In a competitions  between giants there is always going to be a party that losses out  such as the story of Northrop corporation’s YF-23 aircraft which only two prototypes were made lovingly know as  the Black widow 2 and Grey ghost. Today most of the people had forgotten about this  phenomenal aircraft as the aircraft that lost out to the mighty Lockheed Martin YF-22 now known as F-22 Raptor and the aircraft that Northrop produce was anything but unforgettable today.

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In this blog, we are going to dig up the past and tell you why YF-23 was a masterpiece of modern engineering.

In 1980 the United states take a step to come up with a new requirements of a new air superiority fighter under a program called the Advanced Tactical fighter program. In initial stages, the main focus of the united states was on a few features that new aircraft would absolutely need to have it include all aspects stealth meaning the ability to have a reduced radar cross section. The engine should be able to super cruise  which is flying at supersonic speed without the of afterburner, the use of composite material and new alloy in construction processes to reduce the overall weight of the aircraft  advanced fly by wire systems to make the aircraft more maneuverability and finally the aircraft should have short takeoff and landing or STOL features.

The prototypes and flight testing was awarded to Lockheed Martin YF-22 and Northrop YF-23 in 1986.

The YF-23 prototype were 67ft 5inch in length and had a wingspan of 43feet 7 inches which was slightly bigger than its competitors the YF-22 design, giving the YF-23 a slight advantage in range and speed. The prototypes air vehicles PAV 1 and PAV 2 were powered by two Pratt & Whitney YF-119 and two general electric YF-120 after burning turbo fan engines. Both of these engines were able to meet the Advanced Tactical fighter program requirements . however at the end the YF-119 was chosen to powered the winning entry of  Lockheed Martin YF-22.

Both of the prototypes were able to reach at a maximum speed of mach 2.2 and super cruise at mach 1.6. the Northrop prototype was the first to take to the skies  PAV 1 took its first 50minutes maiden flight  on the 27august PAV2 took first shortly after on 26 October.

By all aspect the design of YF-23 was brilliant with some very advanced design elements. The aircraft was configured with diamond shaped wings which allows the designer to reduced the aerodynamic drag at transonic speed between mach 0.75 and mach 1.2. this mean the aircraft have good low speed  performance despite being overall fast jet. The trapezoidal wing setup also offer advantage for high speed flight as well. A small and highly loaded wings such as the YF-23 offered substantially lower drag at supersonic speed than other configurations. Along with unusually shaped wings, the YF-23 also features an all moving v tail in favor of the more traditional vertical fans and horizontal surface. The type of design is sometime called a butterfly tail which is an unconventional design but offers some direct advantage. This configuration the overall expose surface area of the tail which not only leads to less parsitec drag but also make the rudder controls more effective allowing the pilot of the YF-23 to achieve more airspeed and maintain proper your controls during high-speed flight. The cockpit  of the YF-23 was placed very closed to the nose of the aircraft which improves overall pilot visibility. The aircraft had a conventional tricycle undercarriage layout with the internal weapon bay placed on the underside of the fuselage  between the nose  and main landing gears. This mean the aircraft will carry all its weapon inside and not  on wing hard points. This choice were made to maintain all aspects stealth.

The increase in engine performance was a big technological breakthrough for ATF program as it led to the creation of the first super cruising fighter jet in the world it mean that fighter would no longer have to really on gas guzzling afterburners to reach supersonic speeds saving valuable fuel and increasing the overall range of the aircraft. A major challenge for the ATF program designers was to provide stable airflow to high performance engines on an air frame that ‘s hard to spot on radar simply put the issue had to do with boundary layer air that spread around the aircraft fuselage as it flies boundary layer air can flow at different velocities and directions compare to the air that offset from the aircraft ‘s surface, mixing these two stream of air lead to large drops in engine efficiency. At supersonic speed these issue have compounded even more.

The YF-23 features trapezoidal engine inlet with s ducts and some very cleaver solution to make this program go away. The ATF program supersonic jet dealt with this program using elaborate splitter plates to separate the two airflow and maintain uniform supply through the inlet  but those concepts were not very conducive to stealth, even a small gap between the inlet and the fuselage can result in a radar cross-section increase. Thus the designer of the YF-23 came up with an innovative solution. They install gauzing panels ahead of where the fuselage meets the leading edge of the air inlet. These panels had small holes drilled all over than and would suck up the boundary layer air sticking to the fuselage before it entered the air inlet . this air is than vented out through a pair of small doors on the YF-23 upper surface. In effect it acted like an invisible splitter plate of sorts but instead of separating the air it removed it. The system was called the boundary layer control system  and work automatically . This configuration of the inlet coupled with the gauzing panels feed the massive engine compressor with a steady stream of air even at supersonic speed while all aspects of stealth. Unlikely it competitors the YF-23 did not features a trust vectoring engine nozzle. Some say this was a massive disadvantage for the YF-23 in the ATF program. According to the designers of the aircraft they sacrificed a little bit of agility to gain a lot more survivability due to the flat nature of the YF-23 fixed engine nozzles the designers were able to line them with heat ablating tiles . thus reducing the infrared signature or Ir signature of the aircraft to heat seeking surface-to-air and air-to-air missiles. The main weapons system that an enemy will deploy against a low observable stealth air superiority fighter just like the company’s B-2 bomber the heat ablating tiles significantly dissipated the engine nozzle temperature.

During air-to-air combat, the YF-23 prototypes were installed with multiple aerodynamic instabilities which were all controlled by its Fly by wire system. The YF-23 core processor was considered as the most advanced supercomputer of its era performing billions of operations per seconds. The system not mange the flight control system but also but also provide radar, navigation performance data and situational awareness in real time. All these features make the YF-23 a real technological marvel of its era.

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