History
On Sunday, 12 September 1999, at 0728 UTC, KLM flight 1933, a Boeing 737-300 operating from Amsterdam to Geneva, was under radar guidance of Geneva Arrival control. The aircraft was descending to 7000 ft. The pilot indicated readiness to turn towards the final approach for runway 05. The controller observed unknown traffic near the Chambéry VOR with transponder code A7010 at 6500 ft, on a reciprocal route. The controller kept KLM1933 at 7000 ft to maintain separation and provided traffic information. KLM1933 was turned to a heading of 190 degrees for a base turn, then to 090 degrees for ILS interception, still at 7000 ft. The pilot did not establish visual contact despite VMC conditions. After receiving a TCAS resolution advisory, the pilot informed the controller of a climb to avoid the traffic. Minimum separation was 1.3 NM horizontally and 600 ft vertically. The controller then advised that the traffic was behind KLM1933 and re-authorized descent for a visual approach. KLM1933 completed a normal approach and landing. The pilot submitted an ATIR report by radio on 119.9 MHz.
Findings
- The aircraft was under radar control on frequency 131.320 MHz.
- KLM1933 was on an intermediate approach descending to flight level 100, then re-authorized to 7000 ft.
- The unknown aircraft displayed transponder code A7010 and penetrated the terminal area in airspace C at 6500 ft without radio contact.
- The controller provided traffic information to KLM1933: "Unknown aircraft, traffic VFR at 11 o'clock, 6 NM, opposite, probably at 6500 ft."
- The controller turned KLM1933 to heading 140 degrees for base turn.
- KLM1933 advised seeking visual contact.
- The controller did not authorize descent for KLM1933.
- Radar trace showed KLM1933 would cross the unknown aircraft's route.
- The controller held another incoming aircraft (Speedbird 730) at flight level 080 due to the unknown traffic.
- The controller turned KLM1933 to heading 090 degrees for ILS interception, with traffic information: "position 1 o'clock, 2 NM, opposite, 6500 ft."
- After a call from incoming traffic, confusion occurred on the frequency.
- KLM1933 acknowledged the heading and reported climbing to avoid traffic.
- Minimum separation was 1.3 NM horizontally and 600 ft vertically.
- KLM1933 stated no visual contact but followed TCAS resolution advisory.
- The controller advised when the unknown traffic was behind.
- KLM1933 was then authorized for visual approach.
- Meteorological conditions were VMC with visibility exceeding 10 km.
- The pilot submitted an ATIR report.
Analysis
The encounter occurred in class C airspace in the Geneva terminal control area. The unknown aircraft was visible to secondary radar and was indicated to the pilot. According to radar trace, it penetrated the Chambéry TMA descending from 7700 ft to 6500 ft, stabilized, then entered the Geneva TMA. It was in E airspace in Chambéry TMA and later in C airspace crossing Geneva. It did not make radio contact with Geneva TMA. After leaving, it re-entered E airspace. Over 36 NM, it encountered three airspace classes. The controller maintained KLM1933 at 7000 ft above the unknown aircraft's 6500 ft. Despite two precise traffic advisories, the pilot could not visually acquire the traffic and followed TCAS advisory. The pilot reported 500 ft vertical spacing per TCAS; radar showed 1.3 NM horizontally and 600 ft vertically. Swisscontrol noted numerous incidents with unknown aircraft in the area and provided radar trace to French authorities for identification.
Cause
The incident is due to an unauthorised incursion of an aircraft into the Geneva terminal area; airspace class C.