Tilt-jet employs jet engines capable of moving to angle their thrust between downwards and rearwards positions in order to achieve VTOL ability.
The best example for that and the only aircraft in service to this day is the F-35B.
I have built my mine using 3 mods, infernal robotics, FuelWings and Tweakable Everything Continued.
By using robotics to allow the engine to be positioned under the center of mass enabled by balancing the weight of the aircraft by adding fuel tanks to the wings and to the rear of the plane. RCS nozzles allow for the aircraft to balance itself in vertical flight.
Get this model: https://steamcommunity.com/sharedfiles/filedetails/?id=2614031073