History of Flight
On July 7, 2018, at about 2123 central daylight time, a Eurocopter Deutschland GMBH EC135 P1 helicopter, registration N312SA, impacted terrain during an autorotation near Chicago, Illinois. The pilot, flight paramedic, and flight nurse sustained serious injuries, while the patient was not injured. The helicopter sustained substantial damage to the fuselage, tailboom, and main rotor blades.
The helicopter was registered to Bennett Aviation, LLC, Elmhurst, Illinois, and operated by Pentastar Aviation Charter under Title 14 Code of Federal Regulations Part 135 as an air ambulance flight. Night visual meteorological conditions prevailed, and the flight operated under a visual flight rules flight plan. The flight departed St. Mary Medical Center, Hobart, Indiana, at 2110, destined for Advocate Christ Medical Center, Oak Lawn, Illinois.
Helicopter satellite tracking data and air traffic control information revealed the helicopter was traveling northwest from St. Mary Medical Center at about 1,000 ft above ground level. About 5 miles southeast of Advocate Christ Medical Center, the helicopter turned right after the pilot requested to divert to Gary International Airport (GYY), Gary, Indiana. About a minute 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 Highway 94 and Interstate Highway 57 interchange.
Surveillance video from a Chicago Transit Authority rail platform depicted the helicopter during the final phase of the autorotation and impact. The video showed a fire near the No. 2 (right) engine during the autorotation, and a flame burst was observed after impact.
The pilot recalled portions of the flight. After departure, he climbed to 1,700 ft mean sea level. About 5 miles west of GYY, he contacted Chicago Midway International Airport and noticed a "Twist Grip" warning on the left engine side warning panel. He also noticed a second indication but could not recall the specific warning. He grabbed each engine throttle twist grip to verify position and did not notice significant changes. The pilot decided he did not have enough time to troubleshoot before landing at the hospital and informed the medical crew they would divert to GYY, handing them the emergency checklist.
As the pilot executed the turn to GYY, he noticed the No. 2 engine N1 indication no longer matched the No. 1 engine; it was lower and oscillating. Within about 1 minute, he heard the low rotor RPM horn and lowered the collective. The pilot located a dark spot for autorotation. He felt the tail oscillate right and back and heard engine speed changes. At about 200 ft agl, he made adjustments to collective and cyclic. After impact, the flight paramedic mentioned fire, and the pilot saw a fire near the No. 2 engine.
Personnel Information
The pilot was hired by Pentastar in August 2016 and primarily flew the EC135 P2+ helicopter. His most recent Part 135 competency check was completed March 31, 2018, in the EC135 P2+, which had a different cockpit display than the accident EC135 P1. At the time of the accident, he had about 319 flight hours in the EC135 P2+ and about 11 total hours in the EC135 P1. He completed the operator's online EC135 P1 differences training on February 18, 2018, which included differences in cockpit displays, flight limit indicators, and twist grip controls. He also completed hands-on training with other pilots and familiarization flights. No simulator training for the EC135 P1 was available.
Aircraft Information
The helicopter was maintained according to the manufacturer's inspection program, with the most recent inspection on April 2, 2018. It had accrued 6,555.4 flight hours. The helicopter was not equipped or certified for instrument flight rules operations. The engines were equipped with Electronic Engine Control (EEC). The twist-grip throttles were mounted on the collective: forward for No. 1 (left) engine and aft for No. 2 (right) engine. Normal flight was conducted with throttles in the neutral position, allowing EECs to control engines. If a throttle was rolled out of neutral, two annunciator lights (ENG MANUAL and TWIST GRIP) and a yellow master caution would illuminate. The rotorcraft flight manual provided specific procedures for returning the throttle to neutral and warned to avoid quick twist grip rotations.
Wreckage and Impact Information
Examination of the accident site revealed the initial impact was consistent with the tail bumper contacting terrain, followed by the landing gear skids and fuselage. The left landing gear skid separated. The fuselage was crushed upward, and the fenestron structure separated near the tailboom attachment. The helicopter rotated 180° and came to rest upright. Three main rotor blades displayed fractures near the root; one blade was relatively undamaged. The pilot and paramedic seats were fully attenuated; the flight nurse seat had two floor legs fractured and seat back separated.
The ENG 1 twist grip was in the “Max” position, and the ENG 2 twist grip was in the near “Max” position. Both engine mode select switches were in the “normal” position with guards in place. The engine control switches were in the “off” position. Thermal damage was noted on the No. 2 engine and main transmission cowling. Both engines had missing outer halves of power turbine blades and holes in exhaust stubs. Engines and FADEC components were sent to Pratt & Whitney Canada for examination.
Communications
Audio recordings captured cockpit and air-to-ground communications. Key excerpts include the pilot informing the crew of a manual twist grip, requesting return to Gary, and declaring mayday. The audio also captured warning gongs and rotor RPM alarms leading up to impact.
Flight Recorders
The helicopter was equipped with an Outerlink IRIS flight data monitoring device. Data and audio were extracted. Video imagery was out of focus and not useful; the camera focus ring had only one set screw, and the operator had not been notified of a related service bulletin.
Survival Aspects
The pilot’s seat lower composite structure was fractured, and the shoulder harness inertial reel separated. The pilot sustained a head laceration and spinal fractures.
Tests and Research
Examination of the twist-grip throttles confirmed continuity. The No. 1 engine throttle was unable to move; the No. 2 was free to rotate. Impact-related damage was noted from the co-pilot collective control gearbox. The master caution light had two broken filaments in the top bulbs. The collective assembly was examined at Airbus, where impact damage was noted.