stock here: in this video, this guy spends a few thousand words talking about the “mast bump” which is one of the 2 blades hits the tail boom.
The blades were not damaged while they were autorotating on the way down. This guy says we cannot throw out the mast bump. I think we absolutely can.
The other one that everyone jumped on was the “Jesus Nut” which sounds all cool, but could be immediately thrown out because the blades were still nicely attached to the shaft.
And then a bunch of low information useful idiots jump on the idea that because he talked about getting fuel, that he ran out of gas….and idiotically that caused the helicopter to fly into pieces.
To me it does appear that the helo turned sharply to the right, but maybe I am not convinced. That said, many have suggested that the loss of the tail rotor could have caused that….because the tail rotor is what keep the Helo from rotating against the torque created by the main rotors….and this is 100% not true at cruise speeds….from Blancoliro video comments
The Helo did the strong rotation, before the tail assembly left, therefore until that point the flight yaw controls on the tail would have been contributing and not allowed that yaw at least due to the main rotor.
Also noted that the Tail Rotor Drive Shaft must have left with the tail rotor as it was not sticking out of the remainder of the boom, nor attached to the TRGB
Of note is that it wasn’t just some mounting bolts, as the whole aluminum honeycomb roof assembly left with the Main Gear Box (transmission) and rotors.
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The transmission and blades (and top of the fuselage) were still attached for a full 3 seconds after the tail boom was ripped off. This point appears to be of importance.
My top hypothesis right now is that the transmission seized. The question is how? There are sophisticated “chip sensors” in the tranny oil stream so that if a part was failing, there would be an alert, probably hours before a catastrophic failure.
There was a Bell 206-1 which had a bird strike, extreme control movement, mast bump, and the main rotor and transmission also detached. Some have claimed these accidents to be almost exact….however, in the Hudson event, the whole roof structure of the Helo was still attached. The aussie report is incredibly disappointing with its lack of picture evidence and how the tranny and rotors looked.
https://www.atsb.gov.au/sites/default/files/2023-05/AO-2022-034%20Final.pdf
Here is the first video
Juan Blancoliro has a video with sound amplified and synced to the video, I will put that at the far bottom.
An explosive start of this all would likely leave evidence. The chance that it was a hit on this Siemens exec is still large. There is one other instance of a nearly similar accident in the records and this guy talks about that and shows pictures. In that accident, the fuselage tp also left with the transmission. But the L4 version (this one) was built stronger and there has never been an instance of a failure like this in the L4.
—————– Comment from a Helo pilot who “flew the hell out of these airframes”
@erikt2918
4 hours agoYou’re describing a sprag clutch. When engine power suddenly stops, such as an engine failure, or engine drive shaft failure, the rotor blades continue to spin and a pilot can lower the collective and enter autorotation. However, if the transmission has seized and thus stopped rotation, that sprag clutch will be part of that failure. In the Army, I flew the Bell OH-58 and the UH-1H. Prior to this I was an Army helicopter mechanic. I have never bumped the mast in any Bell helicopter and I flew the snot out of these airframes. They are incredibly robust and durable. Not even in flight school, did I ever bump a mast. I’ve been yankin’ and bankin’ in the desert over hills and through canyons in several parts of the world. If I had bumped the mast, there are tell-tale signs on the mast that would have given me away. My point is this, the Bell 206-L4 is not as fragile as you describe. Incorrect inputs after a tail rotor separation wouldn’t be enough to cause what we see in the video. By the way, the tail rotor in forward flight is barely doing anything. It’s basically neutral, so if it suddenly came off, or the tail rotor drive had failed, not much would happen. The airframe would be “weather-vaned” into the relative wind. It’s a completely survivable failure. You simply keep your speed up and do a run-on landing, usually on a runway or taxiway. In flight training and on every checkride, we practice many tail rotor malfunctions- loss of tail rotor effectiveness, stuck pedal, loss of tail rotor drive shaft, loss of tail rotor components, etc. None of these failures will result in the fuselage folding and snapping off the tailboom. I believe the transmission seized and that sudden stoppage caused rotation of the airframe in multiple axises simultaneously causing the tail rotor to depart, the tailboom to snap, the transmission to rip from roof and depart with the mast and rotor blades still intact and spinning together. I also believe that the pilot had very little warning, if any. It was not his fault.
————————– Comment 2 of note
@Jetjockgordo
1 hour agoI wouldn’t take much stock in the mast being bent coming out of the transmission because that could be due to impact forces with the ground or water. The lack of damage of the mast where the teetering yoke would make contact with the mast makes the theory of mast bumping almost impossible. I worked for AEL in 2013 and know about the Manchester crash and they lost attitude reference while on short final to their base and the aircraft started to do an almost zero airspeed spin and with gyroscopic precession and nutation of the main rotor system (and possibly the tail rotor system applying forces through the tail boom), the movement of the fuselage ended up being out of phase with the movement of the main rotor causing a structural overload. This can happen with the mast remaining mostly perpendicular to the main rotor plane of rotation. In the NYC crash there were significant aerodynamic forces at play because of the 110kts of airspeed at the moment of the tail boom failing and the structure likely started to fail at the A pillar (not much to that juncture) transferring the loads to the B pillar then to the C section attach points. In the AEL crash there was no evidence that the teeter yoke made contact with the mast. Gyroscopic precession and nutation of a rotor system can apply some immense loads at its axis (mast) without exceeding the teetering limits of the rotor attach point. Blancolerio has a video that has been synced to sound that was adjusted for sound travel delay and was recorded at the moment of the upset and it sure sounds like the tail rotor drive shaft beating against the tail boom. It has a very resonant tone to it which the hollow tail boom would provide. The sound begins a second or so before the aircraft starts to rotate and the tail boom departs. Could this be a tail rotor driveshaft failure of some kind that causes the structural failure of the tail boom? Since the tail boom is a fully monocoque design it’s wouldn’t take much damage to structure to fail while under load because of the anti-torque aerodynamic loading of the vertical fins during cruise flight. The way I see it, the driveshaft failed for some reason causing an initial yaw to the right and with damage to the tail boom skin from the flailing driveshaft and heavy aerodynamic loading of the vertical stabilizers, the tail boom failed. With the fuselage free to rotate it was just a matter of seconds that fuselage succumbs to moving out of sync with the now precessing and nutating rotor system that causes the A pillars (my opinion the weakest point) to start failing and the cascading failure of the upper structure begins.Show less
Regarding the carbon composite (not standard aluminum) blades – at 17:47 you can see the trailing edge is split (delaminated) from the major blade fracture to the tip. (In this video there is a line/rope tied around the outer section, for the crane lift, that pulls the edges back together. There’s later video when that rope is removed, that shows the delamination better). While this could just have been water impact damage, what if that trailing edge delamination started in level cruise flight? It would cause a major tracking issue. (One blade much higher than the other). Maybe even extreme enough to cause mast bumping without any other flight dynamics needing to be involved in that. Vibration severe enough to break the tail boom and eventually the roof/transmission tears off. (I would think the forward cruise speed would add energy to the tracking imbalance). Blanco published the in flight breakup video with synchronised sound. The unusual sound started a second before the yaw & tail boom separation and continues until roof/transmission separation. The sound is very like the sound a helicopter makes in a high G “airshow maneuver” such a pulling out of a dive. Obviously this wasn’t pulling out of a dive, it was in level flight but it could easily make a sound like that if a main blade trailing edge delaminated.
———————— From the Blancoliro video this comment
@skyblot741
5 days agoI think it is unwise to draw conclusions from that audio with it having been synchronised and enhanced. Some observations about the Bell 206L helicopters. As has been indicated, main rotor RPM is 394, tail rotor RPM is 2550, but main driveshaft and tail rotor drive shaft RPM is 6016. The main rotor rotates anti-clockwise when viewed from above, when under power the cabin tries to yaw in the (nose) right direction. This yaw is counteracted by the tail rotor and the vertical stabilisers providing a nose left yaw force. In the hover and low speed this is provided by the tail rotor, in cruise flight it is predominantly the vertical stabilisers providing the force. If you fly in a helicopter you can witness this, in hover the pilot has significant left pedal applied, in cruise the pedals are close to neutral. The first question to answer is “which way does the cabin yaw?” I think I see a right yaw, but it’s hard to tell. IF it is a right yaw, that tells me the engine was developing significant power and that the transmission was working as designed, and the cabin yaw was a response to sudden loss of the anti-torque force. Since the tail rotor is doing very little work, loss of tail rotor drive has little effect on yaw in cruise flight. Next option is a structural failure like the tailboom and/or vertical stabiliser breaking off. IF the yaw was to the left that would indicate a transmission seizure of some sort. In both cases the separation of the cabin and the main rotor/pylon/cabin roof structure is most likely a result of the physical forces of the tumbling cabin and rotor. The NTSB will quickly determine the broad cause, the details will take time and patience. Meanwhile a lot of 206 operators will be wondering what they should be paying more attention to…
Good images in this. It looks like no one is in charge.
From News 12, at 1:33 they state that the tail rotor system was recovered, and yet except for the stabilizers (which are like halfway back on the “mast”) there is nothing like the main mast or tail rotor shown anywhere…..lead in the conspiracies