Some history and basics of aircraft turbocharging systems

Since the beginning of time, man has always looked for ways to add power to the machines that he’s built. The combustion engine is a prime example of a power source that was just waiting to be improved upon. Since the very beginning of the 20th century, inventors and industrialists alike have looked for ways to boost the performance of engines.

As surprising as it may seem, the typical piston engine converts only about one-third of its potential energy from fuel into useful work. The remaining energy is lost to other forces such as friction and cooling losses. A major part of the potential energy is simply wasted out the exhaust.

Fortunately for us some early inventors found the power boost they were looking for. They found it in the form of turbochargers and superchargers.

Historical perspective
Looking at turbocharging from a historical perspective, you could actually go back as far as the late 1800s, to the German inventor Gottlieb Daimler, or even Rudolf Diesel, who was credited with designing the mechanical supercharger way back in 1896. But for the sake of this discussion, we’re going to start with Swiss engineer Dr. Alfred Buchi. In 1905 Buchi was granted the first patent for a practical turbocharger — a supercharger driven by exhaust gas pulses.

General Electric began to manufacture turbochargers in 1910. In 1915, working as chief engineer for Sulzer brothers research department, Dr. Alfred Buchi proposed and developed the first prototype of a turbocharged diesel engine. Unfortunately, it wasn’t very efficient. It wasn’t efficient enough to maintain adequate boost pressure.

1918 was another important year, probably the benchmark year for aviation-related turbocharging. It was in this year that Dr. Sanford Moss, an engineer for General Electric, carted a 350-horsepower engine to the top of Pike’s Peak in Colorado. And there, in the thin air of the summit of the second-highest mountain in Colorado, at 14,109 feet, Moss was able to boost the power output of that engine to 356 horsepower.

1920 was also an important year in the ongoing history of turbocharging. A turbocharged 12-cylinder Liberty engine was installed on a LaPere bi-plane for altitude tests. They selected this plane, surprisingly enough, because they believed it would be less likely to break up in the event of a long fall from altitude or a violent pull out. A young man named Lt. John Macready was selected to fly the plane. He took it to 33,113 feet! Macready didn’t stop with that altitude. In fact, in a very short time, he became one of the most experienced high-altitude flyers in the world, testing turbochargers from 1917-1923. The highest he flew in his open-cockpit plane was an indicated 40,800 feet on Sept. 28, 1921.

Turbo technology evolved rapidly during the war years. The full strength of blowers was certainly tested during World War II. As you can imagine, the B-17 and the B-29 bombers, along with the P-38 and P-51 fighters, were fitted with turbochargers and controls. The B-36 bomber had six piston engines, each with 28 cylinders. The flight engineer’s handbook for the B-36 states that without turbochargers, the B-36 would require 90 cylinders per engine to achieve the same performance as the turbo supercharged design.

In the late 1980s and early 1990s, the Grob Strato 2C set an unofficial record for piston-powered manned flight when it reached an altitude of 54,574 feet. This unique plane was fitted with the world’s largest all-composite wing at a wingspan of 185 feet. The aircraft was designed to perform missions for communications monitoring, geo-physical research, and pollution and weather observation.

In terms of unmanned flight, in 1986 the Boeing Condor set an altitude record for recip engines at 66,980 feet.

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