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.