What happened
On 21 July 2016, an AVRO 146-RJ100, registration HB-IYT, operated by Swiss Global Air Lines, was performing a scheduled commercial flight from Zurich to Luxembourg. The flight crew initially prepared for landing based on weather forecasts predicting only light, transient showers. However, as the aircraft approached Luxembourg, intense thunderstorm activity developed rapidly.
After an initial approach to runway 24 was aborted due to heavy rain and hail, the crew entered a holding pattern. Following a suggestion from air traffic control, the crew attempted a second approach to runway 06. During the final stages of this approach, the pilot opted to fly manually due to significant turbulence and variable winds. As the aircraft descended, heavy precipitation caused visibility to drop sharply. At approximately 50 feet above the runway, the crew could no longer maintain visual references. The aircraft subsequently made a hard landing with a vertical acceleration of 2.66 g. There were no injuries to the crew or the 66 passengers, and the aircraft sustained no damage.
The investigation
The Swiss Transportation Safety Investigation Board (STSB) conducted the inquiry, which was delegated to them following discussions with Luxembourg authorities. The investigation utilized flight data monitoring, air traffic control recordings, and meteorological analysis. Investigators examined the rapid succession of ATIS updates, which showed a significant intensification of the storm, and analyzed the development of a "daughter cell" over the runway threshold. The investigation also reviewed the flight crew's training records and the fuel management decisions made during the holding pattern.
Findings
- The flight crew's decision to land was influenced by limited fuel reserves, as a second go-around would have necessitated an immediate diversion to Brussels.
- A spontaneous wet microburst or similar intense precipitation cell developed over the runway threshold, causing a sudden loss of visibility and wind shear.
- The flight crew was heavily focused on completing the landing due to the high-risk environment and the difficulty of performing a go-around through an active storm cell.
- While the initial weather forecasts were relatively optimistic, the inherent uncertainty of thunderstorm forecasting contributed to the crew's unexpected encounter with severe weather.