The Piasecki PA-97 Helistat was an American experimental heavy-lift aircraft, built by Piasecki by fastening four H-34J helicopters to a framework beneath a helium-inflated blimp envelope. The sole prototype was destroyed during a test flight, killing a test pilot and injuring another four in the course of a single incident in 1986.

https://en.wikipedia.org/wiki/Piasecki_PA-97_Helistat

NSFW Video - https://www.youtube.com/watch?v=4KY3A2HlbzQ - it's barely off the ground when it crashes at ~1:00.