Incident Overview
On February 4, 2014, a Hélicoptères Guimbal Cabri G2 helicopter was involved in an accident near Langenfeld, Germany. The aircraft, which sustained heavy damage, was operating for a pipeline inspection when it crashed into a meadow. Both occupants, professional pilots, exited the wreckage unharmed.
Operational Context and Sequence of Events
The flight originated from Bonn-Hangelar (EDKB) with a destination of Stadtlohn-Vreden (EDLS). During the mission, the crew observed construction equipment near the pipeline route and landed on a grassy field to assess the situation. Upon attempting to take off against the wind, the helicopter began rotating uncontrollably to the left around its vertical axis.
The pilot reported that despite applying full right pedal input, the rotation continued to accelerate. Attempts to regain control using collective pitch adjustments failed. The aircraft eventually touched down on its left skid and rolled onto its left side. No fire occurred, and approximately 54 liters of fuel remained on board.
Aircraft and Environmental Factors
The Cabri G2 is a two-seat helicopter featuring a Fenestron tail rotor system for yaw control. The specific airframe involved was manufactured in 2013 with serial number 1045. At the time of the accident, it had accumulated approximately 624 flight hours. Meteorological conditions at nearby Düsseldorf Airport indicated winds from 160 degrees at 9 knots and clear visibility.
Investigation Findings
The German Federal Aviation Office (BFU) concluded that the incident was related to the handling characteristics of the Fenestron system compared to conventional tail rotors. Following three similar accidents involving uncontrolled yaw, the BFU conducted comparative flight tests in March 2014 using a Robinson R22 and a Cabri G2. These tests confirmed that the Fenestron requires significantly greater pedal travel for equivalent torque compensation, a characteristic highlighted in manufacturer Service Letter 12-001.