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Meet the YF-118G – The Stealth Plane That Changed History

YF-118G. Image Credit: Creative Commons.
YF-118G. Image Credit: Creative Commons.

The YF-118G did not make headlines like the F-117 or F-35. But it did have a very clear impact on aviation history that is clear: No experimental airplane said “I am stealth” as the Boeing YF-118G. Meant as a technology demonstrator, the YF-118G was ahead of its time and paved the way for further research and development into low observable and radar evasion characteristics. It only flew 38 times, but it showed the U.S. military that a high degree of stealthiness in airplanes was achievable. It wasn’t produced in numbers, but it displayed ingenuity and flair. For these reasons, this airplane deserves a deeper look.

History of the YF-118G

The YF-118G was a “black program” that flew out of Area 51 (Groom Lake, Nevada) in the 1990s. It was given the moniker, “Bird of Prey,” due to its resemblance to a Klingon space plane in the Star Trek franchise. It was airworthy by 1996 after Boeing and McDonnell-Douglas started working in its “Phantom Works” incubator of top-secret prototype manufacturing in 1992. What was amazing is that the defense contractors did it on the cheap. They spent only $67 million on the project without Department of Defense spending outlays.

YF-118G – Not Meant to Be a Fighter

The affordable price tag was because the Bird of Prey was never going to be a bona fide fighter plane. What was important at the time was developing stealth technology. The YF-118G engineers and designers would test the latest and greatest in low observable flight.

YF-118G – Advanced Manufacturing Practices

Much of the design was conducted via computerized virtual reality and disposable tooling. These were new processes. A single-piece composite structure with gapless control surfaces led to a lower radar signature since there were few seams or gaps along the surface. The engine intake was also shielded.

These aspects contributed to a “rapid prototyping” technique. This meant that the program did not produce one prototype, fly it, and then make a second prototype based on this testing data. Alternatively, much of what the Phantom Works engineers did was computer-aided – a departure from the accepted practices of the time. This got them components that were closer to the final product.

Borrowing Parts for Cost Control and Efficiency

The Bird of Prey was not going to win any awards for flight controls. It did not use fly-by-wire and controls were manual without computer assistance. Many parts like the control stick and throttle, plus the rudder pedals of the YF-118G, were taken from other airplanes such as the V-8B Harrier, F/A-18 Hornet, A-4 Skyhawk. The landing gear was borrowed from civilian airplanes. This saved money and made the design process more efficient.

Cool Design –  Underpowered Engine

The airplane had angular gull-shaped wings, which was quite a departure. It didn’t have a tail section. The wings angled high and low. The entire length of the Bird of Prey was comparable to an F-16.

The propulsion system wasn’t that impressive. As I mentioned before, it was no mighty warplane. The Bird of Prey was powered by a single Pratt & Whitney turbofan engine. This pushed out only 3,190 pounds of thrust with a maximum speed of 300 miles per hour, and a ceiling of 20,000 feet.

The Bird of Prey last flew in 1999 and it was declassified in 2002. Its design aspects were used by Boeing in future aircraft, especially the X-32 Joint Strike Fighter prototypes as well as in its X-45A Unmanned Combat Air Vehicle model.


YF-118G. Image Credit: Creative Commons.

YF-118G Bird of Prey

Image: Creative Commons.


DAYTON, Ohio — Boeing Bird of Prey at the National Museum of the United States Air Force. (U.S. Air Force photo)

In an age when new airplanes have schedule slips and cost overruns, the YF-118G Bird of Prey stands out for having an excellent acquisition history. It did not waste taxpayer money. The stealth technology was emulated by other aircraft. It used off-the-shelf parts without having to re-invent the wheel. And its computer-aided design was efficient. Thus, the Bird of Prey accomplished its overall mission as a stealth technology demonstrator.

Now serving as 1945’s Defense and National Security Editor, Brent M. Eastwood, PhD, is the author of Humans, Machines, and Data: Future Trends in Warfare. He is an Emerging Threats expert and former U.S. Army Infantry officer. You can follow him on Twitter @BMEastwood.

Written By

Now serving as 1945s New Defense and National Security Editor, Brent M. Eastwood, PhD, is the author of Humans, Machines, and Data: Future Trends in Warfare. He is an Emerging Threats expert and former U.S. Army Infantry officer.