What aircraft was involved and where did it happen?

The accident on 1999-11-18 involved a Eurocopter AS 350 B2, at nahe Reuth, DE.

What was the probable cause of the accident?

The exact cause of the engine failure remains undetermined, though investigators considered the possibility of snow ingestion as a potential factor. The subsequent crash was unavoidable due to the low altitude over forested terrain at the time of the failure.

Engine failure leads to helicopter crash near Reuth

An Eurocopter AS 350 B2 experienced an engine failure during initial climb, resulting in a forced landing in a wooded area and serious injuries to the pilot.

What happened

On November 18, 1999, an Eurocopter AS 350 B2 was performing forestry operations near Reuth following a two-day period of winter weather and snowfall. After a pre-flight inspection and refueling, the pilot initiated the engine warm-up phase. Shortly after takeoff, a member of the ground crew observed a black-and-white smoke cloud emitting from the engine exhaust. The pilot confirmed an engine failure via radio.

At the time of the failure, the helicopter was flying at an altitude of approximately 25 to 30 meters over a forested area. The pilot unhooked the external load container and attempted an autorotation toward a suitable emergency landing site at the edge of the woods. During the approach, the aircraft struck trees and shrubs before impacting the ground heavily in an open area near the forest edge. The accident resulted in serious injuries to the pilot and the total destruction of the aircraft, as well as damage to the surrounding forest.

The investigation

The BFU investigation focused on the cause of the engine failure and the condition of the fuel. Technical examinations of the aircraft at the site showed no immediate signs of mechanical failure. A specialized examination of the engine was conducted by the turbine manufacturer under the supervision of the French accident investigation authority; this inspection found no technical defects or contaminants within the fuel control unit.

Investigators analyzed fuel samples taken from both the helicopter and the refueling truck. These samples contained significant amounts of solid foreign matter, undissolved water, and microbiological contamination. However, the investigation noted that the bypass valve of the fuel filter had not opened, suggesting the engine was receiving filtered, clean fuel. The presence of contaminants in the samples was likely due to improper sampling techniques and the use of contaminated containers rather than the fuel supply itself.

Findings

The primary cause of the engine failure could not be definitively determined.

Investigators could not rule out the possibility that accumulated snow, which may have remained in the engine cowlings despite the pilot's pre-flight cleaning, was ingested into the engine, potentially causing a flameout.

The impact with trees and the subsequent crash were deemed unavoidable due to the low altitude and the lack of accessible clear landing zones at the moment of the engine failure.