What happened
On 28 September 2020, a Cirrus SR22, registration N918SE, was conducting an IFR cross-country flight from Caen Carpiquet to Besançon-La Vèze. The flight, carrying the pilot and two passengers, initially climbed to FL 150. During the approach to runway 23, the pilot requested an RNP approach to facilitate an easier arrival.
As the aircraft approached the destination, the pilot had to navigate around restricted zones, leading to a complex flight path. The aircraft's descent became unstable; the pilot passed the final descent fix (QM406) approximately 30 seconds late. Radar data indicated the aircraft attempted to intercept the glideslope from both above and below, with large-amplitude manual control inputs. During what appeared to be a missed approach maneuver, the aircraft entered a spin and struck trees. Although the airframe parachute system was activated, the impact occurred at an altitude too low for the parachute to fully deploy. The crash resulted in three fatalities and the destruction of the aircraft.
The investigation
The BEA examined the wreckage, flight path data, and cockpit systems. Investigators found that the engine was providing power at the time of impact and the flight controls remained intact, except for the tail unit where fasteners had melted. The investigation focused on the pilot's recent experience with RNP approaches and the aircraft's equipment, specifically noting that the onboard oxygen supply system was inoperative and the oxygen bottle was empty. The investigators also analyzed the physiological risks of flying at high altitudes without supplemental oxygen and the potential for post-hypoxic impairment during descent.
Findings
Several factors contributed to the accident:
- The approach was destabilized by high workload due to complex horizontal and vertical path constraints.
- There was insufficient monitoring of flight parameters or autopilot guidance modes near the final descent fix.
- Manual control inputs failed to maintain the aircraft on the glide path.
- The pilot had limited recent experience with IFR approaches and specific training for the aircraft's recently installed RNP/LPV avionics.
- Flight in conditions conducive to hypoxia—specifically flying above FL 100 for approximately 90 minutes without supplemental oxygen—may have caused post-hypoxic cognitive impairment or fatigue during the descent phase.
Safety action
- The BEA recommended that EASA update its "Preventing Hypoxia" brochure to include information regarding mild hypoxia and post-hypoxic impairments.
- The BEA recommended that EASA update guidance regarding the use of pulse oximeters, noting that these devices can create a false sense of security and should not be used as a primary method for determining the need for supplemental oxygen.