History of Flight
On 21 December 2023, OY-JZN, a Boeing 737-800, operated a charter flight from Hurghada (HEGN) to Billund (EKBI) with Gothenburg (ESGG) as the planned destination alternate. The aircraft had been delayed 28 hours due to a technical malfunction of a leading edge flap proximity sensor, which was corrected by an operator aircraft technician at HEGN before departure.
Fuel Planning
The flight crew updated the Operational Flight Plan (OFP) with assistance from the operator's Operational Control Centre (OCC). The available OFP indicated a minimum required fuel of 16,814 kg. OCC verbally communicated a revised minimum of 17,400 kg based on the latest winds aloft forecast, but the crew could not update the OFP on their Electronic Flight Bags (EFB). They added 1,186 kg of extra fuel due to the outdated winds forecast, a forecasted storm in Denmark, and the previous malfunction. The aircraft departed HEGN at 15:45 hrs with 17,890 kg of take-off fuel.
Approach and Missed Approach
At 18:20 hrs, approximately halfway, the crew noticed the estimated landing fuel had decreased from 4,000 kg to 3,200 kg. They changed the destination alternate from ESGG to Copenhagen, Kastrup (EKCH), due to its proximity and more favourable wind conditions. At 21:09 hrs, with 3,278 kg of fuel remaining, the aircraft was established on the Instrument Landing System (ILS) for runway 27 at EKBI. Billund Approach/Tower cleared the aircraft to land and advised that in case of a missed approach, they could climb to any desired altitude. Wind conditions were 310°/36 knots, gusting 50 knots. During the approach, the aircraft remained stabilised at 1,000 ft and 500 ft above ground level, but at a radio altitude of 300 ft, the Enhanced Ground Proximity Warning System (EGPWS) issued an aural windshear warning. The flight crew initiated a go-around and performed a missed approach.
Flap Overspeed and System Failure
During initial climb-out, the flight crew selected Take-Off and Go-Around (TOGA) thrust, retracted the landing gear, and moved the flap lever from 30° to 15°. The Flap Slat Electronic Unit (FSEU) commanded an automatic flap retraction while the crew moved the handle. A flap solenoid valve failed to reset, and the FSEU removed power to the flap drive system when the flaps reached position 13°. The aircraft remained in a non-normal configuration with flaps at 13°.
Diversion and Fuel Emergency
Due to the weather conditions, the flight crew decided to divert to the destination alternate, EKCH. The increased fuel consumption from the flap 13° configuration caused the estimated landing fuel to fall below the required minimum final reserve of 1,118 kg (equivalent to 30 minutes of flight). At 3,090 kg remaining fuel, the crew declared a fuel emergency, resulting in Air Traffic Control (ATC) priority and direct routing.
Landing
The aircraft landed at EKCH with 119 kg (three minutes) less than the required minimum final reserve fuel. The serious incident occurred in darkness and under Visual Meteorological Conditions (VMC).