What happened
On July 18, 2005, an Embraer 145 operating from Zurich to Nuremberg landed on runway 28 under heavy rain and turbulent conditions. During the approach, the aircraft encountered significant turbulence and icing, which triggered an automatic software-driven increase in the stall protection speed (SPS/SPEED) by approximately 5 to 7 knots. This increase remained active throughout the landing phase.
Due to heavy winds, the crew applied a 20-knot speed margin to the reference landing speed (VRef), resulting in a touchdown speed of approximately 130 knots. The aircraft crossed the runway threshold at 150 knots, significantly higher than the planned profile. The aircraft touched down 981 meters after the threshold, much later than intended.
As the aircraft decelerated, the braking effectiveness dropped sharply. After 22 seconds, the deceleration decreased from -0.14g to -0.07g, indicating the onset of aquaplaning. Unable to stop before the end of the runway, the pilot steered the aircraft into taxiway F at high speed. The aircraft rotated approximately 200 degrees around its vertical axis and came to a halt on the grass with both main landing gear assemblies. There were no fatalities, though the aircraft sustained minor damage to the tires.
The investigation
The BFU examined the flight data recorder (FDR) and cockpit voice recorder (CVR), as well as runway braking coefficient measurements taken 30 minutes after the event. The investigation focused on the aircraft's landing performance, the impact of the increased approach speed, and the accuracy of the runway condition information provided by the airport tower. Investigators also analyzed the specific type of hydroplaning, identified as rubber reversion hydroplaning, which occurred due to the heat generated by the tires interacting with the wet surface.
Findings
- The primary cause of the runway overrun was aquaplaning on a rain-soaked runway.
- The aircraft's approach was unstable due to gusty winds, leading to an excessive speed margin and a high threshold crossing height.
- The late touchdown point, caused by the high approach speed, reduced the available braking distance by approximately 600 meters.
- The crew was not sufficiently informed of the actual runway condition by the airport authorities.
- The automated increase in stall protection speed due to previous icing encounters contributed to a longer required landing distance.
- The airport's monitoring of runway friction levels was not frequent enough given the rapidly changing weather conditions.