Looking for information regarding baloon/helicopter experiment

I know the video was not fake, but I have no information about it.
I believe I recorded it from a compilation of aircraft accidents but
it was from 20 years ago.
I unfortunately dont have the tape anymore.
The vehicle, I believe - was put together by some contractor for the
forestry service.
It consisted of a large - dirigible type baloon and four big Sikorsky
helicopters (the old "split level" bird which initially was powered by
P&W R98 rotary engines).
The tail sections of the Sikorsky's had been removed and the whole
structure of the vehicle composed of what looked like steel
latticework.
It was a real catastrophe.
An oscillation developed, at least one of the helicpter bodies broke
free of the structure and crashed to the ground from about 40 feet.
I am hoping for ANYONE knowing about this thing to pass on more info!
=THANKS
WavY

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