PBS TJ80-120 is a compact turbojet engine that has been designed for unmanned aerial vehicles (UAV’s). This considerably modified engine builds on its predecessor PBS TJ80 with all its features and improved key attributes. PBS TJ80-120 offers the best thrust to diameter ratio in its category. We significantly increased the thrust from 202 lbf to 269.7 lbf (1,200 N) and kept the original outside diameter (9.25 in). The engine weight is 28.21 lb including accessories. The possibilities of ground and in-flight windmill start and restart remain. The windmill starting option offers to start the engine under 7 seconds.