Coupled engines to single shaft

[DangerZone]

A new coupled engine with a single shaft output called HT 422 has been shown at Aero Expo 2017 in Friedrichshafen. Each engine has 135HP, enough to continue flying the helicopter or aircraft if one engine quits. Both engines are coupled to a single shaft, and each can power the shaft independently.

I searched the internet to see the regulation about such concepts. Is this still considered a single engine aircraft/helicopter according to FAA rules or is it a multi engine? Does anyone know how EASA regulates aircraft/helicopters powered by such engines? I found some info on the internet that FAA considers aircraft with such engines can be flown with a single engine licence.

Apparently this concept did not evolve because of complicated regulations and certification processes. If anyone has some more examples of coupled engines to a single shaft in the past (and their fate in aviation history) please be so kind to share. The Lear Fan and Soloy Dual Pac are turbine cases, how many lightweight ICE were there in the past?

Some people even tried to patent the idea even though this concept is almost a hundred years old...

http://patentimages.storage.googleapis.com/EP0307452B1/imgf0001.png

https://i.stack.imgur.com/o5qMI.jpg

 

[m9199]

 

[cheapracer]

 

[TFF]

 

[Arthur Brown]

 

[ThadBeier]

 

[Arthur Brown]

 

[Arthur Brown]

 

[BBerson]

 

[Tiger Tim]

 

[lr27]

 

[akwrencher]

 

[max_burke]

 

[nerobro]

 

[cheapracer]

 

[AdrianS]

 

[wsimpso1]

 

[BBerson]

 

[tspear]

 

[Jerry Lytle]