We created the Airplanes > Jets > Jet Accessories & Hardware category for fan units, retracts, mixture controls, etc., which are specialty jet items. This was done after several requests by other members who felt their jet specific items should be allowed to be listed in the Airplanes > Jet category, even if the item itself is not an airplane.

You are correct, there have been a few diesel ducted fan engines flown, but they are all either one off engines, or have been converted from existing 2-stroke glow units.