The Republic XF-84H “Thunderscreech”: A Symphony of Speed and Dissonance

The 1950s were a time of rapid technological advancement, particularly in the field of aviation. While jet engines were taking the world by storm, promising unparalleled speed, Republic Aviation was exploring a different path: a turboprop that could combine jet-like performance with the long-range and low landing speed of propeller-driven aircraft.

This ambitious project resulted in the infamous Republic XF-84H “Thunderscreech,” an aircraft so loud it earned its nickname and a place in aviation history.

Development and Historical Significance

The XF-84H was born from the desire to bridge the gap between the emerging jet age and the reliable performance of propeller aircraft.

It was based on the successful F-84F Thunderstreak fighter-bomber, but with significant modifications.

The airframe was adapted to accommodate a powerful Allison T40 turboprop engine, essentially two turboprop engines mounted side-by-side, driving a supersonic propeller.

This engine promised incredible power and thrust, potentially pushing the boundaries of speed and performance.

The XF-84H represented a bold attempt to push the boundaries of aviation technology.

It was a time of experimentation, and the Thunderscreech embodied the spirit of innovation and the relentless pursuit of speed.

While the jet engine was quickly becoming the dominant force in aviation, the XF-84H offered a different perspective, showcasing the potential of turboprop technology and its unique advantages.

Technical Specifications Overview

• Crew: 1
• Length: 51 ft 5 in (15.67 m)
• Wingspan: 33 ft 5 in (10.18 m)
• Height: 15 ft 4 in (4.67 m)
• Empty weight: 17,892 lb (8,115 kg)
• Gross weight: 27,046 lb (12,267 kg)
• Maximum speed: 520 mph (837 km/h)
• Range: 2,000 mi (3,200 km, 1,700 nmi)
• Service ceiling: 40,000 ft (12,192 m)
• Rate of climb: 5,000 ft/min (25 m/s)

‘Loudest Ever’: Operational History and Challenges

Only two XF-84H prototypes were ever built, and their operational history was short-lived and plagued by problems.

The supersonic propeller, while offering incredible acceleration, generated a deafening noise that could be heard for miles.

This noise, coupled with severe vibrations and handling issues caused by the powerful torque, made the aircraft a nightmare to fly.

Test pilots reported difficulty controlling the aircraft, and most flights ended in emergency landings.

The constant supersonic blade tips created a continuous sonic boom that rattled nerves and equipment, making it a nuisance at best and a safety hazard at worst.

One serviceman, unaware of a nearby test run, was reportedly incapacitated by the noise for 30 minutes, highlighting the sheer intensity of the sound.

The Legacy of the Thunderscreech

Despite its operational failure, the XF-84H left a lasting mark on aviation history.

It showcased the potential of turboprop technology, even though the specific implementation in the XF-84H proved to be impractical.

The program served as a valuable learning experience for future aircraft development, highlighting the importance of balancing innovation with practicality and addressing fundamental challenges before pushing the limits.

The XF-84H also led to the development of the ram air turbine, a vital emergency power source used in modern aircraft.

This system, which deploys into the oncoming air after engine failure to maintain power for vital onboard systems, originated from the XF-84H program, demonstrating that even failed projects can contribute valuable advancements to the field.

Today, the sole surviving XF-84H is on display at the National Museum of the United States Air Force, serving as a reminder of the daring spirit of aviation and the importance of learning from both successes and failures.

The Republic XF-84H “Thunderscreech” may not have achieved its intended goals, but it remains a fascinating and cautionary chapter in the story of aviation, forever remembered as the loudest aircraft ever built.