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Post by Deleted on Nov 24, 2011 10:57:48 GMT 12
I would have thought the a cable wouldn't bring a helicopter down like that. I mean it would have done damage, but I probably wouldn't have said it to cause it to crash. I thought the rotor blades would have just cut the cable in half, must have been a bloody strong cable? I have seen a video where a tail rotor has cut through a powerline without affecting it, although he did land due to precautionary measures i would say. Here is the video
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Post by Darren Masters on Nov 24, 2011 11:09:46 GMT 12
Crash a helicopter and await this infront of you: That's just a small portion of the 'circus' outside the hangar. Guess we know what will be on Campbell Live tonight
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Post by Dave Homewood on Nov 24, 2011 11:23:26 GMT 12
Powerlines are merely made from copper, not steel like these high tension cables.
As I understand it, a slight damage to a rotor blade can cause an imbalance, and the vibration from that can destroy a helicopter in seconds. It's called ground resonance i believe. That is what nearly destroyed one of the RNZAF's Seasprites.
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Post by baronbeeza on Nov 24, 2011 11:36:45 GMT 12
That video of the Ambulance fight is incredible. That seemed to be one hell of a risk to be taking.
I thought it was a main rotor blade that struck the cable a glancing blow from underneath. I am not a helicopter man but would possibly have acted against the hinge action of the blade and could not have easily sliced a section off. In the Akl mishap it was sudden imbalance and consequent shaking that brought everything to a sudden halt. The engine would have been winding down from 30,000 rpm or whatever they spin at. All load had been removed from it as would have been the fuel supply.
A very dramatic crash and I sure we will be seeing that over again in the coming years. I could not make out what cable he actually clipped, - any pointers ?
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Post by Bruce on Nov 24, 2011 11:46:49 GMT 12
Problem with a cable strike is that it upsets the tracking of the blades - in this instance a rotor blade severed the tailboom very early in the sequence, and generally things go downhill from there real quick! the damage to the blade from the cable mightnt have been much, but by the time its been through the tailboom, well......
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Post by lumpy on Nov 24, 2011 11:47:58 GMT 12
Powerlines are merely made from copper, not steel like these high tension cables. As I understand it, a slight damage to a rotor blade can cause an imbalance, and the vibration from that can destroy a helicopter in seconds. It's called ground resonance i believe. That is what nearly destroyed one of the RNZAF's Seasprites. Ground resonance is a little different . Its kind of a harmonising of the normal vibrations , as the aircraft touches the ground ( taking off again is the way to stop it ) . The guy in this video was very lucky , you can hear a nasty noise after the power line contact , proving damage was done . I have seen an aborted take off caused by an excessive vibration that was the result of a supermarket plastic bag wrapped around a rotor blade ( and how little do those things weigh ) ?
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Post by scrooge on Nov 24, 2011 11:53:54 GMT 12
I think one of the guy wires for the tower from watching that video, rather than the lifting wire. Will see what comes out of the investigation.
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Post by Darren Masters on Nov 24, 2011 11:56:44 GMT 12
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Post by hairy on Nov 24, 2011 13:08:50 GMT 12
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Post by baz62 on Nov 24, 2011 13:24:59 GMT 12
Yes it sounds awful doesn't it?
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Post by Deleted on Nov 24, 2011 13:32:56 GMT 12
I guess I was wrong haha
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Post by davel on Nov 24, 2011 13:38:47 GMT 12
Tail boom separation is not uncommon when main rotor blades come into contact with something. Here is another much more horrific example:
Sometimes cargo hooks fail to release on their own, they require a bit of weight on the hook to get it to open, looks like what they were trying to achieve here.
Seconds after it all comes to rest you can see the ground crewman, the same one that had to dive out of the way as it all went pear shaped above him, climb up and shut the engine off. Good on him for keeping calm and doing what he is trained to do!
Ground resonance is an issue of main rotor balance. It can only occur on helicopters with fully articulated rotor systems (flap, feather and lead lag) any number of things can cause it, faulty lead lag dampers, faulty oleos, heavy landing etc. It is only an issue when the helicopter is in contact with the ground, hence the name. Simple solution if you get ground resonance is to lift off again, problem goes away. A main rotor balde contacting something is going to cause a MASSIVE imbalance as we see here.
Heres a video of a US Chinook ground resonance demo:
Feel really sorry for Greg, this will probably be the most widely viewed helicopter crash ever. Made the news here in Canada..
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Post by Calum on Nov 24, 2011 13:42:13 GMT 12
Yes it sounds awful doesn't it? I guess thats what happens when it's no longer connected to the Main rotor gearbox I wonder if the rescuers shut it down or it just ran out of fuel.
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Post by crewdog on Nov 24, 2011 14:18:59 GMT 12
Feel really sorry for Greg
Well said davel and your correct it will be a well viewed piece of action worldwide. I guess anyone who has ever walked past a helicopter at an airshow will now have an opion about this but I gaurantee the most inaccurate will come from the people in the photos Darren posted!
I feel for Greg and the staff at Helisika right now but as the saying goes "todays news is tomorrows fish and chip paper" and the media,like a rash between your legs WILL eventually go away and leave you alone.
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Post by Darren Masters on Nov 24, 2011 15:18:52 GMT 12
Feel really sorry for Greg Well said davel and your correct it will be a well viewed piece of action worldwide. I guess anyone who has ever walked past a helicopter at an airshow will now have an opion about this but I gaurantee the most inaccurate will come from the people in the photos Darren posted! I feel for Greg and the staff at Helisika right now but as the saying goes "todays news is tomorrows fish and chip paper" and the media,like a rash between your legs WILL eventually go away and leave you alone. Very well said and I too feel sorry for Greg and his family. It still does not totally sink in just how lucky he is to be with them at this time...Will be interesting to see what they make of it tonight both on 3 News and Campbell Live...
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Post by bazzaboeing on Nov 24, 2011 15:43:20 GMT 12
Not sure but looking at the video footage from Campbell Live the photographer must have had two cameras set up for the shot. He can be seen running from right to left just before the Helicopter hits the cable and then he is seen running to the chopper to help the pilot just after that. I doubt that he would have got any shots from the camera he shifted as he did not have enough time to set it up, or was there another cameraman?
Looking at the video I do not think that it will take the Air Accident Inspector long to come to a conclusion as to why/how this accident happened. Could have been a lot worse and this may mean serious restrictions in operating Helicopters in built up areas and how close people are allowed to it in it's operations.
Cheers Bazza
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Post by davel on Nov 24, 2011 15:52:55 GMT 12
Why will there be any additional restrictions? An operation like this requires a congested area plan. This includes things like crowd control, emergency plan etc. all this was in place and this is why no one was injured..
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Post by Darren Masters on Nov 24, 2011 15:54:22 GMT 12
From a statement from the camera guy, yes, he did have two cameras.
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Post by Darren Masters on Nov 24, 2011 15:57:02 GMT 12
And totally agree with davel. Can you imagine there had been no crowd control? There would have been many people killed I'm sure of it. I don't think anything was wrong until someone yanked on the cable...
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Post by Darren Masters on Nov 24, 2011 17:08:00 GMT 12
Well the 3 News piece was relatively painless...
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