N385RH

HISTORY OF FLIGHT

On October 22, 2012, at 0602 central daylight time, an Agusta SPA AW139 helicopter, N385RH, collided with the terrain following a loss of control while the helicopter was being repositioned on the Houma-Terrebonne Airport (HUM), Houma, Louisiana. One of the airline transport rated pilots was not injured and the other suffered a serious injury. The helicopter was substantially damaged. The helicopter was registered to and operated by ERA Helicopters LLC, and was being operated under the provisions of 14 Code of Federal Regulations Part 91 at the time of the accident. Visual meteorological conditions prevailed.

The accident flight crew reported they performed an aircraft preflight and reviewed the maintenance logbook prior to moving the helicopter outside to the A-5 pad. They completed the run-up and power/trend checks after which they lifted the helicopter off the ground and hovered laterally to center the helicopter on the pad. They then shut down the helicopter. Shortly after shutting down the helicopter, they were asked to move the helicopter to another pad. They started the helicopter once again, and the left seat pilot lifted the helicopter, hovered backwards, and made a right pedal turn to hover taxi to the pad.

The pilot lined the helicopter up over the edge of the pad and began a descent while moving forward. He lowered the helicopter and the main wheels touched down. He stated he was not sure if the nose wheel had fully touched down, but the helicopter began to "oscillate violently." The pilot stated he continued to lower the collective, but the vibrations and oscillations intensified. Initially thinking that they had encountered ground resonance, the pilot increased the collective to lift the helicopter off the ground. The helicopter became airborne, and the violent oscillation and vibration continued. The pilot stated he was able to move the helicopter rearward and to the left away from another helicopter that was being fueled. He initiated a left pedal turn at which time the oscillations and vibrations were so severe that the pilots' headsets came off of their heads. The helicopter entered a spin and impacted the grass hard while moving laterally to the left. The pilots shut down the helicopter and both were able to exit the helicopter on their own.

Numerous witnesses saw and heard the helicopter during the accident sequence. The witnesses described hearing an unusual noise that was described as "a compressor stall", a "whop, whop, whop", and a pulsing/surging sound. The witnesses stated the helicopter rose to an altitude between 20 and 70 feet above the ground and spun violently to the left. They stated the helicopter then descended and impacted the ground in an upright attitude.

PERSONNEL INFORMATION

The pilot-in-command held an airline transport pilot certificate with a helicopter rating. The pilot-in-command was type rated in Agusta AW139 helicopters. He was issued a first class airman medical certificate with no limitations on February 29, 2012. According to ERA the pilot had a total flight time of 3,153 hours of which 257 hours were in Agusta AW139 helicopters.

The pilot-in-command completed his initial AW139 ground school training with ERA Helicopters on February 23, 2012. He completed his initial AW139 checkride with ERA Helicopters on February 29, 2012, and his most recent proficiency check was on June 6, 2012.

The co-pilot, who was the pilot flying when the accident occurred, held an airline transport pilot certificate with multi-engine and helicopter ratings and commercial privileges for airplane single-engine land and airplane single-engine sea. a commercial pilot certificate with single-engine land and single-engine sea airplane ratings. He held a flight instructor certificate with a single-engine land, multi-engine land, helicopter, and instrument ratings. The pilot held a type rating in Sikorsky S-61 helicopters. He was issued a first class airman medical certificate with near vision limitations on March 22, 2012. According to ERA Helicopters, the pilot had a total flight time of 7,340 hours. He had a total rotorcraft time of 6,711 hours of which 25 hours were in Agusta AW139 helicopters.

The co-pilot completed his initial AW139 ground school training with ERA Helicopters on February 1, 2012. He completed his initial AW139 checkride with ERA Helicopters on March 17, 2012, and his most recent proficiency check was on August 5, 2012.

AIRCRAFT INFORMATION

N385RH was an AgustaWestland AW139, serial number (s/n) 410013. The helicopter had a total time of 2,063.3 flight hours at the time of the accident. The helicopter had a five-bladed, fully articulated main rotor system that provides lift and thrust, and a four-bladed, fully articulated tail rotor system that provides main rotor anti-torque and directional control. The helicopter was equipped with two Pratt & Whitney Canada PT6C-67C turboshaft engines. The helicopter had a dual hydraulic flight control system and the Honeywell Primus Epic integrated avionics system that contained an automatic flight control system (AFCS).

On October 18, 2012, at a helicopter total time of 2,062.2 hours, the "orange" and "white" main rotor pitch control links were adjusted. An operational check flight was conducted and the flight was signed off as being "complete and satisfactory."

On the night prior to the accident, the helicopter underwent maintenance during which "blue" main rotor damper, s/n 10568 was removed due to a reported leak. Damper s/n 1602 was installed in the "blue" main rotor blade position. An operational check flight was conducted following the maintenance. The crew from this flight stated there was a slight vibration from the main rotor. They returned to the maintenance base where they landed and shut down the helicopter. They stated that they were able to see that one of the blades had a "slight dip" in its track which they attributed to have been the cause of the vibration. They stated they informed maintenance personnel that the flight was satisfactory, and of the slight vibration and blade dip. The crew stated the helicopter was then towed into the hangar. There was no written record of the crew reporting a main rotor blade out-of track discrepancy, nor was there a main rotor track and balance performed subsequent to the operational check flight.

METEOROLOGICAL INFORMATION

At 0555, the HUM airport Automated Weather Observing System (AWOS) recorded the weather conditions as: wind 070 degrees at 3 knots; visibility 10 miles; clear sky; temperature 13 degrees Celsius; dewpoint 13 degrees Celsius; and altimeter 30.07 inches of mercury.

FLIGHT RECORDERS

Cockpit Voice Recorder (CVR)

The helicopter was equipped with a Penny & Giles MPFR combination flight data recorder and CVR. The solid state CVR recorded 2 hours of digital cockpit audio. The CVR was removed from the helicopter and sent to the NTSB Recorders Laboratory for the audio information to be extracted. The 2-hour recording contained several power interruptions, causing discontinuity in the time scale. As such, multiple correlations with the flight data recorder (FDR) were accomplished. The recording did contain a period of mechanics working on the helicopter, a maintenance test flight, movement of the helicopter out of the hangar, a repositioning flight, and the accident flight.

A partial transcript of the maintenance test flight was developed from the recording. The recording began at 0023:33 and ended at 0048:15. During the flight, the crew discussed the blade tracking issue stating it the helicopter had a "hop" to it and that they could "see it in the blades." The crew stated it looked like a track problem and they speculated that someone probably bumped trim tab.

After landing, the crew was heard having a discussion with a mechanic. The crew informed the mechanic that there was one blade that was "pretty good out of track." The stated it wasn't a damper problem and that it was just one blade. The crew then stated the operational check flight was complete and satisfactory.

At about 0537, the accident crew lifted-off the reposition the helicopter to another landing pad. Prior to the lift-off, the performed various preflight checks, started the engines, and performed the engine run checks. After shutting down the helicopter, the crew voices became distant, as if they had departed the helicopter. The CVR reordered an unidentified voice asking the crew to move the helicopter to a different landing pad. The crew agreed to reposition the helicopter.

At 0552:42, the crew began the process of starting the helicopter. The crew is heard running a checklist and starting the engines. The crew discussed that the second-in-command (SIC) would fly the helicopter. The crew communicated that the area was clear as the helicopter lifted off and maneuvered to the landing pad. As the crew is setting the helicopter down there is a rattling sound that increased in intensity. The recording continued with the crew struggling to maintain control of the helicopter as several aural warnings are sounded. The warnings included "rotor low", "rotor high", bank angle, and tail too low warnings. At 0602:02 the sound of the ground impact was recorded.

Sound Spectrum Study

A sound spectrum study was performed to examine the low frequency sound spectrum related to the main rotor operation. The AW139 helicopter is equipped with a 5-bladed main rotor system. When operating at 100% rotor speed (Nr), the rotor generated a 24.7 Hz frequency, and when operating at 102% Nr, the rotor generated a 25.2 Hz frequency. Two periods of sound recorded from the cockpit area microphone (CAM) were examined, one from the maintenance test flight and the other from the accident flight.

The 19.133 second period of sound from the maintenance test flight was extracted from the CAM and three time periods, designated as A, B, and C, of that recording were examined. Period B showed 5 d...