RogerBW's Blog

Piasecki PA-97 Helistat 19 March 2014

The Helistat was a hybrid airship/helicopter combination, designed for heavy vertical lift.

In principle it's not a bad idea. Compared with a conventional large helicopter, the vehicles it was bidding to replace, it uses less fuel because much of the lift comes from the gas envelope. Of course there's more aerodynamic drag, but at helicopter speeds this needn't be hugely significant.

Because putting a single huge rotor on an airship would be impractical, the Helistat prototype (built under a US Navy contract for the Forest Service, who wanted it for logging in remote places) consisted of a single obsolete ZPG-2W (N-class) envelope, coupled with four obsolete Sikorsky H-34 helicopters (with the tail rotors and booms removed to save weight). The controls were linked together so that the assembly could be handled by a single pilot in one of the helicopter cabins. Everything was linked together by a structural framework.

Test flights were conducted at Lakehurst throughout May and June of 1986, apparently with some success. However, on 1 July, a gust of wind caught the aircraft while it was on the ground, and the landing gear started to shimmy. Some of the helicopters entered a ground resonance state, a state in which the rotors vibrate excessively and generate off-axis lift and turning forces. The pilot correctly increased power to lift off, but one of the helicopter bodies broke free, slicing into the gas envelope. This made the vibration worse, and the framework disintegrated, leading to all the helicopter bodies breaking away; this killed the pilot.

The basic problem seems to have been a woefully optimistic calculation of the stress dynamics of the connecting framework. Given that making it stronger would inevitably make it heavier, and the whole point of the thing was to be light to carry heavy loads, further development was not undertaken.

The SkyHook JHL-40 could be considered a lineal descendant (though the designers wouldn't thank you for doing so), but whether it'll ever actually get built is anyone's guess.

Comments on this post are now closed. If you have particular grounds for adding a late comment, comment on a more recent post quoting the URL of this one.

Search
Archive
Tags 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s 2010s 3d printing action advent of code aeronautics aikakirja anecdote animation anime army astronomy audio audio tech aviation base commerce battletech beer boardgaming book of the week bookmonth chain of command children chris chronicle church of no redeeming virtues cold war comedy computing contemporary cornish smuggler cosmic encounter coup covid-19 crime cthulhu eternal cycling dead of winter doctor who documentary drama driving drone ecchi economics en garde espionage essen 2015 essen 2016 essen 2017 essen 2018 essen 2019 essen 2022 essen 2023 existential risk falklands war fandom fanfic fantasy feminism film firefly first world war flash point flight simulation food garmin drive gazebo genesys geocaching geodata gin gkp gurps gurps 101 gus harpoon historical history horror hugo 2014 hugo 2015 hugo 2016 hugo 2017 hugo 2018 hugo 2019 hugo 2020 hugo 2022 hugo-nebula reread in brief avoid instrumented life javascript julian simpson julie enfield kickstarter kotlin learn to play leaving earth linux liquor lovecraftiana lua mecha men with beards mpd museum music mystery naval noir non-fiction one for the brow opera parody paul temple perl perl weekly challenge photography podcast politics postscript powers prediction privacy project woolsack pyracantha python quantum rail raku ranting raspberry pi reading reading boardgames social real life restaurant reviews romance rpg a day rpgs ruby rust scala science fiction scythe second world war security shipwreck simutrans smartphone south atlantic war squaddies stationery steampunk stuarts suburbia superheroes suspense television the resistance the weekly challenge thirsty meeples thriller tin soldier torg toys trailers travel type 26 type 31 type 45 vietnam war war wargaming weather wives and sweethearts writing about writing x-wing young adult
Special All book reviews, All film reviews
Produced by aikakirja v0.1