# How significant is the static buildup on the blades of the main rotor? And some questions related to this [duplicate]

1) Usually, a static charge is built on the helicopter when it flies through the air. If a person touches the helicopter before it touches the ground can that person get electrocuted because of the potential difference? 2) How significant is the static buildup on the blades of the main rotor? Are they grounded to the airframe of the helicopter? 3) What happens if a person jumps right into the helicopter while it's hovering, without completing the circuit with the ground? Like in the Matrix (1999), when Morpheus jumps off a building into a helicopter?

• I don't have any evidence, but anecdotally I have been warned that grabbing an under-slung load before it touches the ground can hurt. I have never felt a shock, but have only worked under smaller helicopters. I have not been told this shock is dangerous, but again this is anecdotal advice from old guys at work, I would be interested in how much charge can accumulate on a large one. Commented Aug 13, 2020 at 8:19

## 1 Answer

1) Technically, yes, it's possible to be electrocuted by a static discharge. The chance of it happening is so vanishingly small, though, that it's not generally a concern. A helicopter simply doesn't have the capacity to store enough electrical energy to be a direct danger. The real threat from static electricity is that it can potentially ignite a fuel spill, or something of that nature.

2) Depends on how you define "grounded". The linkages are coated with grease, which typically has a pretty high resistance. This means that low voltage (where "low" in this case can be up to 500 volts) across the junction probably isn't going to generate a meaningful current. However, static charges routinely exceed 10,000 volts, which isn't going to be affected by a thin layer of grease. So, you can generally consider the whole plane to be at the same potential.

3) Same thing that happens if you're on the ground and touch it. When you touch metal, you'll get a spark, yank your hand back, probably shake it a few times if the spark was particularly bad, and resolve not to do that again.

• That's a great explanation, but regarding question 3. When on the ground the static electricity is low, if you're talking about touching the surface of a vehicle, which is most likely to have more or less conductive landing gear or tires. That's why I don't exactly understand why a person attached to a hovering helicopter can grab a hand of another person who jumped from a building, being at different potentials they can be both safe and sound in real life, or may be through the air gap between the two people, that is narrowing as they get closer, the potential difference neutralizes? Commented Mar 1, 2020 at 11:52
• @PaulJ. Think of two water tanks with a different level of water in each. Connect them, and water will flow from the higher tank to the lower until they're equalized. That's what happens when two objects at different potentials are connected, a current flows through the connection until they equalize. That brief current flow is what generates the spark, what stimulates the pain receptors, and what can cause damage if it's big enough. It doesn't matter why the electricity flows, it just matters how much, and a helicopter doesn't have the capacity to generate a dangerous amount of current. Commented Mar 1, 2020 at 22:50
• note on #3, modern helicopters are electrically bonded from the blade tips to the skids for lightning protection. Commented Aug 13, 2020 at 8:20
• It should be noted that, when a helicopter is involved, even a moderate to mild shock can be fatal or debilitating if, as a result of the shock, you fall out of the helicopter. Sure, at best, you get some bruises and scrapes, but the worst can range from spine fractures to falling on the ground and then getting bashed to death by the helicopter's wheels or skids because helicopters tend to move around quite a bit, and suddenly, when landing. Commented Nov 12, 2023 at 6:47