There is a lot going on in that video that I would need additional information to make an accurate assessment of what exactly happened.
I tried to find the accident report to no avail.
Early in my naval career, I was involved with three accident investigations so I never rush to judgment...what often seems quite clear early in the investigation can turn out to be a non-causal factor in the accident. I have over 4000 flight hours in over thirty aircraft and helo type model series.
A few observations. Since it is difficult to see the landing site, I cannot say for sure if he was trying to land on a raised platform...many flight centers that operate fixed, skidded helicopters (including med-flights, police) land on raised, wheeled platforms to ease the task of getting the helo in the hangar or in a designated parking area. It really isn't that hard.
It appears he had a very shaky landing. I don't think it was so bad that it would have caused what is called, "ground resonance"...a phenomenon that can literally cause a helo to shake itself apart on the ground
It also appears that the helo momentarily comes to rest at a tilt. This could have been caused by siding off the raised platform or a failed skid. Hard to tell since he bounced to port quite a bit on landing. Most raised platforms are fairly narrow.
In the video after the helo rolls, you can see the left skid and it looks fine. But, again, looks can be very deceiving.
What happen after he momentarily comes to rest with a tilt is very odd. Bear with me.
When the rotor of a helicopter turns it produces reaction torque which tends to make the craft spin also on vertical take-off. On most helicopters a small rotor near the tail compensates for this torque. When a pilot lifts the "collective" control, power to the main rotor increases and all main rotor blades increase pitch collectively...to counter the reaction torque, the pitch on the tail rotor must also be increased or the helicopter will spin.
I can think of a few things that would have caused the helo in the video to spin so severely:
- Loss of tail rotor power. This is every helo pilots worse nightmare. If the drive shaft to the tail rotor (TR) should fail in any manner, or the TR transmission fail, the helo will spin and bad thing happen.
- Loss of TR control. Control of the TR is managed by what fixed wing folks call rudder pedals. There is a host of control mechanisms, hydraulic acuators, etc. between the rudder pedal and the TR. Failure of any of them means the pilot no longer can input to the TR. Depending on when and at what power setting this failure occurs, the helo can spin.
- Loss of TR authority. It is possible to exceed the limit of the TRs ability to counter the torque reaction. There is a bunch of ways to do this but the video highlights two potential loss of TR authority.
1. If a skid gets stuck under something on the ground, it is possible that the pilot will pull more than normal power if he is not aware of the stuck skid. At very high power settings it is possible that a sudden release of the skid can caused the helo to exceed the TRs design control parameters momentarily and the helo will spin. This happen to me one nigh on the back of a frigate, but that is another story
2. With one skid hooked to the ground with a pivot point, is it possible that the helo will spin around that pivot point as the pilot increases power.
Sorry for the long ramble...