No expert here. I don't have any time in a 206, just a 205. I was investigator in over 1000 vehicle accidents as a State Trooper. LOL. I would not argue against your idea that a "progressive tear-away" could be a feasible explanation. I saw the video of the two large helicopters in Kuwait a few decades ago. They were straight & level in line abreast (side-by-side). Then they got inches too close and rotor tips started striking, barely. Within one second, the tailboom had folded and flew off the aircraft sending the fuselage spinning to the ground. The tailboom is very, very light and weak. It HAS to be. My point is, in the first few milliseconds of a "tear-away" event like you describe, the boom could be broken off.

Recall that the rotor head teeters, so it is possible that while still rotating as a whole, the mast teetered a little relative to the rotor assembly, so that it all came back into balance again. As the top deck pitch links will have all broken, the swashplate was likely still torsionally fixed to the mast, so both blades could go to their low pitch stop, which would aid their autorotation. The mast and transmission would definately stabilize the whole assembly in the feather axis of both blades, so the whole thing could have been very stable, and ideal for autorotation. The rotor assembly + mast + transmission appears in the video to be autorotating nicely.

That's what I saw. Even the SDR history of a chip light in the past doesn't steer me towards the transmission - there hasn't ever been a catastrophic seizure of a 206 MRGB as far as I know. Even the SDR about the chip light - I've had many a XMSN CHIP in these things when I used to fly them and never was worried that the thing was gonna crap out. Pretty robust and simple design, well proven.

Yep, I'm thinking the cabin roof maybe had its strength degraded over the years, possibly corrosion, possibly sheet metal repairs, possibly damage during engine removals/installs?

Also amazing was that nobody got hit by any of the shrapnel and there were a lot of people around. One guy's tool box got nailed (it was in a hangar), at least one bird was killed, and a piece wound up in a shop window across the street from the plant.

Looks like they found rotor attached to trans and all.
it’s on Ny post.

https://nypost.com/2025/04/14/us-new...-hudson-river/

Image of the assembly included.

https://cimg4.ibsrv.net/gimg/pprune....72771e453.jpeg

If I was a TSB investigator, I would be heading in this direction. I've had collective bounce in a 206L induced by turbulence and it felt like the helicopter was going to break apart in flight. I was happily flying straight and level and then pretty much instantly bouncing up and down with my seat belt and shoulder harness holding me in from the extreme ups and downs. When bouncing like that, your instinct is to hold on to the collective which actually makes things worse. To get out of it, I used the palm my hand and pushed the collective down. This stopped the bounce pretty much instantly. I always make sure I've got a bit of collective friction on now... Here's another report from someone who wasn't so fortunate --> https://www.tsb.gc.ca/eng/rapports-r.../a08p0265.html
We had van Horn blades on a 206B and the premature wear on bearings and flight controls in less than 1000 hours was like nothing we'd ever seen on 30k + hours of 206B time in our fleet. We no longer operate VH blades on anything.

Thanks, Senior Pilot ... I was struggling to extract an image from the article.

But what would be the initiator/excitor in this case?

Wow, That picture is quite unexpected. The entire gearbox and mounting looks unscathed. Metal fatigue and or corrosion may have set in.

Not really. The roof itself is a honeycomb panel and is either serviceable or its not. The nodal beam assembly bolts through the roof panel to a separate roof beam attached to the underside of the roof panel. The footprint of that roof beam does not cover the entire roof panel and only covers approximately what is shown still attached in the photo above. The remaining roof panel on the fuselage can be seen in the NTSB pics. So while that set up works great in normal ops, the roof panel is not designed to take extreme lateral loads and will fail along the edges of the roof beam, if that makes sense. Unfortunately have seen this failure before but not in this manner while in flight.

Too fuzzy to see clearly. Did it take part of the cabin roof / transmission deck with it?

Same on 206L

Never seen so much wear and tear on elastomerics and bearings, especially Lateral restraint.

I'm not an "engineer" in the true sense of the word but something doesn't sit right with me on Van Horn MR blades.

Nodal beam system on 206L series was designed and tuned for OEM Bell blades. Different harmonics, weight, aerodynamics etc.

The devil on my shoulder whispers "Boeing" with regards to certain FAA standards. If that makes sense?

I'm still curious why EASA won't certify VHA blades in EASA land?

By no means am I suggesting anything untoward with VHA blades.

Will be following this topic with interest.

The mast is obviously bent.

Yes. Its what the nodal system is bolted to via the roof beam situated on the underside of the roof/deck panel.

I would be, too, if I'd hit the water from that far up.

I think the ship structure behind lines up just right to make it look bent. Appears straight to me.

That looks like a catastrophic failure of the roof of the fuselage. Horrific.

My first thoughts, on seeing the video of the accident, was that one of the forward gearbox attachments had broken, allowing the gearbox to rotate backwards and for the blades to chop the tail. It now seems far worse!

ABC NEWS Video
 

https://cimg3.ibsrv.net/gimg/pprune....80abccf014.jpg

At first, I could see why dragon6172 felt the earlier photo posted here was deceptive and that the mast may not be bent (the remaining pitch control link seen in that photo has that effect). But looking at screen shots from the recovery footage, it sure looks like the mast is bent as The Sultan said. The bending seems to be mainly around and below the height of the swashplate. I am including a few of those shots, marking the direction to front of the fuselage for the portion ripped out of the cabin:

https://cimg1.ibsrv.net/gimg/pprune....3f17ce72d7.jpg
https://cimg2.ibsrv.net/gimg/pprune....e5506bf9ae.jpg
https://cimg3.ibsrv.net/gimg/pprune....13f6ee02c6.jpg

One of many questions now is whether both blades were already so fractured / delaminated in the air (and held 'straight' due to centripetal forces from the spinning rotor) or whether that fracturing was caused when they hit the water or during recovery?

I disagree: hold a straight edge against the image, and the mast above the swashplate is parallel to below the swashplate on both sides, in all photos shown here.


https://cimg7.ibsrv.net/gimg/pprune....e33bf7f96.jpeg

https://cimg0.ibsrv.net/gimg/pprune....157350f67.jpeg

So did the Rotor and trans separate from the frame or with part of the frame it was attached to?

Three of the four nodal beams are the newer type with a + shaped cross-section. The last one (aft) is the original type that has a rounded-corner square cross-section and is painted gray. Are they allowed to be mixed on the same aircraft?

What does the condition of the push pull tubes tell us?

One appears to be bent and the other is not but neither are twisted around the mast. What does that show us about the swashplate function?

Does that tell us the swash plate was working as advertised and the mast was turning the same rpm as the head and that at least part of the transmission was turning?


What say you Wrench,

Interesting to see the tips on one of the blades damaged. There was a bird strike incident in Australia with a similar outcome ( single main rotor blade contact, tail boom severed and full main rotor/transmission separation). Will be curious to see when they find the the tail boom to identify any witness marks.

I believe the blades broke on water impact or once underwater. They would have not been straight in the videos if broken. Plus have seen OEM blades break from water action once an aircraft rolled over after a successful auto into the water.

Don't quite follow what you're stating. From the pictures dont see much wrong with the nodal system except for one of arms appears distorted and a flexure appears to be broken which would be understandable in this sequence.

Nothing stands out. The missing main rotor pitch control link to the head is plausible. The swashplate drive link is intact, and all the big pieces are there. But since the servo web and servos remained with the fuselage I would have expected more damage to the bellcranks mounted on the front of the transmission. The yellow structure under the trans/nodal is the roof beam I mentioned earlier. Not seeing any smoking gun in those pics. To me, if it was a transmission seizure I would have expected to see the housing failed around the internal gear lines or at least the sw/plate drivelink sheared, but nothing. Regardless, still believe the loss of the MR drive/deck is a secondary result to some sort of failure with the tailboom group.

The four nodal beam focal links attach to the transmission via studs on the top case. A line between the center of these studs defines a plane normally perpendicular to the mast. In the pictures above where you can see these studs a line between them is not perpendicular to the mast.

Author: Associated Press

John: I may be wrong, but compare the orientation of the gearbox down low with the orientation of the mast up high. They seem completely different. It isn't as if there is a bevel gear between those parts. I have added some approximate straight lines through both to try to illustrate:

https://cimg0.ibsrv.net/gimg/pprune....e92ec1e70c.jpg

https://cimg2.ibsrv.net/gimg/pprune....1590ed99d0.jpg

I can certainly see how different people view this differently since I first thought bent, then straight, but now see it as bent again.

I don't think a bent mast necessarily gives any clues about the cause. Presumably massive loads on the system when it was pulled off the fuselage (for what ever reason), but as with what wrench1 says about the blades, any bent mast could have happened on striking the water (which isn't as 'soft' as we sometimes view it to be).

A few other observations:

(1) Does anyone see a pair of pitch links on the recovered rotor? I only see one.
(2) If a single pitch link failed and was ejected, how would the helicopter respond? Presumably quite unpredictably? (see this AH-1W case: https://nypost.com/2012/05/18/bird-s...investigators/ )
(3) Would a pitch link being ejected have been visible in any of the footage of the break-up sequence? John Kasuku (post #197) spotted two small items potentially parting early in the event, but realised they could simply be video artefacts.
(4) bryancobb at #225 thought he could see a different grey nodal beam. I suspect what he may be seeing is the same 'yellow' components as the others but blurred by the chain wire fence that the ABC News footage appears to have been taken through?
(5) Can anything be gleaned from the trajectory of the helicopter as seen in the footage of it passing behind the skyscraper? To me, it seemed to already be 'projectile motion' from early in the break-up sequence. At a stretch, that might mean collective had been lowered at around that point. I realise the video is through a 'fish eye' lens that would distort (curve) what may otherwise have been a straight and level flight path (at least initially).

If the heli has boosted pedals which it may have, you better not take your feet off them. The 206A had boosted pedals and was notorious for going full pedal if you took your feet off.

So in light of these latest photos, is it feasible that persistent vertical bounce (from the VH blades potentially) over time could weaken the whole roof structure enough for it to start to separate, causing the tail boom collapse and finally completely ripping the whole transmission and decking from the rest of the fuselage?

We know vibration causes cracks - anyone who has seen a station 290 crack on a Sea King will verify that - have they just been putting up with the vibrations not realising the potential for damage?

It's positive news that they have been able to recover so much of the aircraft

I don't think it will be too long before the authorities will be able to give further information on the likely cause of such a major destruction of such a well proven aircraft

Don't shoot me for mentioning fuel again, because I agree that this was much more violent than any sort of delayed auto or mistaken pedal input. Nevertheless, needing fuel was the last thing the pilot mentioned. So this is just to tidy up a loose end which nobody has mentioned...

If an electric fuel pump fails on a Jetranger then the effect is almost zero. If it fails on a Longranger then a flame-out will result at relatively low fuel states, but long before you would normally expect that to happen. The fuel guage will show you've got plenty (I think around 250lbs but I'm scratching old brain cells here) but it's actually unusable because it's lying in the mid tanks beneath the rear pax and it can no longer be transfered to the main tank and onward to the engine if there has been a fuel pump failure.

Thankfully, with the 290, it often told you it was cracked. A crew signed in with a "it flies much more smoothly now after the track and balance!" throw-away which I picked up on. Erm, wot track and balance....... :uhoh:

"Chief, just nip out and look at the 290 quickly will you?".

Upon his return ...... " OK, so that'll be U/S ufn for a frame repair then!". :ok:

But here, with this tragic accident, I think there are just so many variables right now. Made me think as I've been on one of those flights way back. It makes me shiver just thinking about what those poor people went through........ :sad:

We had one at Chivenor that had a confirmed crack which you could see clearly - but when the crane lifted the aircraft up by the rotor head to place it on the low loader, the crack opened up enough to fit your hand in!

helispotter yes, I see your point. I was looking at the mast above the MGB: nonetheless it is remarkable that the mast has remained not just in one piece but as relatively undamaged from the images that we have.

............. :uhoh: Must admit I didn't bother checking this (yet another) 290 victim after it's crane-off!

https://cimg0.ibsrv.net/gimg/pprune....fa109eb520.jpg

Anyway, enough "Frame 290" Thread Drift..........................

https://assets.publishing.service.go...pdf_500156.pdf

This accident report is for interest as there are some similarities.
Sadly there was nothing conclusive.
I had worked with the flight observer, nice guy.

I see on the NTSB web site that they have recovered the tail rotor system as well. No photos for us to spin new theories from, unless media got some. Recovery operations are finished. I expect we may not hear anything more from them until the preliminary report is out.