Landing under HT cables
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The point of my video was to show even well trained and skilled pilots who are aware of their surroundings make mistakes. In the EMS incident he got away with it but it just shows how quickly it can go wrong.
Peter - I do agree wholeheartedly with your comments.
There are 2 main problems with going under HT wires - the first is the risk of disorientation if you look up to check your clearances, this should have been established before you venture under them by comparing the height of the cables with the rad alt reading (if you have one, if not you are just cuffing it).
The second problem is that of arcing - when I told a relative who works for National Grid, he was horrified that we taught people to hover taxi under HT cables. The guys that work on them (not in helicopters) have to comply with stringent safety precautions - 400KVA is a sh*tload of power and, whilst you might hope that any arcing would be routed around the helicopter by the bonding of components, it wouldn't take much to get that wrong.
Pick another LS!
The thread running on 'Helicopter down near Tring' seems to indicate yet another unplanned coming together of HT cables and helicopter!
There are 2 main problems with going under HT wires - the first is the risk of disorientation if you look up to check your clearances, this should have been established before you venture under them by comparing the height of the cables with the rad alt reading (if you have one, if not you are just cuffing it).
The second problem is that of arcing - when I told a relative who works for National Grid, he was horrified that we taught people to hover taxi under HT cables. The guys that work on them (not in helicopters) have to comply with stringent safety precautions - 400KVA is a sh*tload of power and, whilst you might hope that any arcing would be routed around the helicopter by the bonding of components, it wouldn't take much to get that wrong.
Pick another LS!
The thread running on 'Helicopter down near Tring' seems to indicate yet another unplanned coming together of HT cables and helicopter!
Hence wasaloadie's comments about 12 ft above. 7 ft below and 15 ft lateral clearances.
We used to use 50 ft on the radalt as a guide, if you could line up the bottom two strands and have 50 ft on the radalt, you should be able to hovertaxy under the wires at 10 ft with the appropriate safety clearance between the rotors and the cables.
We used to use 50 ft on the radalt as a guide, if you could line up the bottom two strands and have 50 ft on the radalt, you should be able to hovertaxy under the wires at 10 ft with the appropriate safety clearance between the rotors and the cables.
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crab
I don't think you will get any arcing with the heli in the air, it has to be grounded. A rotor blade would have to contact at least two wires at the same time in order to do that.
Birds land on them with no bother after all.
The second problem is that of arcing
Birds land on them with no bother after all.
Last edited by chopjock; 10th Sep 2015 at 18:22.
Purveyor of Egg Liqueur to Lucifer
Chopjock;
I don't think you will get any arcing with the heli in the air, it has to be grounded. A rotor blade would have to contact at least two wires at the same time in order to do that.
Birds land on them with no bother after all.
I don't think you will get any arcing with the heli in the air, it has to be grounded. A rotor blade would have to contact at least two wires at the same time in order to do that.
Birds land on them with no bother after all.
As for them pesky birds;
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Overhead line inspections at least in the UK never involve flying under the lines, alongside, at least a couple of rotor diameters away from the conductor is close enough to for the thermal imaging camera to identify hotspots.
Chopjock - back to basics school for you I think.
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back to basics school for you I think.
Also the first video shows a static discharge where the PD of the floating static on the heli is matched with the line, that is all. It is floating, only static, as in not earthed or connected to another phase. Notice no harmful effects to the helicopter.
Your post is totally bullsh......t
if you fly below an HT cable you'll reduce the distance between the cable and the ground. In case of an 400kv line the allowed distance is about 4 metres.
If the cables hanging quite low p.ex. In the middle of the field you really have an arcing problem, even when the heli don't touches the ground!
I'am line cowboy since 3years and belive me, never fly below HT when the distance between cable and ground is to low!
if you fly below an HT cable you'll reduce the distance between the cable and the ground. In case of an 400kv line the allowed distance is about 4 metres.
If the cables hanging quite low p.ex. In the middle of the field you really have an arcing problem, even when the heli don't touches the ground!
I'am line cowboy since 3years and belive me, never fly below HT when the distance between cable and ground is to low!
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What Bellrider says. And I believe the primary reason for bonding the helicopter and, more importantly, the crew's conductive suits onto the line is to eliminate the effects of the extremely high voltage gradient in the electric field strength that exists in very close proximity to the line. This gradient reaches thousands of volts/meter. It's not very survivable to have a thousand volt potential between your head and your feet. Birds get away with it because they are so small. The suit makes the voltage the same all over the body, thereby eliminating that problem. I have read that having a small "leak" or tear in a conductive suit leads to some rather unpleasant sensations 
And to Bellrider's original point, the guys who work on these things while they are energized have to VERY carefully respect stand-off distances to tower components. Closing the gap between a tower component and the line below that afforded by the insulators lead to Very Bad Things.
And to Bellrider's original point, the guys who work on these things while they are energized have to VERY carefully respect stand-off distances to tower components. Closing the gap between a tower component and the line below that afforded by the insulators lead to Very Bad Things.
Flying underneath powerlines is sometimes part of the buiseness - even so, avoided, if there is an suitable alternative.
But itīs not a big deal, if you are propperly trained.
But itīs not a big deal, if you are propperly trained.
High voltage can jump 1 cm per 10.000 Volts, this is due to the conductivity of normal air. 400 KV therefore can jump 40 cm.
To add safety to this the risk area in sweden is a radius of 2.5m in air if I remember it right.
I've done a lot of flying underneath powerlines, both crossing and following under for some hundred meters. My total time underneath powerlines is measured in hours, not seconds. Never hade any problem, despite including rainy days, snowy/dusty conditions etc.
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There are 20,000 miles of powerline here in Quebec alone, not including the rest of Canada. That's just the 735 KV AC lines and one 450 KV DC line. Flying beside, on top or underneath a powerline is part of our everyday work. Most of the time being underneath the line (conductors) is the only place where you can land, work and park.
In my 36 years of flying and a lot of them working the lines I have never heard of a Helicopter being zapped by or electricity jumping from the conductors to a helicopter no matter what the weather was.
Bell 205 moving repair crews around the job.
JD
In my 36 years of flying and a lot of them working the lines I have never heard of a Helicopter being zapped by or electricity jumping from the conductors to a helicopter no matter what the weather was.
Bell 205 moving repair crews around the job.
JD
The stories from all guys writing here how many hours they have underneeth HT's are not interresting! I can altought tell you that i've flown 5t hours without having Vortex or Lte! But this is not the fact. Important is to know what is to do not to get into that situation.
The topic was :what is dangerous when flying in wire environment .....
Every professionell ht technican will tell you the things i told you before......
So good luck to all guys thinking today it works so it will altought works tomorrow.....
The topic was :what is dangerous when flying in wire environment .....
Every professionell ht technican will tell you the things i told you before......
So good luck to all guys thinking today it works so it will altought works tomorrow.....
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You do not need to fly near high voltage lines to get electricity to the cargo hook. I've seen soldiers knocked completely off the back of 2.5T trucks when trying to hook them up to Chinooks. I've done many hours of slingloads in BH206 models, and they all create static electricity. The ground guys are taught how to dissipate the current before actually connecting the sling line to the hook.
Lots of old wives' tales on this thread, and apparently a lot of old wives, too.
Lots of old wives' tales on this thread, and apparently a lot of old wives, too.
