1. Brandon

    Brandon New Member

    [Admin: Thread split from: https://www.metabunk.org/posts/46747

    Or is it just friction? Friction creating heat, just like an engine. I don't know, but I know airplane wings don't get hot. I'm just guessing here. It's not static. Static looks like the pic.

    Static from a rotor wing is really colorful and pretty and I can't believe there aren't better pictures than this popping up on google images. I had a job in the army that had me standing under helicopters that were hovering so low I could touch them (they were that low so I could touch them), but I never took pictures.

    How's my science sound, Mick?

    Attached Files:

    Last edited by a moderator: Nov 20, 2013
  2. Mick West

    Mick West Administrator Staff Member

  3. Brandon

    Brandon New Member

    That's static electricity in the picture. It has nothing whatsoever to do with sand. If you think rotor blades hit sand and that makes sparks or flashes of light or whatever, you're wrong. I would love to see actual scientific evidence that what you're claiming is even possible.
  4. Mick West

    Mick West Administrator Staff Member

    It actually seems like the cause of the light is unknown, the photographer himself says a pilot said it's "static", the article I linked says pyrophoric sparks, possibly it's triboluminescence (which is itself not really understood. Whatever it is, it's cool!
  5. MikeC

    MikeC Senior Member

    Anyone who's done any grinding knows what happens when you hit metal with fast moving sand - you get very hot sparks!!

    Try the explanation here


  6. A380

    A380 Senior Member

  7. Brandon

    Brandon New Member

    What's crazy is that I never looked into that corona effect before, at least not reading about it, and now that I have I found bunk. That kid who claims there are pieces of metal flying off rotor blades has succeeded in spreading that disinformation across the entire web. I've stood under 1,000 helicopters, with a static discharge probe and rubber gloves, saw that halo 1,000 times, and I've never been in a desert.

    One thing that kid completely made up was a metal covering for rotor blades. I read a bit of his site, and it seems like he's a creationist or something a bit crazy.

    I always assumed it's static electricity, since helicopters generate a good deal of it, it has to be generated by the rotor blades and you get shocked when you touch a hovering helicopter. It happens all the time too.
  8. Mick West

    Mick West Administrator Staff Member

  9. Mick West

    Mick West Administrator Staff Member

    The UK's MOD does not know what it is:

    http://www.iom3.org/news/call-proposals-rotor-blade-scintillation

  10. Pete Tar

    Pete Tar Senior Member

    A bubble underwater when imploded with a sound wave glows. (sonoluminescence)
    Could this be related?
  11. MikeC

    MikeC Senior Member

    Indeed they can be seen on civil turboprops too - the "silver" strip along the leading edge of a "black" blade - the blade is composite on a metal spar, and the leading edge is usually nickel alloy - one of the places I worked as a QA Engineer was a little maintenance outfit SAFE Air, in Blenheim New Zealand, who have a fairly large prop overhaul shop handling props from all around the Pacific. Replacement of these strips was "steady work".

    All composite blades on aircraft require them because the composite material is too soft to withstand even "gentle" impacts.
  12. Jazzy

    Jazzy Senior Member

    Is.

    Screen Shot 2013-05-30 at 23.05.39.png

    The dust in the air is a transferable insulator, and the helicopter is a giant Wimshurst machine when it meets a sandstorm.

    Screen Shot 2013-05-30 at 23.17.18.png

    http://en.wikipedia.org/wiki/Wimshurst_machine

    I have shot-blasted in the past and never saw a spark. None of the leading edge materials make sparks.

    And Pete - the incredible pressures involved in sonoluminescence aren't created by impacting sand grains.

    It is also the effect experienced by the jumbo that accidentally flew at night through the ash cloud of an erupting Indonesion volcano.

    They were surrounded in static-induced light. The engines streamed light like searchlights - before they expired.

    [video=youtube_share;vPs6XVvrY1c]http://youtu.be/vPs6XVvrY1c[/video]
    • Like Like x 1
  13. justanairlinepilot

    justanairlinepilot Senior Member


    I'm assuming all items were grounded, that's why you didn't see any sparks.
  14. Mick West

    Mick West Administrator Staff Member

    • Like Like x 1
  15. MikeC

    MikeC Senior Member

    Indeed - but shot blasting occurs at a much lower velocity than the ends of helicopter blades move at - shot blasting typically uses velocities of 65-110m/s, A Chinook blade tip, radius 9.15m, rotating at 225 rpm, does about 225m/s - twice the velocity, 4 times the potential impact.

    also most shot blasting uses relatively soft shot in order to remove surface materials such as paint or loose materials such as corrosion, and so as to not damage the underlying strata. Shot that does seek to work the underlying material, such as for shot peening, is generally in the form of round particles, so as to "hammer" the material, not cut it.

    the sand will probably have sharp edges and be very hard.


    titanium and nickel can certainly spark - one of the ways of telling what metal something is made of is to grind it a little and see what sparks come off - titanium gives very hot white sparks, nickel gives dark red ones of short duration.

    on the balance I'll still put a $ on hot metal sparks :)
  16. Jazzy

    Jazzy Senior Member

    • Like Like x 1
  17. Jazzy

    Jazzy Senior Member

    Well those blades do wear away very quickly in sandy conditions.

    But also the static-inducing effects of particulates are very much stronger and permeate through all aspects of atmospheric interactions. I wonder how that helicopter would have appeared at night. Erupting volcanoes are very interesting in the dark.

    True. And the cabinets were well lit, which wouldn't have helped. But even at the time I was curious enough to look for it, as I expected some static to be there. Sometimes shot blasting was external to cabinets. But there again, Hampshire was a pretty damp place in the early sixties...
  18. pseacraft

    pseacraft Active Member

    Jazzy - I do believe the pictures of the chinhook were all taken at night. The camera settings just make it look more light out than it is to our eyes as the camera sensor is more sensitive.
  19. Mick West

    Mick West Administrator Staff Member

    Yes, the phototgrapher, Michael Yon, says:
    http://www.michaelyon-online.com/the-kopp-etchells-effect.htm



    He's used a Canon 5d MkII, with some fast glass, $10,000 worth of gear. Possibly one that was modified:

    http://www.michaelyon-online.com/camera-auction.htm


    He also says


    So it would seem this is considerably different to how the scintillation would appear to the naked eye.
  20. Jazzy

    Jazzy Senior Member

    Yes, I gathered it was after dusk somewhat, but not using a special camera.

    Particulates in fast moving air always generate static electricity. Hence explosions in coal mines and flour mills, or wherever the powder is combustible. The only way I know to rid that potential from a dusty area is to use that Evergreen jumbo to drop large amounts of water from above the area in advance of the helicopters. Cheaper than a million hippie ionizers?

    "Veritably crackle" isn't static, eh? :)
  21. Mick West

    Mick West Administrator Staff Member

    Sure sounds like it. But I'm sticking in the "not sure exactly what causes it" camp for now :)

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