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So, I was re-watching The Hunt For Red October, (in light of current Russian shenanigans with Sweden), and there was a scene in which a crew-member on the ground was electrocuted by making contact (and presumably grounding) the helicopter, which had picked up a charge in the stormy weather. Can anyone explain more of what is going on here?

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  • $\begingroup$ I realize that this is a decade-old question, but here is a video of a work crew replacing a TV antenna with the help of a helicopter, and you can see at 15:24 in the video that the guy with the grounding hook forgets to use it, touches the new antenna with his hand, and gets a painful shock from it despite his work gloves. $\endgroup$ Feb 26 at 22:23

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In the same way than an aircraft will build static charge on the wings from friction with the air, the same thing can happen with helicopters from fast moving blades.

From a 1962 US Army document:

Any aircraft flying in the atmosphere can be considered as a conductive body located in a highly electrically insulated environment. In such a body, electrostatic charge is generated by three principal mechanisms:

  1. Charge transfer created by a triboelectric effect between the aircraft and the atmospheric particles, such as dust, water, water vapor, snow, etc.
  2. Unbalance of the ionic content of the exhaust gases produced by the aircraft engine(s).
  3. Induction charge due to high electrostatic field gradients which are found occasionally in the aircraft flight path.

Source

Here's a more detailed photo of the US army discharging a helicopter while wearing insulating gloves:

enter image description here SGT Nathan Rodeheaven uses a static probe to discharge static electricity from a UH-60 Black Hawk before his teammate, PV2 Danny Browning, hooks up the cargo to the helicopter. The safety measure prevents the hook-up man from being electrocuted in the event there is accumulated static electricity. Photo: Kristin Molinaro

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    $\begingroup$ "This effect is also amplified by moisture in the air" - Isn't it generally the opposite? Higher humidity = lower resistance to ground = less static build-up. $\endgroup$
    – nobody
    Oct 28, 2014 at 3:27
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    $\begingroup$ Also check out videos of workers being lifted to high voltage power lines by helicopter. In that video they energize the helicopter to the 500kV line voltage so they can work safely (there are some 765kV videos too). See also this question and this article. Although I'm not sure how interesting my comment is, since I don't really know what they do when they land... $\endgroup$
    – Jason C
    Oct 28, 2014 at 5:02
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    $\begingroup$ @AndrewMedico The moisture contributes charge just like the air does, see P-static. $\endgroup$
    – fooot
    Oct 28, 2014 at 14:34
  • $\begingroup$ Many amateur radio operators are familiar with "rain static", a.k.a. precipitation static, which is radio noise resulting from a voltage gradient in the air caused by rain and cloud droplets interacting with each other. $\endgroup$
    – rclocher3
    Apr 15, 2021 at 1:17
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    $\begingroup$ @JasonC According to the video description, those are AC power lines with a phase-to-ground voltage of 288,600 volts. That means that the peak voltage relative to ground is about 400,000, which means that that helicopter is charged up to 400,000 V, then discharged down to 0 V, then charged down to -400,000 V, and then discharged back up to 0 V, all fifty times a second! If my back-of-the-envelope calculations are correct, a person touching that helicopter would probably be able to feel it, but would not be injured. (A person touching that helicopter and the ground would be killed.) $\endgroup$ Apr 15, 2021 at 19:17
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I am a Naval Aviator and as part of my water survival training, I was deposited by boat off the coast of Florida and picked up by helicopter. It was a huge point of emphasis that we let the helicopter's rescue hook touch the water to discharge any built up static before we touched it.

No one in my class grabbed it before it hit the water, so I can't speak to how bad the shock would have been.

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  • $\begingroup$ what do you fly? $\endgroup$ Feb 3, 2020 at 23:37
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    $\begingroup$ I just retired. I flew and instructed in the P-3A/B/C, EP-3E, and the T-6A. $\endgroup$
    – Scooter
    Apr 17, 2021 at 22:53
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I work for a Christmas tree farm and we harvest our trees out of the field using a helicopter. I am the hook man and attach the bundle of trees to the heli, then he takes them to another location. In that breif trip during a rain storm, or even a foggy day static charge will build resulting in a very unpleasant shock. Sometimes bad enough it will contract the muscles in my hand and arm. I’ve been doing this for 3 years and finally invested in some 20,000Vac insulated gloves that are enough to keep this from happening.

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Helicopters in normal weather will build up a static charge, just ask any ground crew for a logging helicopter. Normally the hook will be grounded by dropping it on the ground before the hooker will touch it.

Or a grounding rod will be used to neutralize the static charge.

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I was struck in the forehead in 1983 from the discharge off a CH-53. I was wearing a kelvar helmet which was split down the middle from the strike, heart rate slowed down to 4 beats a minute thought I was a gone. I was stationed at camp Pendleton USMC when it happened.

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    $\begingroup$ I'm sorry, but I can't help being highly skeptical about your remark about "4 bpms" (and a split helmet). Moreover, while this story might answer positively to the title question, it does not address the request for explanation of the phenomena. $\endgroup$
    – Federico
    Mar 1, 2016 at 15:17
  • $\begingroup$ Frederico would like to share more info with you but new to this site is the some way I could talk to you I have read a lot of the studies just need more info and you sound like you have the knowledge Imlooking for $\endgroup$ Mar 1, 2016 at 17:52
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    $\begingroup$ @Federico just gonna say that getting hit in the head with the cargo hook such that it cracks the cranial (or helmet) is not beyond belief: depends on how it was swinging, etc. (Part of why one wears head protection on the flight line in the military) The cargo hook is made of metal and the hover altitude of the CH-53E is high enough for a significant pendulum effect to build up. (draw a mental picture of a two pound weight on a 60' rope, swinging, and hitting your head ...) As to the heart rate, no comment. $\endgroup$ Feb 3, 2020 at 17:30
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Yes they do. I was involved in many HDSs (Helicopter Delivery Service) and would earth the Helo with a sheperds crook and trailing copper linkage - often getting a visible spark. I also took part in the rescue of a few dozen (memory fades on how many) crew from a bombed ship with no hook and earthed the helo myself - yes it hurt.

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We didn’t have a static hook in my day. I will tell you, sometimes the pilots would relieve the static charge by grounding the aircraft themselves. Sometimes, they did not. The static charge would vary From moderate to severe. And, it could even be felt by your partner who was bracing you by the legs. After the first couple of volunteer troopers started flinching from the shock and throwing the hook, me and my buddy got elected/volunteered to do it. We airmobiled the entire battery-sized unit, alternating back-and-forth as hook up man. By the time it was done, we were completely spent LOL. 82nd ABN 2/321 ,B /3-319 1986-89.

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    $\begingroup$ Thank you for your service. $\endgroup$
    – Dean F.
    Feb 3, 2020 at 16:43
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See, CAA CAP 426, Helicopter External Load Operations, April 2006

6.25 Electrical Static Charges and 6.26 Dissipation of Static Electricity and Appendix B Static Electricity Charging Conditions

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    $\begingroup$ Welcome to aviation.SE! This is a useful reference but by itself it doesn't answer the question; we strongly prefer it when you summarize the key points here so that we have a complete, standalone answer. $\endgroup$
    – Pondlife
    Nov 30, 2017 at 16:21
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It sounds like the helicopter had no static dissipators/wicks fitted (or broken ones!), and this resulted in the normal in-flight charge buildup zapping the groundman on the submarine instead.

I'm surprised the helicopter pilots didn't notice that awful noise in their radios well before this became a problem, though!

See What are these things hanging off the trailing edge of the wing? for more details.

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    $\begingroup$ The static wicks are not a magic instrument that would eliminate the static buildup. Air is pretty good insulator and the static wicks can't change that. $\endgroup$
    – Jan Hudec
    Jan 17, 2015 at 11:09

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