American Helicopter XH-26 tip jet helicopter - photo and video

[Toolmaker51]

2 hours aloft? Ok, I'm impressed. Couldn't be more than a 20 gallon tank, and under pilot for low CG.
Has to be while a potentially less efficient power, it leaves off a heavier drive, piston or turbine motor, all the added controls. That weight eats fuel, the hardware consumes maintenance time.