The RP-4 was the brainchild of David Rose, a well-known avid speed-chaser with plenty of bomber and fighter jet experience who wanted nothing less than to become the fastest piston-powered aviator. The radical design made it to the build stage but never took to the air, and the pilot scrapped it ten years ago.
The airplane is quite a sight and bears the David Rose signature all over it, from shape to engineering to ambitions. Not one but two monstrous V8s powered the crudely looking aircraft.
One such engine has a 600 ci (9.8 liters) and is suitable for a sky-shredding 2,700 hp. Up that by 100%, and you have enough power to buzz the tower. As unbelievable as it sounds, the plane's overall engineering meant it would have exceeded 600 mph (960 kph).
However, that power would have also torn apart the lightweight frame, so each engine was downturned to about half its capability. Nonetheless, the tandem-mounted engines, each driving its propeller in the contra-rotating assembly, were enough to set a speed record.
The front engine has a direct drive system to move the front prop, while the rear V8 uses a gearbox transmission to bypass its twin and turn the second propeller. The screws consisted of two custom-built four-blade propellers with variable pitch hubs derived straight from NASA's Unducted Fan Technology. To reach and work steadily at 4,800 RPM, each 29-inch-long (72 centimeters) blade was made from eighty-four carbon fiber layers for improved strength and reduced mass.
The sleek slender fuselage was welded from high-strength chromium-molybdenum alloy tubing and covered in thin aluminum sheets. You can tell from the photos that the plane was a very low-drag, high-efficiency design, with a diameter of 31 inches (78 cm) and a canopy bulge of 12 extra inches (30 cm).
A particular cooling system - fitted inside the airplane's wings - proved the best solution to cope with the vast amounts of engine power. Essentially, the wings doubled as radiators, with some 200 feet (61 meters) of tubing running through the 50 gallons (190 liters) of water inside the wings.
For aerodynamic efficiency, the wings were no thicker than three inches (less than eight centimeters). The low-profile complex structure can withstand high stress developed during high air speeds (over 100 pounds per square foot, or 488 kg/sqm).
At 28 feet long (8.5 meters), with a wingspan of just 20 feet (6.1 meters), and a wing area of 58 square feet (5.4 meters), the ultra-compact airplane would have flown in the Unlimited Class at the Reno Air Races.
Initially, the plane only weighed less than 4,600 pounds (2,090 kg), so it was 100 lb (45 kg) short of the minim allowable. The radiator-wing design solved the mass requirements; with the 50 extra gallons (190 liters) of water giving it some 400 pounds (190 kg) of ballast, the plane fell into the category.
The very thirsty V8 engines would go through 145 gallons of fuel (550 liters) every hour, but the plane only carried 100 gallons (380 liters) of 110 high-octane aviation juice.
Anyway, it was more than enough for the minimum eight-minute mandatory run needed to qualify as an official attempt. And while there is no solid data to rely on, we like to fathom that the plane could hypothetically have blast past the 528 mph (850 kph) mark.
Had it done so, it would have become the fastest piston-engine aircraft in the history of flight. The airplane took shape in 2005; six years later, it was ready to begin tests and trials. However, in 2011, following an unrelated incident at an airshow, the Reno Air Racing Association changed the rules for all flying machines, and the RP-4 was no longer qualified to compete.
The man behind the project is as uncompromising as his design. With over 2,500 flight hours for the Air Force and a career as a civilian pilot, David Rose stayed in the world of aviation after his retirement.
He won four gold medals in the "Sport Biplane" category of the National Air Races in Reno, Nevada (a feat he accomplished in five years, between 2000 and 2004, with an airplane he built in just eleven months.)
With a never-quenched hunger for airspeed, in 1999, he purchased NASA's Mach-Buster prototype specially designed for high speed. This piston-engine propeller aircraft aimed to break the sound barrier. It never did, but it served as the inspiration for David Rose's RP-4.
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