I am familiar with tip jet powered helicopter experiments. Is there any aircraft that use/used this mode and would it be useful to use a tip jet driven prop on aircraft instead of piston or turbine power?
There was a study done on the use of tipjets in civilian aircraft in the 1950's, if I can find the source I'll edit it into this answer. In any case, the conclusions from that study were as follows:
Because of the fundamental inefficiency of subsonic ramjet propulsion, a tipjet-powered propeller "engine" in the 100 to 150 horsepower-equivalent range was completely uncompetitive with piston power. The fuel flow rate required to run the tipjet prop was excessive.
The tipjet-prop plane had extremely limited range if carrying the same amount of fuel as the piston plane, and no useful load if it carried enough fuel to match the range of the piston plane.
Only experimentally, such as the CL400 tip ramjet experiments. It doesn't really work because if one quits, your airplane turns into a pinwheel due to the long arm of the thrust source from the yaw axis unless the wings are very short. Not literally a pinwheel, but it'll want to roll over and crash pretty bad. If they were out on the tips of wings with the kind of span you need to cruise efficiently at high altitude (as opposed to a stubby winged fighter), you'd need a rudder the size of Wisconsin to be able to control it single engine in a low speed departure climb.
Ludwig Wittgenstein investigated the technology while at Manchester University, UK, and even took out a patent. But his experiments in the lab and on a local railway track came to nothing and he never built an aeroplane. He later became famous as a philosopher.
The idea has been revisited now and again ever since, but I never hears of a plane actually flying with a tipjet-driven propeller.