A massive turbojet, stretching 27 feet long, collects dust along a wall of old experimental engines in GE Aviation’s storied Building 700 factory in Evendale, Ohio. Too large to fit in the company’s propulsion museum, the lone-surviving GE4 turbojet is a stunning relic from an era when everything in commercial aviation seemed possible.
The engine’s origins date back to New Year’s Day of 1967 when the U.S. government announced with great fanfare that the GE4 would power America’s first commercial supersonic transport (SST). The engine became a great GE engineering feat—and with it, the promise of billions of dollars in revenues and thousands of jobs.
But it was not to be. Just five years later, the U.S. Congress killed the enormous government-funded aviation project, and the Europeans went on to introduce supersonic passenger travel to the world with the Concorde jetliner.
Any crafty GE engineer can tell you that futuristic engine developments advance the science and art of jet propulsion. This was certainly the case with the GE4. Its unique aerodynamics, high-temperature materials and intricate cooling schemes in the turbine section allowed it to become the most powerful jet engine of its era. Indeed, the GE4 remains an enduring symbol of GE jet propulsion ingenuity even though it never became a production program.
The SST saga in America unfolded in 1962 after the French and British governments formalized a joint technical team to develop a supersonic passenger jet called the Concorde. Not to be outdone, the Soviet Union announced its own supersonic transport called the Tupolev Tu-144. Unlike the Concorde, the Tu-144 failed technically and was shelved.
In the U.S., aircraft and engine manufacturers quickly pursued government-sponsored supersonic aircraft studies. In 1962, the Evendale team received a Federal Aviation Administration contract award to study SST propulsion concepts involving compressor aerodynamics, combustion temperatures, turbine-cooling systems, materials and exhaust augmentation systems.
Having teamed on the U.S. Air Force’s high-speed XB-70 bomber, Boeing and GE naturally worked together on a full-blown SST competition launched by the U.S. government in 1964. Boeing’s 2707 aircraft design called for “variable geometry” wings that are straight at takeoff and then move closer to the fuselage at higher speeds. The GE4 engine for the aircraft was based heavily on the J93 turbojet powering the XB-70.
Boeing and GE had an inside track. In 1965, the J93-powered XB-70 bomber achieved Mach 3, three times the speed of sound, after being airborne for 62 minutes at altitudes beyond 70,000 feet. An aircraft of this size and weight had never traveled so high and fast. The J93 turbine-cooling innovations were critical to the GE4 for the Boeing SST project.
When the Boeing 2027 and GE4 engine were selected for the SST program in 1967, newspapers called the program America’s largest airplane project ever. The four-engine 2707 was designed to carry 350 people at 1,800 miles per hour. Boeing forecasted the aircraft’s entry into service by the 1970s and a 700-aircraft production run by 1990. GE forecasted $4 billion to $7 billion in jet propulsion business over the next 20 years with hundreds of employees to be hired at Evendale.
The GE4 was the world’s first large commercial jet engine with an afterburner. GE designed the engine for thrust levels beyond 60,000 pounds; it would be optimized to operate at Mach 2.7 cruise speeds at 60,000 to 70,000 feet. In short order, the GE4 became the world’s most powerful turbojet by producing 69,900 pounds of thrust during ground tests in Peebles, Ohio. (The SST program led to the construction of Evendale’s unique dual-cell altitude test facility, which is used to this day.)
However, trouble was looming. By mid-1968, Boeing pushed out the aircraft service entry to the 1980s. Some Congressional leaders loudly objected to such high levels of government funding for a private commercial enterprise and questioned its economic and environmental viability.
GE and Boeing were able to keep the SST program going until March 1971, when Congress killed it. Senator William Proxmire of Wisconsin, a leading Capitol Hill dissenter, distributed champagne in plastic cups on the Senate floor after the program went down in a 51-46 roll call. While Proxmire cheered, GE promptly announced 1,500 layoffs in Greater Cincinnati, a loss equivalent to $14 million annually for the local economy.
That May, a Congressional delegation moved to restart the SST program, but Boeing and GE demanded reimbursement of termination costs from the original program before proceeding. GE’s position was that the government should finance 100 percent of a new project, compared to 90 percent for the original one. With GE and Boeing standing firm on their demands, interest in restarting the program eroded on Capitol Hill.
Back-to-back cancellations of the XB-70 bomber and SST created great anxiety and pain at GE Aircraft Engines. In 1971, GE’s aviation plants eliminated 7,000 workers, dropping overall employment from 27,000 to 20,000.
“We had a damn good engine for the SST, and I was always unhappy that we didn’t have the opportunity to use it,” wrote the late GE Vice Chairman Jack Parker in his memoirs. Equally troubling, GE’s massive commitment to the SST led the company not to compete for a new four-engine jetliner being developed by Boeing. It was soon called the 747 with the nickname “Queen of the Skies.” Ouch.
Despite the heartaches, GE Aviation proved remarkably resilient. The company’s CF6 commercial turbofan family, launched in 1968, proved wildly successfully in the 1970s and 1980s on several twin-aisle jumbo jets, including subsequent versions of that same Boeing 747. In 1972, GE Aviation’s Lynn, Massachusetts, operations launched the T700 turboshaft engine with the U.S. Army, which became the most popular helicopter engine in the Western World for a half-century.
And within months of the SST cancellation, GE Aviation head Gerhard Neumann forged a strong relationship with Rene Ravaud, the head of the French engine company Snecma, known today as Safran Aircraft Engines. Over the next several years, they would launch a joint engine company called CFM International.
It went on to sell more jet engines than any company in aviation history.