One question that came up from Crazy Aircraft #10 was, “what kind of engines is he using?”

He is using a fairly new type of centrifugal jet engine that was originally created for model radio-controlled airplanes. By putting four of them together, he gets enough thrust to fly.

One company that makes these engines is JetCat. You can see their line-up of jet engines here:

JetCat turbines

They are not cheap. But they are small and light and powerful. The Titan Turbine weighs only 3.1 pounds and is 4.4 inches in diameter but it produces 34 pounds of thrust. Put four of those together and you have 130 pounds of thrust.

How much thrust is that? For comparison you can look at this article (which is fascinating):

How two brothers from Dayton added a new twist to airplane propulsion

You can see that the Wright Brothers’ original airplane produced about the same thrust: “the average measured static thrust was between 132 and 136 pounds (that is, each propeller produced a thrust of between 66 and 68 pounds) when the propellers were powered at a nominal rotational speed of 350 rpm.” That engine weighed 170 pounds, never mind the weight of the propellers and chains. The whole Wright flyer (with pilot) weighted about 700 pounds. So today you can get the same thrust out of four jet engines weighing only 12.4 pounds.

The thing that makes these jet engines so small, light and reliable is a centrifugal design. This article has a nice explanation and diagram:

The model jet engine

From the article:

model jet engine design can vary from one manufacturer to another, but they all work on the same principle. The most common type nowadays is the centrifugal flow turbine, as opposed to the lengthier axial flow turbine. A centrifugal turbine mostly differs in the stage of compression – air entering the turbine is thrown outwards as it passes over the spinning impeller. The air hits against the inside of the can and so is compressed greatly, before passing into the combustion chamber. This intense compression increases the temperature of the air, as well as the pressure.

The fuel, which is nearly always kerosene (‘Jet A1′), is introduced into the combustion chamber as a very fine spray, and so mixes easily with the now very compressed air. This fuel/air mixture is then ignited by a small glow plug, much the same as the one found on a 2 or 4 cycle model airplane engine.

As the fuel/air mixture ignites and explodes within the chamber, it is forced rearwards towards the turbines. The turbines accelerate the velocity of the passing gases, and increase the pressure of them too. The gases (exhaust) finally get squeezed through the narrowing jet pipe at the very rear of the engine, exiting at great speed and pressure, thus generating the high levels of thrust.
The turbines are connected to the front impeller by way of a main shaft, so that they power the impeller as they spin.

For more info see: How jet engines work