History of Flight
On July 3, 2014, at 1715 Pacific daylight time, an American Eurocopter Corp. AS350B3 helicopter, registration N832PA, landed hard and rolled over on a mountain ridge approximately 54 miles east of Fallon, Nevada. The helicopter was operated by Papillon Grand Canyon Helicopters as a public-use aircraft under an exclusive contract to the Bureau of Land Management. Visual meteorological conditions prevailed, and a local flight plan had been filed.
The pilot reported positioning the helicopter with an external load into a mountain supply drop zone at an elevation of 8,600 feet mean sea level. As the helicopter approached the drop zone, with the load about 10 feet above the ground, the nose yawed left and descended. The pilot set the load down, but the helicopter continued rotating left, descended, landed hard, and rolled over.
Witnesses stated the helicopter was about 200 feet above ground level with a 100-foot long line attached to the external load. When the load was about 50 feet above the ground, the helicopter began swaying, dropped vertically about 20 feet, then rotated clockwise. Upon ground contact, rotation accelerated, the helicopter landed hard, rotor blades struck the ground and fragmented, and the helicopter rolled onto its right side. A small fire erupted from the engine compartment and extinguished itself. Ground personnel assisted the pilot's egress.
The pilot had completed seven external load drops at a location designated H1. The drop location was moved about 100 yards downslope on the leeward side of the ridge for the final loads; the accident occurred during the first drop at the revised location.
Personnel Information
The pilot, age 51, held a commercial pilot certificate with rotorcraft-helicopter rating issued March 30, 2004, and a flight instructor certificate with helicopter rating issued December 3, 2009. He held a second-class medical certificate dated January 7, 2014, with a limitation requiring corrective lenses. The pilot reported 9,585 flight hours, including 319 hours in the accident helicopter make and model, and 20 hours in the previous 30 days. His most recent FAR part 135 flight check was conducted on April 17, 2014, in an AS350B3e.
Aircraft Information
The six-seat, single-engine helicopter, serial number 7307, was manufactured in 2012. It was powered by a Turbomeca Arriel 2D, 950-hp engine, serial number 50051. It was equipped with skid landing gear and a digital external load scale mounted below the left collective control. The pilot did not recall the load scale reading for the accident load. Maintenance records showed a 300-hour inspection completed on April 27, 2014, at 795.5 total hours, and a daily inspection on June 30, 2014. Airframe total time was 874 hours at the time of the accident.
The pilot's load calculation, performed at 0700 on the accident day using an equipped weight of 3,148 lbs, 500 lbs of fuel, pilot weight of 200 lbs, operating at 9,000 feet msl, and OAT of 26°C, yielded a maximum allowable external payload of 852 lbs for hover out of ground effect (HOGE). Technical representatives from Airbus Helicopters calculated a maximum external load of 1,022 lbs under conditions of 3,148 lbs equipped weight, 250 lbs fuel, 200 lbs pilot, 8,600 feet msl, and 30°C OAT. The actual external load, weighed on-scene, was configured as a two-bundle daisy chain totalling 942 lbs including the 100-foot line and hook.
Meteorological Information
Weather observations were recorded by the firefighting crew at the cargo drop zone. Observations at 1400, 1500, 1600, and 1700 PDT reported temperatures around 80°F, relative humidity 10-13%, wind from the south-southwest at 3-10 mph with gusts to 20 mph. The closest official station, Fallon, NV (KNFL), about 54 miles west, reported at 1656 and 1756 PDT wind from 300-310° at 7-9 knots gusting to 14 knots, 10 miles visibility, and temperature 37°C. An upper air sounding for 1700 PDT indicated an unstable environment, gusty winds near the ridge line, and conditions conducive to mountain wave turbulence with possible updrafts and downdrafts of +/-1500 feet per minute at 10,000 feet msl.
Wreckage and Impact Information
The main wreckage rested on a barren hilltop on its right side. The right main landing skid bent and separated from the upper cross tube; the left skid remained attached. The tail boom separated about 12 inches forward of the tail rotor gearbox; both tail rotor blades separated from the hub and showed ground impact damage. All three main rotor blades remained attached but displayed ground impact damage. The cargo long line had released from the external hook. The engine cowling and surrounding area showed soot discoloration from a post-crash fire. The wreckage was recovered to a facility in Phoenix, Arizona.
A full airframe and engine examination was performed on July 24, 2014. The helicopter was configured for single-pilot left-side controls with an extended arm rest and cargo mirrors. Flight control continuity was confirmed from cockpit inputs to main and tail rotor servos. The anti-torque pedals were positioned with right pedal forward and could not be moved until tail rotor servo accumulator pressure was released. Both hydraulic pumps operated normally. The engine displayed thermal damage; the gas generator could not be turned by hand. The engine data recorder (EDR) was removed for download.
Tests and Research
On August 28, 2014, the EDR was downloaded, containing the last 50 hours of engine parameters recorded at 1 Hz. The power-on time for the accident flight was 91 minutes. Data showed a steady rise of the collective over 7 seconds starting 16 seconds before the end of recorded data, accompanied by right antitorque pedal movement beyond 70%, N1 acceleration to 102.5%, fuel flow increase to 222 LPh, and N2 droop. At 11 seconds before the end, main rotor rpm reached a low of 378 rpm. One second before the end, a fault consistent with main rotor ground impact was detected.