It’s pretty tempting to get behind the wheel of a flying saucer! But, when it came to this UFO, inspired flying machine, the cost was just too much, estimated at $10 million apiece, according to Aviation CV. Not only were the costs exorbitant, but the other problem with the project was that the designers and engineers grappled to get the Avrocar more than a few feet off the ground without facing major problems.
After some tweaks, production commenced in 1958, but the engineers built only two models in two years. Throughout testing, the Avrocar had unresolved thrust and stability problems that limited it to a low-performance flight envelope. And so the Avro Canada VZ-9AV Avrocar was no more.
Sikorsky CH-37C Mojave
Introducing this bug-eyed monstrosity; The Ch-37C was a huge, heavy-lift helicopter, that experienced its first-ever flight in 1956, it was also one of the last helicopters to use a piston engine, which was even bigger, heavier, and sadly less powerful than the turboshaft engines. It wasn't all bad though, as the helicopter did help to recover spy satellite film capsules that dropped from space via parachute.
It did provide some decent services but it was terribly strange-looking, which, as it might come as a surprise, is of somewhat importance, even for NASA.
LTV XC-142
Another experimental gem we have here. The XC-142 was a tri-service tilt-wing aircraft created to investigate the operational suitability of vertical/short takeoff and landing transports. After the first transitional flight with vertical take-off that took place in January 1965, there was some hesitation over whether or not to continue.
The vertical take-off that resulted in the helicopter being changed to forward flight and ultimately land vertically was perhaps a little too complicated. Five models were manufactured, as a large, boxy fuselage with a tilted rear area featuring a loading ramp. The wingspan was 67 feet and 58 feet long overall. After the five models, they ceased to produce it.
Kellett-Hughes XH-17
One of the main purposes of a helicopter is to hoist large and oversized loads to places that traditional planes cannot access. So when the Hughes Aircraft Company designed the largest helicopter in the world, the XH-17 in 1952, people were delighted.
It consisted of a 120-foot rotor system but in the middle of the testing stage, the XH-17 showed that it was not up to the task as flames began to rise from the jet engines on the rotor tips. Apparently, those as far as eight miles away from the helicopter could hear the monstrosity burning to ashes.
Hughes H-4 Hercules
This prototype airlift flying boat certainly looked the part. Designed and built by the Huges Aircraft Company, the Spruce Goose, as it was colloquially known, was supposed to be used for transatlantic flights during World War II, but ultimately wasn’t completed in time.
When you consider the fact that the Spruce Goose was built primarily from wood, the amount of manpower allocated to making it, and its limited use, there were plenty of reasons why this plane should never have been made in the first place. But probably the biggest problem was how much it cost to make ($23 million in total), with plenty of cost overruns along the way.