Your first impression after seeing one or more of the photos featured in this piece might be that these are ‘shopped, painted or feature an astronomical event of some kind. Your assumptions couldn’t be farther from the truth, and believe it or not these beautiful dancing lights over the helicopters’ rotor blades were captured in real time by photographers.
This strange effect, dubbed by pilots the Kopp-Etchells effect in honor of two American and British, respectively, service men who passed away in the line of duty, has been experienced ever since military operations in Afghanistan first touched sand. As helicopters prep their assent, once they touch the sand, dust is lifted by the rotation of the blades and these beautiful arcs of light are formed in the process. What’s peculiar, though, is that this doesn’t always happen – quite seldom actually.
“The halos usually disappear as the rotors change pitch,” wrote war photographer Michael Yon. “On some nights, on this very same landing zone, no halos form.” How come?
Now there’s no military secret to what causes these flickering light circles. The rotor blades of the choppers are covered by a titanium-nickle alloy, which when rotating at high speeds through the air-dust medium causes static electricity. This can be seen on the ground side as well, and it actually causes a lot of headaches. When fueling tanks, be them from helicopters or other vehicles, technicians have to ground these in order to prevent static electricity caused by the pumping to discharge and cause explosions.
This is a theory popular with pilots, which hasn’t actually been proved since no one actually bothered researching this in depth. Kyle Hill wrote a blog post on Nautilus where he proposes a more plausible explanation. Static discharge shouldn’t cause this shower of sparks we’re so fascinated by. Instead, it’s more likely that these actually caused by the millions of tiny metal particles sandblasted by the blades that come into contact with dust particles at high velocity. Earlier I mentioned about how helicopter rotors are covered in a titanium-nickle abrasion strip that prevents the leading edge of the blade from being worn down too quickly by the various particulate hazards of the atmosphere. Sand is harder than the strip, however, so when these two meet, metal particles are sent flying through the air and sometimes these ignite.
Think of a car whose tire explodes and is still moving. The rim that used to be covered by the flat tire is now in contact with abrasive road causing millions of tiny metal particles being dispersed into the air which spontaneously ignite in the air. Also, think of starting a fire by hitting two flits together or better yet a classic cigarette lighter.
Whatever the case may be, we’re glad to see and hear that amid all this misery, pain and suffering caused by war, sometimes “magic” can still sparkle.