Corona discharge revisited....
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Nick thank you for your answer, i ll follow your postings, but i dont have your skills, so, i m scared i ll be ridiculous...
charge faster than discharge ? i dont know a "slow" discharge or a mean to slow a discharge ... unless the air acts like a capacitor or a cell... well, i leave the debate, i m not enough skilled,
i just learn this corona effect was visible and neat... and wanted to know how it apprears, and what are the pb generated by that,
dont laugh please, i want to build a chopper... sh..t i lost my credibility !
cheers
charge faster than discharge ? i dont know a "slow" discharge or a mean to slow a discharge ... unless the air acts like a capacitor or a cell... well, i leave the debate, i m not enough skilled,
i just learn this corona effect was visible and neat... and wanted to know how it apprears, and what are the pb generated by that,
dont laugh please, i want to build a chopper... sh..t i lost my credibility !
cheers
Join Date: Apr 2003
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zeeoo,
Do not fear - asking questions and making opinions for the discussions is what pprune is all about. Jump in, as you have, and fight for your beliefs and understanding!
I agree, the static discharge is as fast as the speed of light, literally.
I do not doubt what Lu has said about coronas caused by static electricity, I just know it is not common, and not the cause of the blades lighting up on landing at LZ's.
Do not fear - asking questions and making opinions for the discussions is what pprune is all about. Jump in, as you have, and fight for your beliefs and understanding!
I agree, the static discharge is as fast as the speed of light, literally.
I do not doubt what Lu has said about coronas caused by static electricity, I just know it is not common, and not the cause of the blades lighting up on landing at LZ's.
That's Life!!
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Nick
I wasn't actually agreeing with Lu on the origin of the discharge.
We certainly never experienced this when landing on a concrete pad at base, only in the desert or beach areas; which, I think will confirm, that IT IS caused by collision of dust/sand particles with a moving rotor, both main and tail.
It was certainly visible without the use of NVGs.
I wasn't actually agreeing with Lu on the origin of the discharge.
We certainly never experienced this when landing on a concrete pad at base, only in the desert or beach areas; which, I think will confirm, that IT IS caused by collision of dust/sand particles with a moving rotor, both main and tail.
It was certainly visible without the use of NVGs.
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i remember my father telling me about a trip he did taking supplies to the island of malta during the second world war.
he was flying a sunderland flying boat and on the way home to england over the bay of biscay they flew through an electrical storm and the aircraft experienced st elmo's fire and glowed from wing tip to wing tip nose to tail.
the tail gunners weapons and the top gunners weapons discharged electricity to the atmosphere. the phenomena lasted for quite some time.
he was flying a sunderland flying boat and on the way home to england over the bay of biscay they flew through an electrical storm and the aircraft experienced st elmo's fire and glowed from wing tip to wing tip nose to tail.
the tail gunners weapons and the top gunners weapons discharged electricity to the atmosphere. the phenomena lasted for quite some time.
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St. Elmo's Fire
St. Elmo's fire is always associated with nearby convective activity, because it is the aircraft (or ship) acting like one of those objects the magician puts near a Van De Graf generator. The charge is already in the air, and the aircraft picks it up.
http://geoffreyegel.tripod.com/vande.htm
I was flying a light twin near some pretty cumulus that hung like Chinese lanterns along the Atlantic coast of North Carolina. I was maybe 1/4 mile from the tops at their level, and weaving among them, and they were softly glowing from the internal lightning. No cloud to cloud and no clound to ground, just the soft popping internal lights that made them glow yellow-orange. It was just after dusk, and looked great.
The wings began to pick up a green and blue glow that danced and shifted in soft billows, as if it were silk scarves moving in a gentle breeze. The light was not very bright, but very noticible, and it was facinating! It disappeared when I left the clouds behind. I am sure it would have been noticible from a distance.
http://geoffreyegel.tripod.com/vande.htm
I was flying a light twin near some pretty cumulus that hung like Chinese lanterns along the Atlantic coast of North Carolina. I was maybe 1/4 mile from the tops at their level, and weaving among them, and they were softly glowing from the internal lightning. No cloud to cloud and no clound to ground, just the soft popping internal lights that made them glow yellow-orange. It was just after dusk, and looked great.
The wings began to pick up a green and blue glow that danced and shifted in soft billows, as if it were silk scarves moving in a gentle breeze. The light was not very bright, but very noticible, and it was facinating! It disappeared when I left the clouds behind. I am sure it would have been noticible from a distance.
Kopp-Etchells effect
Quite amazing phenomena and some superb photography.
In memory of the late Lu Zuckerman who swore he had seen this with his own eyes!
The Kopp-Etchells Effect
In memory of the late Lu Zuckerman who swore he had seen this with his own eyes!
The Kopp-Etchells Effect
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Actually, those pictures prove that Lu was mistaken when he said that he saw the aircraft in cruise, miles away, with the strange lights. He said it was coronal discharge, and several of us said that it was the effect of silicate sand and dust, disturbed by the blades. The pictures show it starting when the blades are immersed in dust, and stopping when they leave the could.
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Kopp-Etchells Effect
You have my support in suggesting this name should be given to what is a natural effect that has caused such a large amount of interest, I am certain no one would disagree with the ability to name this so.
Equally, I am certain the familys of the two Brave individuals who have left their mark in passing from us in this manner, so unbefitting in our lifestyle, will also feel honoured!!
On a different note, those photographs are superb, thank you for sharing them and the well explained background to us all.
My regards
PeterR-B
Vfrpilotpb
Equally, I am certain the familys of the two Brave individuals who have left their mark in passing from us in this manner, so unbefitting in our lifestyle, will also feel honoured!!
On a different note, those photographs are superb, thank you for sharing them and the well explained background to us all.
My regards
PeterR-B
Vfrpilotpb
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The Kopp-Etchells Effect
Benjamin Kopp, a US Army Ranger, and Joseph Etchells, a British soldier, were killed in combat in Sangin, Afghanistan. In 2009, war correspondent Michael Yon gave the physics of helicopter halos its name to honor the two soldiers who were killed in combat in July of that year.
Documenting helicopters descending in Afghanistan, he took dozens of photos showing glowing halos imposed on the helicopter’s blades like spiral galaxies. Nobody knew what the halos were. The helicopter pilots had their own theories. Yon describes speaking to one pilot who said the halos were “a result of static electricity created by friction as materials of dissimilar material strike against each other.” On forums and message boards there were other ideas. Some believed that the extreme speed of the helicopter blades was pushing dust out of the way so fast that it burned up like meteors in the atmosphere.
Both theories have problems. A static discharge looks nothing like a shower of sparks and blades going fast enough to heat particles in the air around them would heat up themselves. Without any published research to go on, the most likely theory is one that matches the physical phenomenon and explains others.
When a helicopter descends into a sandy environment, the enormous downward thrust from the blades inevitably kicks up a cloud of sand. Cutting through the sand and dust, the blades smash into millions of these tiny particles, each sandblasting metal from the blade. Most of the time the only visible consequence to the helicopter is pitting on the blades, with enough damage warranting replacement. Every so often, however, the metal blasted from the blades produces a miniature meteor shower.
To prevent early degradation, most helicopter blades are coated with an abrasion strip. This strip, typically made of a metal like titanium or nickel, prevents the leading edge of the blade from being worn down too quickly by the various particulate hazards of the atmosphere. This abrasion strip can handle a lot of wear and tear, but the desert is a harsh environment. Sand is harder than the titanium or nickel that makes up the abrasion strip, so when a helicopter’s blades begin cutting through a cloud of sand, the particles hit the blades and send bits of metal flying into the air.
It turns out that the metals comprising the abrasion strips on helicopter blades can be pyrophoric—they can spontaneously ignite in air. But of course this doesn’t happen in normal circumstances; we don’t see bricks of nickel bursting into flames. Rather, the spinning blades of the helicopter generate a cloud of metal particles. Once in that form, the metal particles can ignite and light up. Like sawdust or flour, finely powered metal can and does explode.
This abrasion strip can handle a lot of wear and tear, but the desert is a harsh environment. Sand is harder than the titanium and nickel that make up the abrasion strip, so when the blades begin cutting through a cloud of sand, the particles hit the blades and send bits of metal flying into the air.
Working in tandem with the courageous photographer who actually took these amazing photos–Michael Yon, Kyle Hill was also fortunate enough to take some of his own:
The Beautiful Science of Helicopter Halos | Overthinking It, Scientific American Blog Network
Mystery in Motion, Beauty in Battle - Facts So Romantic - Nautilus
The Kopp-Etchells Effect Explained | Science-Based Life
Documenting helicopters descending in Afghanistan, he took dozens of photos showing glowing halos imposed on the helicopter’s blades like spiral galaxies. Nobody knew what the halos were. The helicopter pilots had their own theories. Yon describes speaking to one pilot who said the halos were “a result of static electricity created by friction as materials of dissimilar material strike against each other.” On forums and message boards there were other ideas. Some believed that the extreme speed of the helicopter blades was pushing dust out of the way so fast that it burned up like meteors in the atmosphere.
Both theories have problems. A static discharge looks nothing like a shower of sparks and blades going fast enough to heat particles in the air around them would heat up themselves. Without any published research to go on, the most likely theory is one that matches the physical phenomenon and explains others.
When a helicopter descends into a sandy environment, the enormous downward thrust from the blades inevitably kicks up a cloud of sand. Cutting through the sand and dust, the blades smash into millions of these tiny particles, each sandblasting metal from the blade. Most of the time the only visible consequence to the helicopter is pitting on the blades, with enough damage warranting replacement. Every so often, however, the metal blasted from the blades produces a miniature meteor shower.
To prevent early degradation, most helicopter blades are coated with an abrasion strip. This strip, typically made of a metal like titanium or nickel, prevents the leading edge of the blade from being worn down too quickly by the various particulate hazards of the atmosphere. This abrasion strip can handle a lot of wear and tear, but the desert is a harsh environment. Sand is harder than the titanium or nickel that makes up the abrasion strip, so when a helicopter’s blades begin cutting through a cloud of sand, the particles hit the blades and send bits of metal flying into the air.
It turns out that the metals comprising the abrasion strips on helicopter blades can be pyrophoric—they can spontaneously ignite in air. But of course this doesn’t happen in normal circumstances; we don’t see bricks of nickel bursting into flames. Rather, the spinning blades of the helicopter generate a cloud of metal particles. Once in that form, the metal particles can ignite and light up. Like sawdust or flour, finely powered metal can and does explode.
This abrasion strip can handle a lot of wear and tear, but the desert is a harsh environment. Sand is harder than the titanium and nickel that make up the abrasion strip, so when the blades begin cutting through a cloud of sand, the particles hit the blades and send bits of metal flying into the air.
Working in tandem with the courageous photographer who actually took these amazing photos–Michael Yon, Kyle Hill was also fortunate enough to take some of his own:
The Beautiful Science of Helicopter Halos | Overthinking It, Scientific American Blog Network
Mystery in Motion, Beauty in Battle - Facts So Romantic - Nautilus
The Kopp-Etchells Effect Explained | Science-Based Life
I completely reject the notion of someone naming a "helicopter phenomena" after a couple of soldiers they knew, regardless of the respect those soldiers are undoubtably due.
Especially given that the "phenomena" is not even a "phenomena" but a well known and very common outcome. Just because it was the first time a few people had experienced and seen it and wondered about it does not make this some newly discovered and mysterious phenomena.
Creating a bogus explanation with scientific sounding legitimacy does not create a "phenomena" out of an everyday event.
I simply cannot believe the power of the Internet to exteapolate this observation of a well known and occurance into a whole new scientific phenomena involving metal particle fields and now the requirement to invent a special name.
It is all quite unbelievable really.
I shall call this Internet phenomena the "Lu Zuckermann Effect".
And Lu, we do miss your posts here mate - the prune is just not the same these past years. RIP mate.
Especially given that the "phenomena" is not even a "phenomena" but a well known and very common outcome. Just because it was the first time a few people had experienced and seen it and wondered about it does not make this some newly discovered and mysterious phenomena.
Creating a bogus explanation with scientific sounding legitimacy does not create a "phenomena" out of an everyday event.
I simply cannot believe the power of the Internet to exteapolate this observation of a well known and occurance into a whole new scientific phenomena involving metal particle fields and now the requirement to invent a special name.
It is all quite unbelievable really.
I shall call this Internet phenomena the "Lu Zuckermann Effect".
And Lu, we do miss your posts here mate - the prune is just not the same these past years. RIP mate.
Last edited by helmet fire; 4th Aug 2013 at 08:00.
