What happened
On August 10, 2024, at approximately 20:15 UTC, a LEONARDO A109S helicopter, registration EC-NRI, operating as a HEMS (Helicopter Emergency Medical Service) flight, was involved in an accident at a sports field in Cabra, Córdoba. The aircraft, operated by AVINCIS, had landed to collect a patient suffering from a myocardial infarction.
After the patient was loaded and the stretcher secured, the pilot began the engine start sequence. During this time, a medical professional attempted to administer oxygen to the patient. Upon opening the valve of an oxygen cylinder, a sound similar to a deflagration occurred, immediately triggering a fire in the left side of the cabin.
The crew and medical personnel attempted an emergency evacuation. The HEMS crew member attempted to release the stretcher from its mountings despite the flames, eventually managing to free the patient's torso, though the patient's legs remained momentarily trapped. The patient, the crew member, and a medical professional all sustained severe injuries (burns). The pilot and the doctor were uninjured. The aircraft was destroyed by the fire, and the incident caused damage to the artificial turf of the sports field.
The investigation
Investigators utilized crew testimony and surveillance footage from the sports complex to pinpoint the fire's origin. The fire started inside the cabin, specifically in the area between the left front seatback and the front of the stretcher, where the oxygen therapy system was located.
The medical equipment used was an Aerolite HEMS kit, which utilized a 5-liter Takeo B5 oxygen cylinder manufactured by Air Liquide Medical Systems (ALMS). The investigation focused on the remains of the oxygen cylinders, which were sent to a laboratory in France for examination.
Findings
Laboratory analysis of the cylinder remains concluded that the fire originated within the valve of the Takeo B5 cylinder, specifically at the distribution valve, before spreading to the pressure regulator and the 4-bar pressure outlet.
Investigators determined that the most probable ignition mechanism was heating caused by oxygen flow friction, although the possibility of ignition via particle impact has not been ruled out. While the origin and ignition mechanism were identified, the total destruction of the aircraft prevented investigators from determining what caused the high oxygen flow rate that led to the event.