What happened
On December 17, 1997, a Lufthansa CityLine CL-600 Regional Jet (DLH-5204) operating a scheduled service from Munich to Helsinki discovered during the flight that its fuel load was insufficient due to a calculation error. The error, which involved a discrepancy of approximately 1,000 kg in the flight plan, was identified after the aircraft had already departed.
To manage the shortage, the crew recalculated their requirements, determining that they could reach Helsinki if they were permitted to use runway 04 instead of the assigned runway 22. Using runway 04 would allow for a radar-guided approach, avoiding the longer procedures required for runway 22 and saving critical fuel. The crew also adjusted their flight profile to more economical speeds and optimized their descent.
As the aircraft approached Helsinki, the captain notified Air Traffic Control (ATC) that the fuel levels were approximately 100 kg below the required minimum for the destination. In response, the Helsinki-Vantaa approach controller denied the request for runway 04 due to traffic conditions but offered runway 15 as an alternative. The crew requested priority handling to ensure reserves were not depleted during the approach. Consequently, the tower controller alerted emergency services, and rescue units were placed on standby.
The investigation
The investigation focused on the flight planning process, the management of the fuel shortage, and the communication between the flight crew and ATC. Investigators examined the accuracy of the fuel calculations, the crew's decision-making regarding fuel-saving measures, and the clarity of radio communications regarding fuel status. The investigation also looked into the reporting procedures used by the controller to document the incident and the subsequent misunderstanding between the crew and the ATC supervisor regarding the actual remaining fuel volume.