What happened
On June 13, 2016, a EUROCOPTER EC120, registration N372HS, landed on a hilltop composed of volcanic rock near Ajo, Arizona. After the aircraft came to a stop, the pilot exited the cockpit while the engine and main rotors were still in operation. During this time, the pilot heard an audible change in the rotor sound and observed the ground beneath the right skid giving way. This caused the helicopter to roll to the right, resulting in substantial damage to the tail boom. There were no injuries resulting from the event.
The investigation
The pilot reported that there were no mechanical failures or malfunctions regarding the engine or airframe prior to the impact that would have prevented normal operation. The weather at the time of the event was visual meteorological conditions (VMC) with a visibility of 10 statute miles and winds at 280 degrees at 3 knots.