S-76C+ Mystery Crash

[fintastic]

As you may know, a commercially operating S-76C+ helicopter crashed into Baltic Sea in August minutes after taking off from Tallinn, Estonia en route to Helsinki, Finland. All 12 pax, including two US citizens, and 2 crew appear to have survived the initial impact but were confirmed to have drowned as the helicopter went down.

 

The submerged wreck was located and brought to surface soon after, and the flight data recorder has been recovered and analyzed in full. Estonian accident investigation board has now released their initial findings, and in a nutshell, they are baffled. Board chair was quoted saying "we know what happened, but can't tell why". They have ruled out terrorism or collision, though.

 

Based on ATC radar and FDR data, trouble began when the aircraft travelling at 150 mph suddenly surged upward, gaining 60 meters in altitude in just 1.5 secs. Just seconds later it was literally suspended in mid-air in an extreme nose-up attitude of 60-70 degrees.

 

In another 10 seconds, the craft was descending rapidly while rotating around its vertical axis at a rate of 2.5 secs per, making 13 full circles before impacting in sea. The pilot was heard issuing a mayday call, and at one stage asking "did we lose the tail?" Those were apparently his last words.

 

As the aircraft was recovered, it was found that the entire tail section had in fact separated from the main body, although it was still attached to it by cabling. It was said to be unclear however whether this took place in air or on impact. Rotor blades had been partly lost as well, however information released so far is that they separated at impact. Gearbox is said have been intact as well, however it has been sent to manufacturer for further inspection.

 

On the final incoming flight to Tallinn, an Estonian passenger seated on board claimed the aircraft had vibrated excessively. He also claims he overheard the pilots discussing it in cockpit. Apparently it wasn't anything they would have rated significant, though, as I can't imagine them taking off for the return trip in case there was any doubt of its safety.

 

Anyone care to hazard a guess as to the causes of the accident? My understanding is that there have been other "mystery" crashes involving the S-76 elsewhere as well, namely North Sea and Gulf of Mexico? Any clues to be found there?

[mrose]

Thanks Finrotor for this important post.

 

The S-76 has had it's issues in the past.  Reading this adds fire to my pursuit of developing a wireless/wired HUMS vibration analysis technology.  For those of you unfamilar with HUMS, it is a spectoral vibration monitor and logging system where the maint. crew and/or pilot can view an "ultrasound" of the ships engine and dynamic components.  If something goes bump you have a resource that allows "on-the-fly" diagnostics.

 

It's like a full time Chadwick, at the heart of the system is a new crystal sensor that outputs a full spectrum of freqs and bandwidths, like your graphic equalizer on a good boom box.

 

These sensors are mounted around onm critical components.

 

Add benchmark normal vibration levels and Wa La, your looking into your gearboxes, hanger bearings, engine - the works.  No more black magic guessing.  It is truely amazing the results they are having with this tool.

 

This stuff is real guys and you heavy ship Pilots need to know more about it.  Get your bosses and maint. chief to attend the new HAI class this Feb. in Dallas and get moving on this ASAP.

 

The armed forces are in a pell mell race to install these systems on everthing with rotors so why not you?

 

Beyond this the Navy has let reseach contracts to add the wireless sensors in the blades, sleeves - you name it, with "energy harvesting" powered micro sensors sensing torque, vibration and on- the-fly strain capture.  This system in std equioment on the S-92 and other ships, why not all S-76's?

 

Kind Regards mrose