Six dead in chopper crash in Hudson River, 10/04/2025

[onetrack]

Of all the failure causes, a mast bump rates highly as the main cause of this crash. It would have to be a major maintenance fault that caused a Jesus nut failure.

It appears to me, from what I've seen in videos of 206 in the air, the entire mast, rotors and main gearbox tore away in one piece. For that to happen, there would have had to have been a rotor impact with the fuselage at some point.

 

It's not unknown for tail rotors to fail, in which case all bets are off, and anything can happen from there on in. Who recalls the 1966 Bell 47G helicopter crash in central Sydney, at Circular Quay?

The Circular Quay crash was caused by a maintenance crew who left a washer off a nut on one of the tail rotor bolts. The missing washer caused tail rotor flex that eventually fractured the blade.

The crash investigators went through every rubbish bin in the aircraft workshop, until they found the missing washer. They had to find the washer, to determine whether it was left off accidentally, or if it had fractured in flight, and fell out.

 

https://www.abc.net.au/news/2018-12-10/the-helicopter-crash-that-changed-australian-aviation/10585722

[BrendAn]

33 minutes ago, onetrack said:

Of all the failure causes, a mast bump rates highly as the main cause of this crash. It would have to be a major maintenance fault that caused a Jesus nut failure.

It appears to me, from what I've seen in videos of 206 in the air, the entire mast, rotors and main gearbox tore away in one piece. For that to happen, there would have had to have been a rotor impact with the fuselage at some point.

 

It's not unknown for tail rotors to fail, in which case all bets are off, and anything can happen from there on in. Who recalls the 1966 Bell 47G helicopter crash in central Sydney, at Circular Quay?

The Circular Quay crash was caused by a maintenance crew who left a washer off a nut on one of the tail rotor bolts. The missing washer caused tail rotor flex that eventually fractured the blade.

The crash investigators went through every rubbish bin in the aircraft workshop, until they found the missing washer. They had to find the washer, to determine whether it was left off accidentally, or if it had fractured in flight, and fell out.

 

https://www.abc.net.au/news/2018-12-10/the-helicopter-crash-that-changed-australian-aviation/10585722

I would have thought gearbox seizing or bearing failure would have to be looked at too.

[Deano747]

2 hours ago, BrendAn said:

I would have thought gearbox seizing or bearing failure would have to be looked at too.

Agree.

The speed of the rotation is too fast for a tail rotor failure. 

All rotary wing pilots are trained and practice tail rotor failures (both full left and full right pedal) and while they can make life interesting, are not impossible to control. 

An aviation accident blogger interviewed a US test pilot with some 7,000 hours on rotary wing and said the mast bump theory as unlikely as there has only been 1 documented accident with mast bump on a 206 in that models history.

In that case the tail boom separated at the far end and not near the cabin in  these videos.

Also in that case, a large portion of the main rotor blade sheared off and in these videos it has been pointed out that the rotor blades appear complete and attached to the mast and what appears to be a portion of the transmission.

He, quite rightly, is saying that no-one will know until all the wreckage is recovered and inspected.

A transmission failure would give a yawing motion of that severity. 

 

 

[Thruster88]

The initial rapid yaw appears to be to the right, this would occur due to torque driving the main rotor with a boom failure. Main gearbox jammed would result in a yaw to the left?

[Thruster88]

 

Tail boom separation about 300mm aft of the bolted join, approximately where a tail rotor drive shaft bearing would be.....