N574EH

HISTORY OF FLIGHT

On March 15, 2013, about 1147 central daylight time, a Sikorsky S-76A++ helicopter, N574EH, was destroyed after ground impact near Grand Lake, Louisiana. All three occupants onboard, the pilot and two maintenance personnel, were fatally injured. The helicopter was registered to Era Helicopters LLC and was operating under the provisions of 14 Code of Federal Regulations Part 91 as a post-maintenance check flight of avionics systems. Visual meteorological conditions prevailed for the local flight, which departed from Lake Charles Regional Airport (LCH), Lake Charles, Louisiana at 1119.

At 1120, LCH tower controller instructed the pilot to report inbound to LCH at the completion of the maintenance flight. The pilot acknowledged and advised he would remain on the LCH air traffic control (ATC) frequency. At 1145, the pilot advised LCH ATC that he was about 10 miles to the south of LCH and would be returning for landing.

At 1146:57, the pilot called LCH tower controller and advised he had an emergency and would be immediately landing off the airport. At 11:47:02, the pilot called the Era Helicopters company dispatcher and advised that he had a problem and would be landing immediately. The wreckage of the helicopter was found about 5 miles southeast of the threshold for Runway 33 at LCH. The majority of the helicopter was consumed by a post-crash fire.

Several witnesses noticed the accident helicopter as it flew toward the accident site. The first witness, a helicopter pilot, stated that he observed the accident helicopter in a shallow descent as it passed just east of his house about 600 feet above ground level. He stated that the helicopter was producing an unusual, grinding noise as it passed over his house. After watching the helicopter pass by his house, he walked inside his house to avoid directly viewing a possible crash. As he walked back outside, he noticed smoke plumes to the north of his house.

A second witness, a previous Navy helicopter mechanic, recorded a cell phone video of the helicopter as it passed by his position. He stated the helicopter's rotor system sounded abnormal as it flew by, making a loud, screeching noise. He stated the helicopter appeared to slow down, then the helicopter's tail rose up and it started to spin. He heard a loud boom and saw a plume of smoke.

A third witness stated the helicopter was making a whistling type of noise as it flew toward LCH. At about 100 to 150 feet above the ground, he noticed the helicopter pitch down and then spin for about five revolutions. He stated that he did not hear any noise from the helicopter as it was spinning. After the helicopter impacted the ground, he noticed flames and smoke.

A map of witness locations and the helicopter's flight path is located in the docket for this investigation.

PERSONNEL INFORMATION

The pilot, age 69, held an airline transport pilot certificate with airplane single-engine land, rotorcraft-helicopter, and instrument helicopter ratings. According to records provided by Era Helicopters, the pilot had accumulated 22,564 hours of total flight experience, with 54 hours in the last ninety days. The pilot had accumulated 850 hours of flight experience in the make and model of the accident helicopter. On February 8-9, 2013, the pilot completed recurrent training in a SK-76 simulator, which included 8 hours of flight time. Dual engine failure/autorotation and tail rotor malfunctions were accomplished during this recurrent training.

On April 2, 2012, the pilot was issued a Class 1 time limited special issuance medical certificate, which required corrective lenses be worn for near vision. During the last examination, the pilot was evaluated for his history of myocardial infarction, angina pectoris and coronary artery disease requiring percutaneous transluminal angioplasty, hypothyroidism, and the use of medication.

AIRCRAFT INFORMATION

The Sikorsky S-76A++ helicopter has a four-bladed, fully articulated main rotor that provides helicopter lift and thrust, and a four-bladed flexible beam tail rotor (spar) that provides main rotor anti-torque and directional control. The helicopter is equipped with two Turbomeca Arriel 1S1 turboshaft engines that are positioned side-by-side behind the main transmission assembly.

The accident helicopter, serial number (S/N) 760369, was manufactured in 1990. Records show the helicopter had accumulated an aircraft total time (ATT) of 6,765.7 hours as of March 15, 2013. The No. 1 engine, S/N 3016, had a time since new (TSN) of 8361.10 hours and a time since overhaul (TSO) of 1475.11 hours as of March 15, 2013. The No. 2 engine, S/N 3508TEC, had a TSN of 6696.80 hours and a TSO of 1287.50 hours as of March 15, 2013.

METEOROLOGICAL INFORMATION

The weather observing station at LCH reported the following conditions at 1153: wind 180 degrees at 13 knots with gusts to 19 knots, visibility 10 miles, clear skies, temperature 23 degrees Celsius, dew point 14 degrees Celsius, altimeter setting 30.05.

FLIGHT RECORDERS

A solid-state cockpit voice recorder (CVR), model L3/Fairchild FA2100-1020, was recovered at the accident site and sent to the NTSB Audio Laboratory for readout. Timing of the accident flight CVR recording was aligned with timing information provided by a time-encoded ATC recording. Other transmissions in the CVR recording were used to validate the alignment of the two recordings.

A summary of the CVR is as follows:

1113: The accident flight recording began, with a sound similar to an engine starting.

1115: The pilot and a mechanic noted that the automatic flight control system (AFCS) test passed with no faults.

1120: The mechanic noted that they needed to do a power check when they returned. The pilot agreed.

1127: The mechanic asked if he could fly after the maintenance checks.

1127-1142: The pilot performed a series of turns, climbs, and descents to check the avionics, flight directors, and autopilot systems. The pilot and mechanic agreed one of the two flight directors may have had a remaining problem.

1142: The pilot asked the mechanic if he wanted to fly the helicopter. The mechanic agreed, and the pilot said he would set the helicopter up for the mechanic on a heading of 150 degrees at an altitude of 1,000 feet. The mechanic noted the helicopter was not like the Cessna 172 he had flown.

1143:00: The pilot said to the mechanic, "it is all yours…do anything you want with it."

1143:06: The mechanic asked if he needed to use the pedals. The pilot said only during power changes.

1143:17: Two high pitched tones, similar to an altitude alert, were recorded.

1143:42: The mechanic said "not quite as touchy as I thought it would be."

1143:45: The pilot said, "oh that's because I've got everything turn on."

1143:55: The pilot said, "What we'll do, we'll take these autopilots off. Take our forced trim off."

1144:04: The mechanic said, "oh yea, there we go; now I'm flying something. Okay."

1144:10: The mechanic said, "Okay, you got her."

1144:12: Two or three snapping sounds were recorded on the intercom. At the same time, the cockpit area microphone recorded a sound similar to the rotor or engine RPM increasing. The two or three snapping sounds, about 0.25 seconds in length, may have been a virtual artifact of the power removal from the CVR and not a physical sound that existed in the helicopter.

1144:13: The CVR recording ended.

For additional information on the CVR, see the Sound Spectrum Study and full transcript of the CVR in the docket for this investigation.

WRECKAGE AND IMPACT INFORMATION

Representatives from the National Transportation Safety Board (NTSB), Federal Aviation Administration (FAA), Sikorsky Aircraft Corporation (SAC), and Era Helicopters were present for the documentation and investigation of the helicopter accident site. Of the four tail rotor blades, two of the tail rotor blades ('yellow' and 'red') were fractured adjacent to the tail rotor hub; at the time of this report, these two tail rotor blades have not been located and recovered.

The helicopter came to rest upright on a southerly heading. The majority of the airframe, including the cockpit, main cabin, and forward portion of the tailboom, was either consumed or heavily heat distressed by the post-crash fire.

Three of the four main rotor blades remained connected to the main rotor hub and the main rotor blade spindles were oriented at about 11 o'clock, 2 o'clock, 5 o'clock, and 8 o'clock positions when viewed from above. The 11 o'clock blade had fractured chordwise outboard of its pitch horn but was found adjacent to the main wreckage about 6 feet away. All four main rotor blades exhibited evidence consistent with low rotational energy at ground impact. The 5 o'clock and 11 o'clock blades exhibited severe chordwise deformation of the spar consistent with exposure to extreme heat. The tip cap for the 5 o'clock blade was found separated from the blade and was found about 12 feet to the east of the main wreckage.

The majority of the main transmission case was consumed by post-crash fire, exposing its internal gears which exhibited evidence of exposure to extreme heat. The main rotor controls were continuous from the three main rotor hydraulic actuators' lower attachment fittings through the swashplate and up to the pitch control rods' connection to the pitch horns. The main rotor controls forward of the hydraulic actuators were consumed by post-crash fire, thus its continuity could not be confirmed.

The two engines were found behind the main transmission and were still covered by the engine cowling. Both engines exhibited evidence of exposure to the post-crash fire. Neither engine's axial compressor showed evidence of foreign object debris ingestion. Additionally, neither engine's free turbine exhibited evidence of blade shedding. The fuel control unit throttle block remained attached to the cable and the pointer was consistent with the shutdown position, but the throttl...