What happened
On January 28, 2018, an Airbus Helicopters EC 130 T2, registration N894GT, was performing a Part 135 air ambulance flight in Memphis, Tennessee. While approaching the rooftop heliport at Regional One Health Medical Center, the pilot encountered a left crosswind and adjusted the collective pitch control friction three times to facilitate necessary control inputs.
After landing the helicopter, the pilot began the after-landing checklist. The pilot turned the throttle twist grip from the "FLY" position to "IDLE," believing the collective lock had been engaged. While the pilot was reaching for the clock start button, the collective unexpectedly moved upward, causing the helicopter to become airborne. The pilot immediately attempted to regain control by grabbing the cyclic and collective and returning the twist grip to the "FLY" position. This resulted in a hard landing that activated the emergency locator transmitter (ELT).
There were no injuries to the pilot, flight nurse, flight paramedic, or the patient.
The investigation
An examination of the aircraft revealed minor damage, including deformed landing gear cross tubes and dents in the forward and aft belly panels. Security camera footage and engine data recorder (EDR) data confirmed that the collective rose from an unlocked position, causing the engine to transition from "IDLE" to "FLIGHT."
Investigators found that two days prior to the accident, a mechanic had converted the helicopter from a dual-pilot to a single-pilot configuration by removing the right seat flight controls. During a post-incident inspection, the mechanic found that the collective was improperly balanced; when the mechanic released the collective from a full-down position, it climbed unassisted to the mid-travel position. The upward spring force was approximately twice the required amount.