Sikorsky Firefly is the electric helicopter that has been built but never flown. How do such histories happen?
If the design looked so unsafe that there was not enough courage of trying, why this was not discovered much earlier? If they changed they mind, lost the investor, why not to try at least once anyway if there is already a machine standing ready to power up? Is there any certification for even the first ever flight a prototype may fail to pass?
Stories like "a single prototype was tested but not more ordered" look much more logical (they did not like it after the tests).
What are the most usual reasons behind the "built, never flown" histories?