The Cold War era was a period of significant technological innovation, including the development of various aircraft. Some of these aircraft, like the SR-71 and Fairchild Republic A-10 Warthog, were highly advanced. However, the era also produced some of the most bizarre aircraft designs, such as Avro Canada’s modern-day UFO, Northrop’s TACIT Blue stealth aircraft, and the peculiar Thunderceptor.
One of the most notorious aircraft from this era was the XF-84 Thunderscreech, a plane that was so loud it often made ground crew physically ill. The Thunderscreech held the world record for the loudest aircraft ever made due to the shock waves thrown outwards by its unique propeller design. This plane was a unique design born out of a unique need during the early development years of the jet engine. The navy needed aircraft with short take-off runs so they could take off from aircraft carrier runways to gain a competitive advantage near enemy territory.
The Thunderscreech was a supersonic propeller design, a propeller designed to spin faster and achieve much higher top speeds than a conventional propeller. Creating a propeller capable of providing the thrust needed at these higher speeds was not easy. The propeller efficiency can also be thought of as the ratio of power in the form of thrust produced by the propeller to the power actually produced by the engine.
The propeller of the Thunderscreech was rotating at supersonic speeds even when it was on the runway. The propeller of the Thunderscreech was much shorter in length to delay the shock wave formation for as long as possible, by reducing the circumference the tip needs to travel during a single rotation. This reduced the tip velocity, a propeller with half the radius will have half the tip velocity, even if it is spinning at the same angular velocity.
The Thunderscreech had a variable pitch propeller, meaning the propeller could change its angle of attack at different speeds to optimize efficiency. The propeller blade twists along its length to ensure each part is working efficiently, but the forward movement of the plane also affects this angle of attack.
The Thunderscreech had a coupled engine, two engines connected together to power a common drive shaft. This was done to reach the total power needed, rather than developing a completely new engine. The coupled T-40-A-1 engines of the Thunderscreech were placed inside the fuselage to avoid additional drag and control issues in the event of an engine failure.
However, the Thunderscreech was not safe to fly. Test pilots had to make emergency landings after 10 out of 11 flights. The plane was so unreliable that it flew with its ram air turbine constantly deployed just as a precaution. The plane violently vibrated from the two drive shafts spinning at 14,000 RPM on both sides of the pilot, the sudden rolling due to propeller surges, and of course, the immense sound that was capable of knocking people over. The plane never got past the testing phase, and the program was soon cancelled.
1. The Cold War was a period of innovation and technological development, resulting in the creation of both successful and unsuccessful aircraft designs.
2. The Thunderscreech was a unique plane designed during the early development years of the jet engine. It was created to have a great climb rate and top speed.
3. The Thunderscreech was a supersonic propeller design with a propeller capable of spinning faster and achieving much higher top speeds than a conventional propeller.
4. The Thunderscreech had a variable pitch propeller, meaning the propeller could change its angle of attack at different speeds to optimize efficiency.
5. The Thunderscreech had a coupled engine, two engines connected together to power a common drive shaft. This was to ensure the plane could operate at the large range of speeds it was expected to encounter.
6. The Thunderscreech had a powerful coupled engine with a horsepower of 5850, nearly four times more powerful than a typical Supermarine Spitfire.
7. The Thunderscreech had a T-tail configuration, which was a modification from the F-84F Thunderstreak jet fighter it was based on. This design was done to get the stabilizer out of the way of prop wash and the turbulence associated with it.
8. The Thunderscreech had an anti-torque vane just behind the cockpit. This vane was deflected 45 degrees on take off and landings to cause a counteracting lift that acted around the rolling axis of the plane.
9. The Thunderscreech had a ram air turbine that was constantly deployed as a precautionary measure because the engine was so unreliable.
10. The Thunderscreech was so loud that it often made its ground crew physically ill. The power of the sound waves emitting from the plane were capable of knocking people over, and on one occasion caused an engineer working on the plane to suffer a seizure.
11. The Thunderscreech never got past the testing phase due to its numerous issues, including the unreliable engine, violent vibrations from the two drive shafts, sudden rolling due to propeller surges, and the immense sound it produced.
12. The program for the Thunderscreech was soon cancelled.