The concept dates back to the early 1960s, with a one-half scale model of the aircraft being built sometime between 1962 and 1963. The aircraft was an exercise in utilizing specific materials and shapes to drastically reduce the radar cross-section of a tactical aircraft.
From this pioneering design, five Boeing “stealth” patents were awarded, and they only appear to have shown up in public records in the early 1990s, decades after they were officially filed.
The model of Quiet Bird was said to have been tested at Boeing’s Wichita facility in 1962-1963, all of which occurred on a radar range. No actual flight testing of Quiet Bird itself was said to have happened, though. But the tests were highly successful: they proved that it was possible to drastically decrease the radar signature of a tactical aircraft.
Still, the concept was not just designed as a shape to test radar reflectivity. Boeing had full plans to develop it into an actual aircraft. Unfortunately for them, the design ended up being too ahead of its time. Even to be adapted as a forward penetrating observation or attack aircraft, and believe it or not, the military had little interest in it.
This actually makes some sense. At the time, raw performance and increasingly advanced avionics that could allow for either all-weather high-level or low-level penetration of enemy airspace were all the rage. (See also the SR-71, U-2, A-6, and F-111). As it was, this jet wouldn’t have been much of a performer, but it very well could have been invisible to enemy sensors, and with that, who needs performance?
It would not be until about a decade later that the Pentagon would begin considering aircraft designs with low-observable technology as their primary feature set, later dubbed stealth, as a silver-bullet technology worth pursuing with fervor.
When looking at Quiet Bird, especially in these new images and schematics released to us from Boeing, it is amazing how many stealth features that are used in modern day low-observable aircraft designs existed on this 50-year-old concept. The aircraft’s chine-line that separates its smooth, shallowly curved bottom and trapezoid shaped fuselage are key tenets of stealth designs to this very day.
The aircraft’s canted tails and exhaust set well forward of its trailing edge are also key features found on many modern combat aircraft that were designed with signature control in mind. This configuration not only helps with lowering radar reflectivity while still providing stability and maneuvering control, but it also shields the aircraft’s hot exhaust signature from the virtually every angle but from directly above and behind.
Even the aircraft’s gold plated canopy and use of composites structures are all major techniques widely in use today to lower a manned aircraft’s radar signature.
Quiet Bird’s unique low-observable inlet design and curved duct are meant to shield the aircraft’s highly reflective engine face from radar. A similar setup is used on the majority of stealth aircraft designs today, and Quiet Bird’s configuration is especially reminiscent of the X-47A Pegasus unmanned experimental aircraft
In all, a stunning amount of features of Quiet Bird’s design, some of which are below its skin and detailed in these patents (1,2,3), are used to various degree on a whole slew of modern aircraft designed with signature control in mind. These include Tacit Blue, B-2, Have Blue/F-117, YF-23, X-32, F-22, Avenger, Global Hawk, and multiple unmanned combat air vehicles including Boeing’s own Phantom Ray.Even stealthy cruise missiles will instantly evoke Quiet Bird’s configuration. It is almost as if Boeing spectacularly created a Rosetta Stone for stealth technology before it was even “officially” invented.
There is no place where Quiet Bird’s spirit lives on more than in Boeing’s once top-secret Bird Of Prey technology demonstrator. Unlike Quiet Bird, it did get to fly, albeit in the 1990s.
Even through they were separated by three and a half decades from one another, Bird of Prey was a reboot of sorts of Quiet Bird, meant to package a bunch of experimental low-signature and advanced manufacturing techniques together with flat out performance taking a back seat to raw innovation. They are even similar in design.
This airframe paved the way for many technologies that allowed Boeing to step into the 21st century ready to compete in the advanced military-aerospace marketplace. These included rapid prototyping, large single-piece composite structures, 3D design, disposable tooling and a host of low observable innovations.
Boeing is in no way in denial of Quiet Bird’s indirect impact on many of their products, and possibly others, that followed it over the last five decades, they write:
The model and drawings do show some stealth concepts that are used in operation stealth airplanes today, so it would seem that the Boeing engineers working on this project were onto something. The lessons learned on Quiet Bird probably did influence the design of the Boeing AGM-86 Air Launched Cruise Missile
Internally Boeing continued to work on the non-metallic structures aspects that were pioneered with Quiet Bird and that work did eventually lead to the use of increasingly larger and more complex composite structures in Boeing aircraft. In the 1980s Boeing used its expertise in composite (“Stealth”) structures to build the wings and center fuselage structures of the B-2 bomber and today major structures of our commercial jets can be built from composite structures with the primary example being the 787; the first large commercial jet that is primarily made of composite materials.
Even though Quiet Bird remains something of a mystery even to the company that built it, it potentially changes how we commonly look at the advent of stealth technology today. This design was an incredibly well thought out concept that predated the Pentagon’s stealth initiatives of the mid 1970s, including the XST program, which gave us the Have Blue demonstrator and the F-117 Nighthawk, America’s first (known) operational stealth aircraft.
Other aircraft emanated from this time period as well, including the game-changing Tacit Blue Battlefield Surveillance Aircraft-Experimental demonstrator and potentially a whole swath of aircraft that remain highly classified. Although other aircraft, namely the A-12 Oxcart/SR-71 Blackbird, had secondary stealth features, Quiet Bird appears to be the first concept to feature a comprehensive low-observable aircraft design. So while Lockheed largely holds the public spotlight as the harbinger of the “stealth revolution,” Boeing was miraculously there with an eerily advanced aircraft concept nearly a decade and a half before Lockheed’s Skunk Works developed its now famous “hopeless diamond” that led to the historic Have Blue technology demonstrator.With all this in mind, Quiet Bird deserves its rightful place in history, even if only as an uncannily accurate prediction of what was to come decades later from the world of military technology and “bleeding-edge” aerospace design.