"They are MODEL engines and are not "man rated" by the FAA. There are several YT vids showing how they are built and assembled."

A very inappropriate comparison. It's akin to comparing an experimental aircraft with a certified, high capacity transport category aircraft.

The Williams has undergone destructive testing, blade containment testing, is certified for flight into known icing, use on ground, use in rain etc etc.

Using M&D's engine as an example, it has no accessory gearbox so no lubrication; you add extra oil to the fuel like a 2-stroke. It has no electrical system thus no self-sustaining fuel delivery nor command and control. Both of those functions are powered by the battery so it's essential to leave a battery untouched 'for Justin'. It's not approved for ground operation other than maintenance nor for flight in rain. It's a simple, elegant, low weight, low drag thrust source for sustaining. A 'getcha home jet' with only the operating principle as a similarity with Williams and other certified products. And thanks heavens for that! It would be too large, too heavy and too *EXPENSIVE* otherwise.

CJ