest approach, with a minimum horizontal distance of about 0.07 nautical miles. The pilot of the ultralight aircraft reported seeing the larger aircraft only at the moment the flight paths intersected.
The investigation
The BFU examined the TCAS computer data from the RJ100, flight progress records, and radio communications between the crews and the Nuremberg tower. The investigation also reviewed the flight profiles of both aircraft and the meteorological conditions, which were reported as CAVOK (ceiling and visibility OK) at the time of the event.