Unfortunately, not every aircraft is lucky enough to be the bird of the sky. Some of them had an opportunity to try while others have never even left the ground.
1. Caproni Ca. 60
One of the earliest and most visually striking of early aircraft was what became known as the Caproni Ca. 60. It was an Italian 9-wing monstrosity that carried eight separate engines along with the human payload. It was designed not only to fly but also to stay afloat on bodies of water. After construction, it was tested in early spring of 1921. The results were promising enough to warrant a second attempt. This follow-up flight ended with the plane crashing down into Lake Maggiore on the Italian/Swiss border and breaking into thousands of pieces. More pieces fell off into the water as the plane’s remains were being dragged to shore. The remaining pieces are currently on display in two Italian museums.
2. H-4 Hercules
Howard Hughes’s famous H-4 Hercules (also known as the “Spruce Goose”) was another plane known for its short shelf life, in this instance due to unfortunate timing. Planned during World War II, the plane would be designed to carry more than 700 soldiers or two armored tanks. It was made of birch, not spruce, and had the longest wingspan known to history: 321 feet (a Boeing 747-100B, by comparison, has a 196-foot wingspan). It made one short test flight in November of 1947 but was almost immediately made redundant by the ending of the war.
3. Republic XF-84H
The Republic XF-84H was a plane that looked great on paper: a fast airplane with a turbine engine and a supersonic propeller. But from its first flight in July 1955, there were problems. First, it could take up to 30 minutes to warm up before it could leave the runway, making it practically useless for military missions. Then there was the noise. Legend has it that once up to flight speed, the plane’s noise could be heard up to 25 miles away under ideal conditions. Headaches and severe nausea were reported by the pilots and spectators nearby. The U.S. Air Force decided to cut its losses, and the program pursuing improvements to the XF-84H was closed down in 1956.
4. Convair NB-36H
If the XF-84H can claim to be the loudest known airplane, the Convair NB-36H can safely hold the title of the most dangerous one. The bomber plane was powered by small nuclear reactors within the plane itself. The Convair took a functioning plane, gutted it, and installed such items as 12-ton lead panels and thick lead glass in the windows. Two nuclear engineers were required on the test flights. The main advantage of a plane such as the Convair is that it could stay airborne without needing to refuel for long spans of time. Almost 50 successful test flights between the autumn of 1955 and the spring of 1957 were performed (over largely unpopulated areas of Texas and New Mexico), but the plane was taken out of circulation anyway.
5. HZ-1 Aerocycle
While not technically a plane, the HZ-1 Aerocycle belongs on this list primarily for its novelty. Intended to let soldiers maneuver easily over enemy lines, the HZ-1 was basically a one-man open-air platform helicopter. The steering was done by way of the soldier shifting his weight in the direction he wanted to go, much like the navigation of modern Segways. After the military expressed interest in the airborne vehicles, three manufacturers began to build prototypes. New bells and whistles were installed such as large fuel tanks and water landing equipment.
Despite the possible military uses, the HZ-1 project was abandoned in the 1950s due to problems with the vehicle itself and difficulties in training military personnel to fly the mini-copters.
6. McDonnell XF-85 Goblin
The McDonnell XF-85 Goblin was an American prototype fighter aircraft conceived during World War II by McDonnell Aircraft. It was intended to be deployed from the bomb bay of the giant Convair B-36 bomber as a parasite fighter. The XF-85’s intended role was to defend bombers from hostile interceptors, a need demonstrated during World War II. Two prototypes were constructed before the program was terminated.
The XF-85 was a response to a United States Army Air Forces (USAAF) requirement for a fighter to be carried within the Northrop XB-35 and B-36, then under development. This was to address the limited range of existing interceptor aircraft compared to the greater range of new bomber designs. The XF-85 was a diminutive jet aircraft featuring a distinctive egg-shaped fuselage and a forked-tail stabilizer design. The prototypes were built and underwent testing and evaluation in 1948. Flight tests showed promise in the design, but the aircraft’s performance was inferior to the jet fighters it would have been facing in combat, and there were difficulties in docking. The XF-85 was swiftly canceled, and the prototypes were thereafter relegated to museum exhibits.