Back in a day when America was running rich on ingenuity and poor on common sense, the U.S. Forest Service decided to make a bold experiment in lighter-than-air flight. The ultimate balloondoggle ensued.
The Piasecki PA-97 Helistat was an American experimental heavy-lift aircraft, built by Piasecki by fastening four obsolete helicopters to a framework beneath a helium blimp.
The PA-97 was built under a 1980 U.S. Navy contract for the Forest Service to demonstrate a heavy vertical air lifter for harvesting timber from inaccessible terrain. The single demonstrator used a Navy ZPG-2W blimp and four Sikorsky H-34J helicopters. The combination of a large blimp with powered lift made the 343 foot long helistat the largest dynamic lift aircraft in the world.
The aircraft crashed shortly after takeoff on one of their early test flights killing one of it’s pilots in the process. The airframe reacted poorly after the craft was hit with a strong gust of wind. The resulting vibration caused structural failure as the starboard rear helicopter broke off its mounting, its rotors cutting into the gasbag.
Needless to say the project was abandoned after the disaster.