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Originally Posted by blakmax
(Post 10636937)
Most rotor blades are fabricated by adhesively bonding skins onto the spar and a honeycomb core. Adhesive design properties change significantly with temperature, the hotter the adhesive, the lower the strength and stiffness. If they get hot enough, the temperature may pass what is termed the Glass Transition Temperature where they change from a stiff glassy material to a soft, weak rubbery material. My guess is that the adhesive became so weak that the weight of the blades and the ash caused the blade to fail.
So sad. Blakmax |
No, the rotor blade is not of importance. As an Australian, given the number of (yet to be confirmed) Aussie casualties, my comment was not directed at the helicopter.
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It looks pretty clear to me that the blast of gases was so severe that it simply blew the helo backwards off it's pallet and the into-blast blades failed in flapping. This event wasn't just a pressure-pulse like an explosion, more like a sustained release of high pressure gas through a nozzle, a sustained super-gale-force blast lasting a few seconds. A wind strong enough to blow a helo off its pad would very likely snap the blades too.
Look how the gearbox air intake is packed with debris. If the machine had been parkd anything but nose-on to the crater it would probably have been cartwheeled across the area. |
During tours out there we used to walk past a massive rock split in two about the size of a small house. This was apparently ejected by an eruption early in the 1900's, when you stand next to it, you get a very vivvid idea of the forces at work.
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https://www.theguardian.com/world/20...tims-last-hope
New Zealand helicopter pilot describes horror of volcano rescue A commercial helicopter pilot who led a team that rescued 12 victims from the White Island volcano eruption has told how he believed he was their last hope of survival. “We found people dead, dying and alive but in various states of unconsciousness,” said Mark Law, a tour company boss who flew to the volcano and spent an hour on the ground even as a pillar of ash towered above them. Unsure whether emergency services would reach the island in New Zealand’s Bay of Plenty because of fears for their safety, they loaded the victims into the helicopters themselves and flew to the mainland... ...Law piloted one [AS350] Squirrel while his colleague Jason Hill flew the second with a fellow pilot, Tom Storey, as a passenger. Within 20 minutes they were directly over the island... ...Law and his colleagues loaded five people into each of their helicopters and another two into a third private machine that had followed them out... |
Originally Posted by visibility3miles
(Post 10637651)
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Brave men in very grim circumstances, doubt there was any training for a situation like this. |
For those of you that are having difficulty understanding the damage and destruction that can be caused, look up and try to understand "pyroclastic flow".
mickjoebill touched on it previously - A down draught effect from the initial ejection of earth as it fell back to ground? |
Near supersonic winds....lots of heat....plenty of rocks, molten lava, and other flying objects.....yes an interesting event.
In one of the links I posted earlier there is a photograph of a melted dashboard of a pick up truck.....14km's from Mt. St. Helen and Old Growth Douglas Fir Tree forests blown over even further than that....with even more scorched dead beyond that. |
Originally Posted by SASless
(Post 10638030)
Near supersonic winds....lots of heat....plenty of rocks, molten lava, and other flying objects.....yes an interesting event.
In one of the links I posted earlier there is a photograph of a melted dashboard of a pick up truck.....14km's from Mt. St. Helen and Old Growth Douglas Fir Tree forests blown over even further than that....with even more scorched dead beyond that. |
RNZN Seasprite left early this morning to retrieve remaining bodies - sounds like it may have been carrying members of SAS - NZ Herald now reporting six of the eight recovered.
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During tours out there we used to walk past a massive rock split in two about the size of a small house. https://cimg1.ibsrv.net/gimg/pprune....225f7ff936.jpg Correct in all details, except for molten lava, which forms an entirely different type of volcano. Incandescent rocks are possible, but its mostly superheated steam. A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava, tephra, pumice and ash. During the 1914 eruption, the western wall of the crater collapsed, allowing a lahar (a slurry of hot water and rock particles) to flow out of the crater and demolish the sulphur mining camp, killing ten people. It is this gap in the crater wall (obvious in the aerial photos) which allowed the eruption to blast sideways over the area where the tourists and the helicopter were. White Island, looking east into the breached crater: https://cimg4.ibsrv.net/gimg/pprune....9d9b464715.jpg |
Originally Posted by India Four Two
(Post 10638499)
During the 1914 eruption, the western wall of the crater collapsed, allowing a lahar (a slurry of hot water and rock particles) to flow out of the crater and demolish the sulphur mining camp, killing ten people. It is this gap in the crater wall (obvious in the aerial photos) which allowed the eruption to blast sideways over the area where the tourists and the helicopter were.
White Island, looking east into the breached crater: https://cimg4.ibsrv.net/gimg/pprune....9d9b464715.jpg I am curious that a helicopter has been used in the rescue mission, rather than a boat. No doubt the helicopter would reduce the time taken to move the bodies to an extraction point, compared to the peir point which is hundreds of meters further away. mjb |
Here is an update on the recovery of those that sadly died, as I mentioned before brave people doing this. https://www.bbc.com/news/world-asia-50753453 |
I am curious that a helicopter has been used in the rescue mission, rather than a boat. |
Originally Posted by RVDT
(Post 10638682)
if you are referring to the B2 it was there already before the eruption. I’m curious as to the risk analysis of boats v helicopters. mjb |
mjb,
Having been there, I would say that using a helicopter is much less risky, assuming you don't shut down. It would be much easier to make a quick getaway. Still not without risk though. If using a boat, he pier is about 800 metres from the crater and it would be fairly slow going, even before the recent eruption and ash fall. |
I've had a bit of experience flying volcanologists into active volcanoes (including Turvurvur which is the volcano in this YouTube video). They are the type of job you are never comfortable about nor can be complacent about. I was always relieved when the job was done. I've seen rocks as large as cars being shot out of volcanoes. And the sonic boom when they start misbehaving certainly gets your attention. They most certainly are not a place you want to find yourself only wearing shorts, T-shirt and a tin hat and respirator.
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It would have made the cabins rattle in that container ship.
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The reported "retrieval" crew kind of makes me wonder what they were thinking...reported as NZ SAS E-squadron, ie specialist EOD crew. Why on earth would you put guys/gals trained to that degree up for a task like this?
Sure they would be trained to work in an NBC environment with protective gear but so would lots of other folks without quite as a specialized background that could take years to re-coup if things had gone boom when on the island. |
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