Originally Posted by bryancobb (Post 11866741)

I was just doing my unscientific dive into the falling rotor system. After zooming and watching the few seconds as the rotor was falling, It appears there was no "wobbling" as it was spinning, the blades appeared to be the same length, and they appeared to not be bent. The stable nature of the spinning rotor seems to indicate that the unsymmetrical mass at the gearbox-end of the mast IS NOT SPINNING. I would have a hard time believing the gearbox seized or locked-up. I'd appreciate others' thoughts.
https://cimg0.ibsrv.net/gimg/pprune....125eebde45.jpg

Originally Posted by The Sultan (Post 11866372)

I once witnessed (from extremely close range) an AH-1W running on the ground at 100% rpm release an internal main rotor blade weight due to a decade old manufacturing error. When the weight departed it:

1. Blew the end of the blade off,
2. Snapped the main transmission horizontally in half,
3. As the rotor/top case exited the still attached controls put in full pitch,
4. The aircraft was lifted 6’ or so by the control tubes which then failed dropping the fuselage back to the ground,
5. The now unattached rotor climbed 80’ before loosing energy and crashing down in front of the airframe.

The magnitude of the unbalance was so large the xmsn was snapped within one revolution of the rotor so no large 1/rev forces were transmitted to the fuselage. The only fuselage damage was to the cross tubes on one side. The pilot commented that he heard a bang, the aircraft smoothly lifted before falling back to the ground. The airframe was refurbished and returned to service.

if the weight had been less and not immediately snapped the xmsn case, the excessive 1/rev would probably have broken the pilot’s neck and damaged at least the tailboom.

So back to this thread. It is plausible a failure in a blade caused excessive 1/rev which buckled the tailboom and put in full tail rotor pitch through the still connected controls tubes causing the observed yaw. Then a combination of 1/rev loads and aero forces caused the rotor/xmsn/nodal beam to depart with the rotor appearing to fly away intact.

Won’t know until we see both blades.

Originally Posted by Dave 92 LSC (Post 11866831)

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

Originally Posted by TwinHueyMan (Post 11866160)

Scary thing is, if it was the Van Horn bounce, putting the collective down only makes things worse. The info letter put out about it less than a month ago says the harmonic is the same natural frequency as the tailboom.

Van Horn 206L MRB IL

Pictures I've seen of a suspected VH bounce that got on the ground has severe damage in the same area of the tailboom that was the break point on the New York machine.

Originally Posted by snotcicles (Post 11866843)

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.

Originally Posted by bryancobb (Post 11866783)

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?

Originally Posted by Hedge36 (Post 11866838)

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

Image of the assembly included.

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

Originally Posted by snotcicles (Post 11866843)

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.

Originally Posted by albatross (Post 11866877)

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

Originally Posted by The Sultan (Post 11866887)

The mast is obviously bent.

Originally Posted by The Sultan (Post 11866887)

The mast is obviously bent.