On July 16, 2024, an Airbus Helicopters AS 350 B2 was involved in an aviation accident near nahe Wiesenbach, DE. This summary draws on records from the German Federal Bureau of Aircraft Accident Investigation (BFU).
On 16 July 2024, an Airbus Helicopters AS 350 B2 made an emergency landing near Wiesenbach after a sudden power loss during external load operations. The pilot was uninjured, and the helicopter sustained minor damage.
Incident Overview and Flight Details On 16 July 2024, a single-engine Airbus Helicopters AS 350 B2 helicopter was conducting external load operations, specifically forest liming, near Wiesenbach. The aircraft, manufactured in 2002 with serial number 9054, was operated by a German aviation company. The pilot, a 28-year-old commercial helicopter pilot with approximately 2,400 total flight hours, was the flight operations manager for the company. The day began with a pre-flight inspection, during which approximately 10 ml of water was found in the main tank during the first drain, but no water was detected in the second drain. The helicopter was then refueled with 60 liters of Jet A1 from a mobile fuel unit. The first flight of the day, starting at 08:20 local time, involved 35 circuits over 50 minutes and concluded with approximately 60 liters of fuel remaining, with no engine issues reported. For the subsequent flight, the helicopter was refueled with 160 liters of Jet A1, bringing the total fuel load to approximately 220 liters at the 09:55 start. The first 40 minutes and 26 circuits were uneventful. However, when picking up a new load of approximately 750 kg of lime, the pilot noticed a drop in main rotor RPM without triggering the low-rotor-RPM warning. The pilot continued with lighter loads for about 10 minutes and 5 circuits before experiencing a sudden yaw and suspected power loss during another load pickup. The pilot performed a controlled landing on a forest road and aborted the operation. ## Investigation and Findings Post-landing inspection revealed a significant amount of contaminated, brown-colored fuel in the tank. Multiple drain operations were performed until clear fuel was obtained. After consulting with the Continuing Airworthiness Management Organisation (CAMO) and the maintenance manager, the engine was restarted, and the helicopter was moved to a level area. Further contaminated fuel was drained, leading to the decision to completely empty the tank. The helicopter was refueled with 190 liters of fresh fuel from a different vehicle. After a pre-flight check, the engine was started at 18:06, and a ground run and hover test were conducted. All parameters were normal, and the pilot resumed the liming operation. At 18:22, while picking up a load of approximately 600 kg of lime, the helicopter yawed, main rotor RPM decreased, and the low-rotor-RPM warning sounded. The pilot initiated an autorotation and landed in a clearing with low vegetation. The helicopter touched down in a nose-down attitude on soft forest ground and came to rest upright with minor damage. The pilot exited the aircraft uninjured. ## Aircraft and Environmental Conditions The AS 350 B2 is a light multi-purpose helicopter with a maximum takeoff weight of 2,250 kg (2,500 kg with external load). It is powered by a Safran Helicopter Engines Arriel 1D1 engine and features a three-blade main rotor and a tail rotor. The fuel system includes an airframe fuel filter and a Fuel Control Unit (FCU) fuel filter, both of which showed brown contamination during the investigation. Meteorological conditions at the time of the incident included visibility of more than 10 km, a light wind from 300° at 5-10 knots, a temperature of 20°C, and a QNH of 1,014 hPa. The helicopter was not equipped with a Flight Data Recorder (FDR) or Cockpit Voice Recorder (CVR), as these were not required. ## Damage and Subsequent Analysis The helicopter sustained minor damage, including broken skid tips, a dented lower fuselage fairing, and a deformed rib below the cockpit. The external load and lime bucket remained attached to the helicopter. The aircraft was recovered and transported to Egelsbach for further investigation on 26 July 2024. Engine inspection revealed no mechanical issues, with the N1 and N2 drive trains turning freely and no metal chips detected. The airframe and FCU fuel filters showed significant brown contamination, and samples were sent to the Wehrwissenschaftliches Institut für Werk- und Betriebsstoffe (WIWeB) for chemical analysis on 30 July 2024.