Well spotted JD.
The object in the RHS Crewmen’s window (looks like a helmet, but doesn’t move), appears to be fixed in the vertical position. The amazing thing is that it doesn’t appear to move throughout the video – even after the impact. It appears totally transfixed to the vertical position for whatever reason with no evidence of any sort of a clearing scan whatsoever as Crab said. – very strange. Even after the impact and the camera resumes the aircraft in the field of view during its climb out, the “helmet” appears to be fixed in the vertical position. This would seem very strange given that most people instinctively move there eyes to observe any sudden loud noise which was clearly evident at and post impact. Not seen in this case.
For bellfest : Nr 258rpm – but probably a little less on this occasion due to the sudden increase in rotor drag due to the shattered rotor tip/s
(I know,….. the FCU would have maintained 100%Nr….just couldn't resist it)
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For BlackHawk9: Yes, had one blade flex down and take a clip out of the T/R Intermediate gearbox fairing once…perhaps that's why Sikorsky designed it to be sacrificial??
No damage to the tip cap on that occasion but a different story for the IGB fairing. And many others that we are all aware of ..thank heavens they were all in B’Hawks!
Perhaps the reason Bell has the requirement for a “Sudden Stoppage” inspection is that like the CH47 and many other blades of that generation (AS322, AH1, etc), they all had full length spars running right to the tip. With the Span tip weight pockets located in and around the spars ie the main blade structure went right to the tip. There were no sacrificial components designed to dissipate energy in event of sudden impacts. I think you will find the B212 will be not unlike the B204/205 with a “D” spar right to the tip. The Span Static weight pockets will be located immediately behind the rotor tie down eyelet. You will see an example of this in the link posted earlier and below of the UH1 tip. Go down to "Static/OEM Blade Adjustments" to see a diagram and pics of various tip caps and rotor structures including UH1/Ch47/As322/others.
https://www.rwas.com.au/blade-balancing/
As you would know (and many others who have the pleasure of some UH1 experience), who hasn’t experienced the “thwack-thwack” as the tips gently hit the soft green mangrove leaves along Shoalwater Ck while your crewman tries to retrieve some crab dilly pots out of the water with a fire rake?
No harm with soft impacts...rotor blades can be quite surprisingly robust and damage tolerant.
If you do have a significant blade strike (i.e. take the blade end cap off) in these earlier full length structures, the energy from the impact will travel down the load path through the Transmission and drive train components. The sudden impact forces has the potential to cause stress damage to various components in along this drive train.
I’m sure you will be familiar with these in any case BlackHawk9. But others may not.
The B412 for example, does not have its spar (fibreglass) run all the way to the tip. It's Tip cap however is only relatively small and not sacrificial. Its big disadvantage is that the tip cap is a bonded fairing and houses its Static Span weights in the form of lead pellets or beads. They are inserted in the top through a very small flush mounted Allen bolt. The lead pellets then get deformed under centrifugal force to solid mass. The only way you can adjust these is to physically debond the tip cap. It is subject to a tip strike, it is highly likely to loose all the Static Span moment arm balance weight and set up quite a significant lateral…not a very clever design.
Other examples of sacrificial design features for rotor blade strikes are seen on the Bk117. The vertical fins have sacrificial segments designed to shear away without causing structural damage to the main fin and leaving still an aerodynamic surface. This enables a pilot to recover the machine back to maintenance rather than leaving it parked up in a paddock. A clever design feature to overcome a different design flaw which was later rectified on the 145 models.
See link below – go down to a couple of paras where it describes Blade Flex.
https://www.rwas.com.au/tool-description/
Gordy: – Totally agree with ya….