Very strange initial findings in PHI S-76 helicopter crash

PHI S-76.jpeg

The very nasty fatal loss of a PHI Sikorsky S-76C++ helicopter in Louisana last month is perplexing the rotary world. The NTSB just came out with its initial findings which are as close to mystifying as you’ll ever see. Essentially there is no evidence of anything being wrong with the aircraft, the manner of the flight, the conditions, etc.

The question is what is the “loud noise” followed by “a substantial increase in the background noise level” on the CVR, just before the engine power was reduced (but not by any kind of mechanical failure as far as they can tell.) Full report below. Pprune discussion here.

National Transportation Safety Board

Washington, DC 20594

February 5, 2009

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NTSB ISSUES UPDATE ON INVESTIGATION INTO CRASH OF A PHI SIKORSKY HELICOPTER NEAR MORGAN CITY, LOUISIANA

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In its continuing investigation of the January 4, 2009, fatal accident involving a Sikorsky S-76C++ helicopter, operated by PHI, Inc., that crashed in a swamp near Morgan City, Louisiana (NTSB Accident Number CEN09MA117), the National Transportation Safety Board has developed the following factual information:

A detailed examination of the wreckage and components has not revealed any evidence of pre-impact engine, transmission, hydraulic servo, or systems failures.  

Additionally, no evidence of a midair collision, or in- flight rotorblade failure was found.  An adequate amount of fuel was on board the helicopter at the time of the accident.  No evidence of fuel starvation, a bird strike or electrical arcing has been found.

Data from the Penny & Giles combination flight data recorder

(FDR) and cockpit voice recorder (CVR) were analyzed at the NTSB’s Recorders Laboratory with download assistance from the manufacturer’s facility in England, and the US Army Safety Center in Fort Rucker, Alabama.  Both recorders

captured the accident flight.    

Analysis of FDR data indicates that the helicopter was cruising at 138 knots, at an altitude of about 700 feet above the ground.  The CVR indicates a loud noise followed by a substantial increase in the background noise level that was recorded on both intercom microphones and area microphone. About one second after the loud noise, the torque of both engines drops simultaneously to near zero.  

The engine and rotor parameters recorded by the FDR and recorded sounds from the CVR show a simultaneous drop in RPMs over the next several seconds.  The airspeed decreased slightly for the next 10 seconds while the helicopter descended. The engine continued to operate at low power levels until the end of the recorded data.

The non-volatile memory (NVM) from the engines’ digital engine control units was successfully downloaded, and no faults were recorded.  Additionally, NVM from the enhanced ground proximity warning system was successfully downloaded, and was consistent with DFDR data.  

All three main rotor hydraulic servos and the tail rotor servo were found in good condition with no external leakage or damage.  Functional tests and tear downs revealed no problems.  Hydraulic reservoirs were full and no leakage was found.

 

The main rotor transmission had no external damage and the rotor shafts were free to rotate.  The transmission case was opened and all internal components appeared normal with no

damage.   

 

The engines were examined.  They showed evidence of having been producing power at impact.  No anomalies were noted that would have prevented normal operation.  

Portions of the windscreen and composite center post have been recovered and sent to the NTSB laboratory in Washington, DC for further examination and analysis of the composite structure and windscreen.

Parties to the investigation include the FAA, PHI, Turbomeca, and Sikorsky.

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4 Responses to Very strange initial findings in PHI S-76 helicopter crash

  1. Erwin February 21, 2009 at 5:38 pm #

    I heard this particular aircraft had the STC for the plastic windshield and theyre thinking that some sort of bird impacted the windshield(which explains the loud bang), broke thru and took out the throttle quadrant which killed the engines and the rest is history.

  2. this site January 29, 2010 at 11:19 pm #

    This could have been prevented… I hope the proper people will properly discover the cause of the crash, so that such a tragedy can actually be prevented in the future

  3. John Michael Dique July 20, 2010 at 9:23 am #

    What about an electromagnetic effect ?Please don’t laugh.
    If a sabot was lobbed in the window, and then out the other[not hard with todays guidance systems] with an Electro-Magnetic Pulse Weapon attached,[activated by a tiny explosive charge, that drives a highly modified Van De Graff Generator] then that would provide:
    1.The audible “bang”
    2.The ensuing microphone noise, as the electronics go haywire,
    3.and power failure, with no obvious damage.

  4. Ron Paungan October 16, 2013 at 3:11 am #

    Friends,
    Between 2004-2005, there was an incident involving the same aircraft where the pilot did an emergency landing. This happened in the Philippines with an international company servicing the oil and gas industry. When i was asked to be involved in the initial investigation being on the client side, we saw that the engine cap popped out and the thread is in a mess. It was not a tight fit prompting me to ask the source of that part and that they investigate from there. This could be a possibility.
    I have not received any conclusive result of that investigation.
    Ron.

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