What happened
On July 17, 2004, a KLM Cityhopper scheduled flight from Zurich to Amsterdam Airport Schiphol encountered extreme weather during its approach to runway 27. While at approximately 1,500 feet, the Fokker F.28 Mk. 0070, registered PH-KZI, encountered severe windshear characterized by wind gusts reaching 50 knots. The turbulence caused a violent reaction in the aircraft, resulting in the landing gear extension speed being exceeded by roughly 20 knots.
Following the encounter, the crew aborted the approach and initiated a northward turn to avoid the weather. Due to the deteriorating conditions at both the destination and the primary alternate airports in Rotterdam and Groningen, the crew elected to divert to Bremen. During the transit to Germany, the crew declared a low fuel emergency to air traffic control. The aircraft landed safely at Bremen with 750 kg of fuel remaining.
The investigation
The investigation, conducted by the predecessor of the Dutch Safety Board at the request of the German authorities, examined the fuel planning and weather considerations for the flight. The inquiry reviewed the standard fuel requirements, including taxi, trip, contingency, alternate, and final reserve fuel.
The investigation analyzed the weather forecasts used during flight planning. While the forecasts for Amsterdam and the planned alternate in Rotterdam indicated conditions above minimums, they did show variable winds and gusts up to 36 knots, signaling heavy thunderstorm activity. The investigation also looked at the crew's decision-making regarding the declaration of a fuel emergency and the selection of a diversion airport under heavy weather conditions.