US HEMS EC135P1 Dual Engine Failure: 7 July 2018
On the evening of 7 July 2018, at about 21:23 Local Time, Airbus Helicopters EC135P1 N312SA, powered by two Pratt & Whitney Canada (PWC) PW206B3 turboshafts, impacted the ground hard after an autorotation following a dual engine failure over Chicago, Illinois. The helicopter operated by Pentastar Aviation Charter as a Part 135 helicopter air ambulance (HAA/HEMS) flight for Superior Ambulance.
The pilot and paramedic sustained minor injuries, the flight nurse sustained serious injuries, and the patient was not injured during the accident.
The helicopter sustained substantial damage to the fuselage, tailboom, and main rotor blades.
The Accident Flight
The NTSB report that:
…satellite tracking and air traffic control information revealed the helicopter was traveling northwest from the St. Mary Medical Center on a direct route to Advocate Christ Medical Center about 1,000 ft above ground level. About 5 miles southeast of Advocate Christ Medical Center, the helicopter turned to the right after the pilot requested to return to the Gary, Indiana, airport. About 50 seconds later, the pilot declared a “mayday” and stated the helicopter was going down into a field. The helicopter came to rest upright in a grass area between the Interstate 94 and Interstate 57 interchange.
Surveillance video from a Chicago Transit Authority rail platform located adjacent to the accident site depicted the helicopter during the final phase of the autorotation and impact with terrain. The video showed a fire near the number 2 (right) engine during the autorotation. A[n] explosion was observed after the impact with terrain.
Examination of the Wreckage
Investigators say that:
….the initial impact was consistent with the fenestron skid cap contacting the terrain first, followed by the landing gear skids and fuselage. The left landing gear skid was separated and came to rest near the ground scar consistent with the fuselage. The fuselage was crushed upward, and the fenestron assembly was separated at the tailboom attachment location.
The pilot seat, paramedic seat, and flight nurse seat were found fully attenuated.
Thermal damage was noted on the right engine and main transmission cowling.
Both engines power turbine wheel blades were missing the outer halves of the blades. Multiple impact dents, consistent with the fractured turbine blades, were noted inside the exhaust stubs. The No. 1 engine had a 1/2″ by 1/2″ hole in the exhaust stub at the 2 o’clock position forward of the aft firewall, and the No. 2 engine had a 2″ by 1″ hole in the exhaust stub at the 11 o’clock position forward of the aft firewall.
Next Steps in the Investigation
The helicopter was equipped with Outerlink IRIS. This provides video, voice and flight data recording as well as satellite communications. The IRIS equipment was sent to the NTSB Vehicle Recorder Lab for analysis.
We will update this report as more information emerges.
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