Engine failure and stall lead to fatal ultralight accident in France

Casualties unknown • Guiscriff Scaer, FR

A RANS Coyote II S-6ES ultralight crashed during a training flight near Guiscriff, France, resulting in the deaths of both the instructor and student.

What happened

On July 15, 2016, an instructor and a student were performing circuit training at the Guiscriff-Scaer aerodrome. During the third takeoff of the session, at an altitude of approximately 100 meters, the engine of the RANS Coyote II S-6ES, registration 35-FF, suddenly stopped. Witnesses observed the aircraft banking to the left in an attempt to perform a 180-degree turn back toward the runway. Following this maneuver, the aircraft experienced an asymmetric stall to the right and entered a steep dive, striking the ground approximately 400 meters from the threshold of runway 02. The impact resulted in two fatalities and the total destruction of the aircraft.

The investigation

The BEA examined the wreckage and the propulsion system to determine the cause of the engine failure. Investigators found that the propeller had been stopped (stalled) at the moment of impact. While the engine itself showed no internal mechanical damage, the investigation focused on the ignition and fuel systems.

Regarding the ignition system, investigators discovered damage to one of the two electronic control units, which prevented power from reaching the upper spark plugs of cylinders 3 and 4. Notably, this damaged area had been covered with adhesive, suggesting the fault had been identified prior to the flight but not properly repaired.

In the fuel system, investigators found glass fiber contamination within the left carburetor bowl and the idle jet of the right carburetor. This contamination was also present in the fuel lines, one of which was completely blocked. The investigation traced these fibers back to the degradation of the aircraft's grey-colored fuel tanks, an older generation of tanks known to degrade over time.

Findings

  • The engine failure was caused by a combination of fuel system contamination from degrading fuel tanks and a malfunction in the ignition system.
  • The asymmetric stall and subsequent crash were likely caused by insufficient airspeed monitoring while attempting to execute a turnaround at a low altitude.
  • The decision to attempt a 180-degree turn toward the runway following the engine failure likely contributed to the loss of control.

Probable cause

The engine failure was driven by glass fiber debris from degrading fuel tanks clogging the fuel system, compounded by a previously identified but inadequately repaired ignition fault. The subsequent fatal stall was caused by insufficient airspeed management during an emergency turn at low altitude.

Frequently asked questions

What happened in the 2016-07-15 RANS Coyote II S-6ES accident near Guiscriff Scaer, FR?

A RANS Coyote II S-6ES ultralight crashed during a training flight near Guiscriff, France, resulting in the deaths of both the instructor and student.

What aircraft was involved and where did it happen?

The accident on 2016-07-15 involved a RANS Coyote II S-6ES, registration 35-FF, at Guiscriff Scaer, FR.

What was the probable cause of the accident?

The engine failure was driven by glass fiber debris from degrading fuel tanks clogging the fuel system, compounded by a previously identified but inadequately repaired ignition fault. The subsequent fatal stall was caused by insufficient airspeed management during an emergency turn at low altitude.

Loading the flight search…