Eurocopter AS350B3 crash near Folsom, CA, United States

HISTORY OF FLIGHTOn October 24, 2015, at 1633 Pacific daylight time, an American Eurocopter AS350B3 helicopter, N911WL, landed hard during a practice autorotation near Folsom, California. The flight instructor, pilot undergoing instruction (PUI), and tactical flight officer (TFO) were not injured; the helicopter sustained substantial damage. The helicopter was registered to Placer County, and operated by the Placer County Sheriff's Department, as a public aircraft flight. Visual meteorological conditions prevailed, and a company flight plan had been filed. The instructional flight departed Mc Clellan Airfield, Sacramento, California, at 1618. The purpose of the flight was to perform patrol missions, in addition to providing training for the PUI, who had recently been hired by the Sheriff's department. This was his first patrol training flight, and he was seated in the front left seat, with the flight instructor in the front right, and the TFO in the rear jump seat. The plan was to introduce the PUI to the helicopters systems while on patrol, and then perform a series of straight-in, 180°, and "enhanced" autorotation's. The flight instructor stated that an enhanced autorotation is a maneuver where a point is picked for an emergency landing, and the pilot is tasked with landing the helicopter at that point using whatever maneuvers are necessary. The crew departed from their base at Auburn Municipal Airport, Auburn, California about 1230, and initially performed routine patrol work. Once completed, they then transitioned to a series of autorotation's with power recoveries in a flat field, all of which were uneventful. They then landed at Mc Clellan Airfield, and serviced the helicopter with about 120 gallons of fuel. After departure, they flew to a peninsula on the northern shore of the Folsom Lake Reservoir with the intention of performing more enhanced autorotation training. The peninsula, which according to the flight instructor was an area for training approved by the department, was normally partially submerged in water but due to drought conditions, was fully exposed. They reported surveying the area and beginning the maneuver at 2,500 ft mean sea level (about 2,100 ft above the lake surface). The flight instructor stated that he was the pilot-in-command, and that the PUI was "shadowing" the controls. They surveyed the area and then performed an enhanced autorotation with a power recovery to the dry lakebed. The flight instructor stated that during this maneuver the PUI appeared overwhelmed. They then set up for another approach to the peninsula, and the flight instructor told him to just track rotor RPM and not to worry about foot pedal control, or aircraft attitude, as he demonstrated that rotor RPM could be controlled with both the cyclic and collective. The flight instructor reported that at about 1,000 ft agl, he felt the PUI was inadvertently hindering the controls, and he reached over and moved the PUI's hands away from the controls. The flight instructor stated that he was not concerned, and in his experience, this was not unusual while providing training. The rotor RPM remained within limits during the remainder of the descent, and as they approached 100 ft agl, the flight instructor verbalized his intentions to perform a power recovery, and began by turning the throttle twist grip control from idle to flight, while simultaneously initiating the flare. As the flare progressed he did not hear the engine fully regain its speed, and he checked the instruments, observing that the engine and rotor RPM needles were still "split". They were between 10 and 25 ft from the ground and he prepared for a full touchdown landing, but by now the helicopter had moved forward to an area of down-sloping terrain. He did not want to land in an unusual attitude, so aimed to touch down flat on the skids relative to the slope. He then pulled the collective control hard just before impact to cushion the landing. By now the engine had recovered to full operating speed and he immediately applied collective control lifting the helicopter back off the ground. He then maneuvered the helicopter for landing about 100 ft forward. After landing, he exited the helicopter and discovered that the aft airframe was wrinkled, and the tailboom had bent downwards at its intersection with the aft bulkhead. He was surprised the helicopter had sustained this damage because while the landing was hard, it did not feel hard enough to cause structural damage. He recounted having performed many autorotation's before, all without anomalies, and that this time the engine sound did not match his throttle control inputs. The flight instructor reported that during the autorotation he was focused on audio and visual external clues as he had done in the past, rather than examining the instruments during the descent. He did not hear any audible alerts during the flight, did not notice any lights on the annunciator panel, and all gauges were "in the green". The PUI recounted similar observations, and stated that the flight instructor initially asked him if he would like to perform the final autorotation, but he was not happy doing so. They agreed that the flight instructor would fly the autorotation, and he would shadow the controls. During the descent the PUI kept his right hand on his lap, and lightly held the collective with his left hand. At one point when he was watching the Nr gauge, the cyclic brushed against his hand, and the flight instructor asked what he was doing. The flight instructor then physically moved his right hand onto his lap, but at no point was there any interference with the flight controls. They then made a final right turn towards the landing zone, and as they approached 100 ft agl, the flight instructor stated that he was applying throttle, and the PUI felt the twist grip move in his hands. The PUI then released his hand completely from the twist grip, and as they approached the hilltop which was the landing spot, the flight instructor initiated the flare. The PUI stated that it was at this point that he had a "seat of the pants" sensation that something was wrong. The flight instructor verbalized to that effect, and the PUI felt that he should be getting a sense that power was being applied, but he was not. They were about 20 ft agl as the terrain fell away, and he started to hear a change in engine tone, but the helicopter then began to rapidly sink. He saw the flight instructor then quickly pull up on the collective, and he was relieved as this seemed to be the appropriate maneuverer. The helicopter then landed hard, and started tipping forward as the engine sound continued to change. He became concerned that the helicopter may roll forward, but instead it lifted back up into the air under what now appeared to be power. He did not recall any audible warnings or annunciator panel lights during the descent. Accident Location The accident site was composed of rolling hills, covered in dry grass, and interspersed with rocks. The intended landing zone was on a pinnacle, about 100 ft from where the helicopter came to rest. The terrain from the top of the pinnacle to the resting location was on a downward slope of about 4°, and the site was at an elevation of about 455 ft above sea level. The site was about 2 miles across the lake from the City of Folsom, however, the closest access via automobile from Folsom would have required a drive of about 27 miles on paved and unpaved roads, followed by an off-road drive of about 1 mile. The helicopter was recovered from the accident site the following day under the supervision of the Sheriff's department, and the accident was reported to the National Transportation Safety Board three days later. PERSONNEL INFORMATIONFlight Instructor The flight instructor had been a member of the air support unit since 2000; he was the chief, and only helicopter pilot for the Sheriff's department. He attended ground, flight, and r