Mom always said not to go too close to power lines, especially when you're in a helicopter, and especially when you're blasting a stream of water from a 30-foot boom. These guys didn't get the memo, but they must have nerves of steel because I get nervous just watching them.
In this clip by Michael Zeltser Aviation, you can see a helo with a water-spraying arm get dangerously close to live power lines so it can power-wash the insulators. There must be a safer way to accomplish this task, but I can't think of a cooler way.
Here's another demonstration, this time with British workers cleaning a live 500,000-volt line:
This looks crazy, but power companies say it's an efficient way to keep the system in tip-top shape. A states that while a washing truck can clean 50 towers per day, a hot-washing helo can clean 150.