Helicopters are dangerous
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The sole prototype was lost during a test flight, killing a test pilot and injuring another four in the course of a single incident.[
I assume there was a pilot in each helicopter
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Especially when you tie four of them together.
Link to video@George-K said in Helicopters are dangerous:
Especially when you tie four of them together.
Link to videoTerrific.
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Unanticipated vibrations. LMFAO
Whoever thought this was a good idea and the people that then allowed it to proceed are freaking idiots.
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@mark said in Helicopters are dangerous:
Unanticipated vibrations.
Looks like the project was from a time before extensive computer simulation of the design was feasible.
The PA-97 was built under a 1980 U.S. Navy contract for the Forest Service to demonstrate a heavy vertical airlifter for harvesting timber from inaccessible terrain. The single demonstrator used a retired Navy ZPG-2W blimp envelope and four Sikorsky H-34J helicopters. The combination of a large blimp with powered lift made the 343 foot (104.57 m) long helistat the largest dynamic lift aircraft in the world.[1]
The helicopters used were aged examples of a long-established design. Their tail rotors were removed, their fuselages shortened and they were attached to a crude tubular aluminum framework beneath the helium-filled envelope. Four freely-castering twin-wheel bogies beneath the framework provided the undercarriage. Criticism has been expressed of the structural qualities and stress analysis of this framework.[3]
Test flights were made from the Naval Air Engineering Station Lakehurst in New Jersey, making use of the long-established hangars for handling large airships. First flight was on 26 April 1986.[4]
On 1 July 1986, the PA-97 crashed immediately after liftoff on a test flight, killing one of the pilots.[3][5]
A gust of wind from the rear of the aircraft induced some movement across the ramp. The undercarriage responded badly to this, the bogies shimmying uncontrollably.[3] Vibration in the framework then coupled with a helicopter phenomenon known as ground resonance.[3] The vibration was sufficient to cause a structural failure as the starboard rear helicopter broke off its mounting, its rotors cutting into the gasbag.[3] The unbalanced lift then made the vibrations worse and the remaining three helicopters broke free.
