Latest news is that blade failure on the fenestron has been ruled out following examination of the wreckage by ECF. The Aerocontractor's Dauphin fleet are now all flying again.
The helicopter in question which was equipped with a CVR, had the CVR trip off after approx. the first 5min. of the flight. French Investigators are trying to find out what could have caused this to happen. Progress of the flight up until that stage was normal.
What little is known is there was an engine failure at a cruise ht of less than 1000ft shortly after T/o. (Survivors heard a loud bang). Following the failure the helicopter was seemingly unable to maintain ht. A turnback to the helipad at Brass was initiated with the crew making a decision to pop the emergency floats, there being a very strong likelihood they would have to ditch. The helicopter did however make it back to Brass ending up in shallow water very close to the helipad.
On approach to the helipad it was seen coming in lower than normal (with floats inflated). Then in the final moments close to the pad there was a second loud bang followed by the helicopter doing one/two revolutions out of control as it fell from the sky hitting a solid container near the pad in the process. At the time of impact the no.2 engine was providing torque to the main rotor which itself was completley destroyed in the crash. Due to what witnesses saw in these final moments the initial line taken by investigators was tail rotor failure in the final seconds.
With ECF clearing the tailrotor/fenestron we eagerly await information from Turbomeca' s investigation of the engines. From the details that have emerged so far it sounds like a major mechanical failure of the no.1 engine, which may have also ultimately had some sort of detrimental effect on the 2nd engine........
Anyway this is purely conjecture - let's hope there is an announcement soon on what surfaces from the investigation on the Arriel engines in question.