Northrop YF-23
| Northrop YF-23 Black Widow II | |
|---|---|
 "Gray Ghost" and "Black Widow II" in flight |
|
| Type: | Air superiority fighter |
| Design country: | |
| Manufacturer: | |
| First flight: |
August 27, 1990 |
| Commissioning: |
Flight tests ended in 1991 |
| Production time: |
never mass-produced |
| Number of pieces: |
2 |
The Northrop YF-23 was a prototype from Northrop , Grumman and McDonnell Douglas for the "Advanced Tactical Fighter" program of the United States Air Force (USAF), in which a new fighter aircraft to replace the F-15C Eagle was sought. It was subject to the competing model YF-22 of the company consortium made up of Lockheed Martin , General Dynamics and Boeing , which has been in series production since 2002 as the F-22 Raptor . The YF-23 is also unofficially referred to as the Black Widow II after the first prototype , although the second machine was known internally as the Gray Ghost .
history
The "Advanced Tactical Fighter" program
The Tactical Air Command (TAC; German: Tactical Air Command) of the US Air Force funded the U.S. Air Force Tactical Forces 1985 Study (TAC-85) from 1969 to 1970 . The aim was to counter the improved capabilities of the Soviet Union's air forces . The result led to the deployment concept of the Advanced Tactical Fighter ( ATF, German : progressive tactical fighter aircraft) in 1971 . The concept was rather vague at the time; Around 1975 it was decided to build two prototypes for the period from 1977 to 1981. However, budget constraints led to the Lightweight Fighter Program, a design competition launched by the US Department of Defense in 1974 to find an inexpensive aircraft to replace some older types in the USAF's inventory. This resulted in the General Dynamics F-16 Fighting Falcon and the McDonnell Douglas F / A-18 Hornet .
In 1976 the first studies were started, which dealt with the use of stealth technology as part of the Advanced Tactical Fighter (ATF) concept . The ability to fly at supersonic speed without an afterburner was also considered important. In 1978 the USAF defined two different projects: the Enhanced Tactical Fighter (ETF) and the Advanced Tactical Attack System (ATAS). The technology for the ETF should be available in a short time, the ATAS was intended as a long-term goal. The focus was on air-to-ground capabilities, as the F-15 and F-16 were seen as sufficient for fighting Soviet warplanes. When the Soviet Union put the MiG-29 and MiG-31 from the manufacturer Mikoyan-Gurevich and the Su-27 from the manufacturer Sukhoi into service, the USAF changed its focus: the ETF was canceled and ATAS was referred to as ATF. As a multi- role fighter with STOL characteristics, it was intended to attack both air and ground targets.
In June 1981 the Aeronautic Systems Division (ASD) published a Request for Information (RFI) for an ATF concept, the RFI for the engine followed a month later. With Boeing , Fairchild , General Dynamics , Grumman , Lockheed , McDonnell Douglas , Northrop , Rockwell and Vought , nine companies applied for the construction of the airframe including the operating equipment and three engine manufacturers for the construction of the engine system . Over the next four years, the individual designs took shape. In the end, seven companies submitted their concepts. Each of the seven companies received $ 1 billion to deepen their concept further. The USAF was less interested in concrete plans; rather, the company's methods and technology should be developed to meet ATF requirements. In October 1982 the USAF also required a super cruising ability of Mach 1.5. NATO commanders were pessimistic about whether the military bases in Central Europe would survive a Soviet attack. Control of the airspace would then be carried out from air force bases in the Benelux countries or the United Kingdom . The ability to fly over enemy territory at supersonic speed throughout the mission without an afterburner should reduce vulnerability to enemy SAM positions and allow for a higher deployment rate. STOL properties with reverse thrust were also considered important to be able to operate from damaged airfields. In mid-1983, the ATF concept was realigned as an air superiority fighter . The range should be significantly greater than that of an F-15 with the same armament in order to be used from more distant bases. In order to avoid excessive costs, the USAF set a cost and weight limit. Also in 1983 the USAF dealt with the development of the engines , since negative experiences with the P&W F100 engine for the F-15 already existed in this area . General Electric and Pratt & Whitney received a $ 200 million contract in October of that year to design a suitable engine. Pratt & Whitney developed the XF119 based on the PW5000, while General Electric further developed the GE37 XF120, which was equipped with a variable bypass ratio ( English Variable Cycle Engine ).
Despite the same task, the companies developed different concepts based on the requirements and studies and developments they had already carried out. The USAF required a radar detection range of 240 °. Since the USAF itself conducted studies and came to the conclusion that stealth technology was now a necessity, the original Request for Information (RFI) was adapted to this a few months before the demonstration and validation phase. Originally, the designs were to be presented to the USAF in May 1985, and the best four designs were to receive $ 400 million each for the subsequent demonstration and validation phases to build prototypes. Due to the success of the Lightweight Fighter program, only two of the concepts should now enter the demonstration and validation phase, for which they would each receive 700 million US dollars. The USAF therefore recommended that the aviation industry form teams. They immediately started negotiations. In June 1986 Boeing, Lockheed and General Dynamics signed agreements, followed two months later by Northrop and McDonnell Douglas. Grumman and Rockwell remained independent and were later taken over by Northrop and Boeing, respectively. In October 1986, the Lockheed and Northrop teams received $ 691 million from the United States Department of Defense to design and construct the ATF prototypes, which were designated the YF-22 and YF-23.
Senior Sky
After the teams from Northrop and Lockheed received the ATF development contracts, the program continued under the code name Senior Sky . In private studies, Northrop found that a fighter jet with a low radar signature had the greatest chance of entering enemy airspace unnoticed. In conjunction with its own powerful radar, it should be able to shoot many opponents outside the pilot's range of vision ( Beyond Visual Range, BVR ) before they noticed his presence. Development of the YF-23 initially began as a 4-man team: chief engineer Bob Sandusky, his secretary, an aerodynamicist and an engineer for the structure. Various drafts were run through in order to find the best possible compromise with regard to the catalog of requirements.
Similar to its competitor Lockheed, Northrop came to the conclusion when assessing its various designs that none was able to meet all the requirements. First of all, this concerned the targeted weight limit. It proved impractical to design a 50,000 pound (22,680 kg) fighter aircraft that met all of the requirements. As a result, the USAF increased the weight limit. Second, the design turned out to be unsupervised . The USAF reacted to this by dropping the requirements for a thrust reverser in 1987 so that the design could be made more flexible. Thirdly, it turned out that an avionics package for a radar detection range of 240 ° would go beyond the intended scope of 9 million US dollars. In order to meet the budget of this item, the USAF reduced the required radar detection area and eliminated the IRST completely.
At that time, hundreds of people were working on the development of the YF-23. The cost of doing this was about $ 1 million a day. The stealth tests were carried out on a test site in the California desert. A model stood upside down on a mast in a hall with a capacity of over 28,000 m³, which hid the aircraft from spy satellites on the day . The effective radar reflection area was then examined at night using radar devices after the building hall, which was on rails, had been driven away. Because the measured radar cross-section resembled the appearance of a spider due to the shape of the wing edges, the nickname "Black Widow II" is said to have prevailed for this prototype.
In 1988 it was decided to build a total of 750 of these advanced tactical fighters (ATF) for the USAF, with a production rate of 72 aircraft per year. At the beginning of 1991 the winner was to be selected, the first production model was to be delivered in 1993 and put into service in 1996. Because the Defense Acquisition Board noted on October 6, 1988 that the development of the prototype had been delayed by six months, the ATF program was extended by one year. This postponed the end of the demonstration and validation phase until mid-1991. The first YF-23 PAV-1 (civil registration N231YF, USAF serial number 87-800) with Pratt & Whitney YF119 engines was dismantled in 1989 and covered under Guard transported to Edwards Air Force Base , California. On June 22, 1990, the first YF-23 was rolled out to invited guests. The second YF-23 PAV-2 (87-801) with General Electric YF120 engines followed on October 26.
Test program
At the beginning of the demonstration phase, Northrop's team was usually in front. The YF-23 took off on August 27, 1990 on its first 20-minute maiden flight . It was flown by Northrop's chief test pilot Paul Metz. Further flights took place in mid-September, during which supersonic speed was reached and the refueling capability with a KC-135 was demonstrated on September 14th. The aircraft behaved as predicted in the flight simulator. The super cruising ability was demonstrated on the fifth flight. Less than a month later, on September 29, the YF-22 also took off on its maiden flight with Lockheed's chief pilot Dave Furguson at the controls. Both machines were powered by the GE YF120. The second YF-22 took off on October 30th and flew for the first time with the P&W YF119. The first flight of the second YF-23 took place four days earlier, on October 26th. The only problem was the right main landing gear, which only engaged after repeated retraction and extension. Just a few weeks later, Lockheed's teams were also able to demonstrate the supercruise capability of their machines. With regard to flight characteristics, Lockheed placed great emphasis on maneuverability. In the following months, for example, some spectacular maneuvers were shown that no other aircraft could perform at that time, for example 360 ° rolls at an angle of attack of 60 °, which was due to the asymmetrically controlled 2D thrust vector nozzles . Meanwhile, the YF-23 demonstrated an official top speed of Mach 1.8 and achieved angles of attack of up to 25 °. Both machines were exposed to loads of up to 7 g during the test . Although both machines flew without on-board weapons and radar, Lockheed demonstrated the functionality of the launch systems for the AIM-9 and AIM-120 guided missiles, although this was not required by the Air Force. However, this still required concepts for design and production development during the testing phase, which were then submitted by the two teams on January 2, 1991.
On April 23, 1991, the Air Force finally announced the winner of the tender: the YF-22 "Lightning II" from Team Lockheed. The main factor behind this decision was the more advanced development and better maneuverability of the YF-22. Only she was able to fly in a controlled manner thanks to thrust vector control even after a stall, had a more developed cockpit and had demonstrated missile launches. The YF-23 had to struggle with the not fully developed weapon mounts. Pratt & Whitney won the engine competition with the more conservative YF119.
Whereabouts
Both YF-23s were then cannibalized and mothballed in a cordoned off area at Edwards Air Force Base . NASA planned to use one of the aircraft to test strain gauges , but it did not. The planes stood there for five years before being brought back to Hawthorne in 1995 by three Northrop Corporation enthusiasts . PAV-1 and PAV-2 were restored there and handed over to two museums:
- PAV-1 (Black Widow II) can be viewed today at the National Museum of the United States Air Force in Dayton . The aircraft is there in the “Research and Development” hangar.
- PAV-2 (Gray Ghost) was exhibited at the Western Museum of Flight in Hawthorne. In 2004 it was awarded to Northrop Grumman for exhibition purposes. The aircraft was then moved to its new location in the museum at Torrance Airport in California.
Rumors of a revival , according to which Northrop Grumman would have further developed the YF-23 as a fighter-bomber as a replacement or supplement for the F-15E Strike Eagle, are very unlikely, since the aircraft already had to struggle as a prototype with the not fully developed weapon mounts. Also in view of the obvious possibility of developing an FB-22 based on the F-22 Raptor , which would be more cost-effective.
technology
Airframe
The shape of the airframe was uncompromisingly optimized for stealth and speed. While the Lockheed F-117 initially forced the use of geometrically simple shapes in order to be able to calculate the reflections according to Huygens' principle, the increased computing power of the computer made it possible to continuously curve the surface. On this basis, Northrop developed the Tacit Blue stealth aircraft in the Assault Breaker program . Since Northrop had already developed the stealth bomber Senior Ice and was now working on Senior Sky, the findings of the "white whale" were also applied here. The front fuselage was equipped with chines in order to improve the steal properties and to increase the angle of attack through the formation of eddies (see strake ). Since the stealth properties against low-frequency radars strongly depend on the shape of the airframe, the machine was built as flat as possible. Radars from anti- aircraft positions always irradiate the aircraft from below, so an underbody that is as flat as possible is desirable. For this purpose, the engines and a large part of the fuselage are located above the fuselage-surface transition . In order to avoid corner reflectors between the rudder unit and the elevator, a V-tail unit with a 50 ° inclination was attached. While the YF-22 had a thrust vector control, which significantly increased maneuverability, the construction of the YF-23 placed more emphasis on shielding the infrared radiation. The outlet opening of the nozzles was therefore moved far forward, thus preventing direct observation of the hot nozzles from below. The engine exhaust was passed through troughs lined with tiles made of titanium aluminide . They were cooled by a labyrinth of air channels and holes, so that the temperature on the underside of the machine was below 150 ° C.
In order to achieve the highest possible supersonic speed, the hull was elongated and the area rule was applied consistently. The trapezoidal wings with a 40 ° leading edge sweep have a very small aspect ratio , which further reduces drag in supersonic flight. In contrast to the YF-22, which uses a pitot inlet, the air intake of the YF-23 is optimized for supersonic flight. During the supersonic flight, the incoming air in the air inlet must be slowed down to subsonic speed. In order to keep the total pressure loss and thus the loss of thrust as low as possible, as many oblique shock waves as possible should be used for braking. The placement of the inlets under the wings makes use of the inclined compression shock in supersonic flight, which descends at the leading edges. In order to keep the overflow resistance low when flying at high angles of attack, a ramp bleed system was installed as in the Eurofighter Typhoon . This is located between the leading edge of the wing and the air inlet and conveys the excess air to the top of the wing. In order to keep the loss of thrust when flying at high angles of slide as low as possible, the air inlets are designed a little deeper than the fuselage. The engine nozzles can be adjusted to the power using a movable upper lip.
Due to the elongated shape of the fuselage, together with the trapezoidal wings, there is a large moment of inertia around the transverse axis, which limits maneuverability. The choice of a V-tail unit is also unusual for a fighter aircraft, since the generation of pitching moments creates an unnecessarily high amount of air resistance, which greatly reduces the permanent turning rates compared to a conventional tail unit. The YF-23 is therefore not a classic air superiority fighter , but rather an interceptor . In order to keep the costs for the prototypes as low as possible, a modified main landing gear of the F-18 was used, the nose landing gear was taken over from the F-15.
Avionics
The cockpit of the YF-23 was taken over from the F-15C Eagle. The pilot sat on an ACES II ejector seat and steered the aircraft with a joystick between his feet. Nothing is known about the cockpit of a production version, but it should be similar to the glass cockpit of the YF-22.
As with Lockheed, avionics were based on the findings of the Pave Pillar program. It was investigated how integrated modular avionics (IMA) could be physically distributed over an aircraft in order to increase the damage tolerance in combat. The same structure of the computing modules can also save costs. As usual at IMA, the avionics system of the YF-23 was based on processing units that can take on any task within the data processing system. The processing units used a 32-bit GPPE (General Purpose Processing Element) from Unisys . The signal processing of the elements was carried out by a processor, which was located between two large slots with 75 cards each. The modules in the slots were designed redundantly to increase the damage tolerance. In contrast to Lockheed, there is no liquid cooling.
The prototypes did not have the AN / APG-77 radar or advanced electronics. However, Northrop and McDonnell Douglas built the entire avionics system and had it test-fly in a modified BAC 1-11 from Westinghouse.
Armament
In contrast to the YF-22, no weapon tests were carried out with the YF-23. Behind the nose landing gear, four radar-guided air-to-air missiles were supposed to be carried in an internal weapons bay to combat targets at long range. In addition to the already established AIM-120 AMRAAM , the Mach 4+ fast stealth guided missile Have Dash II , which was under development at the time, would also have come into question. There are different details about the carrying of four short-range weapons (at that time AIM-132 ASRAAM ). While on the one hand there is talk of an extended fuselage with more space for a further small gun bay behind the cockpit, on the other hand there is talk of side gun bays at the air inlets. An M61 Vulcan automatic cannon was to be installed on the upper starboard side at the level of the main weapon bay. The rather moderate armament for aerial battles out of sight of the pilot was probably one of the reasons for declaring the YF-22 the winner of the ATF competition.
Technical specifications
The official flight speed of the prototype YF-22/23 is stated to be unrealistically low. A Raptor, for example, has the same thrust as a YF-23 and roughly the same air resistance, but the official cruising and maximum speeds are far apart. The speed information in the table was therefore estimated from the values of the F-22 Raptor .
| Parameter | Data |
|---|---|
| Type: | Prototype for an air superiority fighter |
| Length: | 20.26 m |
| Wingspan: | 13.21 m |
| Wing area: | 87.80 m² |
| Wing extension : | 1.99 |
| Wing loading : |
|
| Height: | 4.20 m |
| Empty weight: | 16,783 kg |
| Normal takeoff weight: | 23,327 kg |
| Maximum take-off weight: | 29,029 kg |
| Fuel capacity: | 10,886 kg |
| g limits: | 7 g (prototype) |
| Top speed: |
|
| Marching speed: |
|
| Service ceiling: | 19,811 m |
| Use radius: |
|
| Engine: |
|
| Thrust-to-weight ratio : |
|
| Armament: | none (prototype) |
literature
- James C. Goodall: America's Stealth Fighters and Bombers, B-2, F-117, YF-22, and YF-23. MBI Publishing Company, St. Paul, Minnesota 1992, ISBN 0-87938-609-6 .
- Steve Pace: F-22 Raptor. McGraw-Hill, New York 1999, ISBN 0-07-134271-0 .
- Bill Sweetman: YF-22 and YF-23 Advanced Tactical Fighters. Motorbooks International Publishing, St. Paul, Minnesota 1991, ISBN 0-87938-505-7 .
Web links
- YF-23 Black Widow II on www.globalsecurity.org (English)
- The YF-23 Black Widow II at www.fas.org (English)
- Joe Baugher - Northrop / McDonnell Douglas YF-23 (English)
- Video (2:14)
Individual evidence
- ^ Gerhard Lang: paperback military jets. History, types, technology. GeraMond Verlag, Munich 2001, ISBN 978-3-7654-7220-6 , pp. 132-133.
- ↑ David C. Aronstein, Michael J. Hirschberg, Albert C. Piccirillo: Advanced tactical fighter to F-22 raptor. Origins of the 21st century air dominance fighter. American Institute of Aeronautics and Astronautics, Inc., Reston, Virginia, USA 1998, ISBN 1-56347-282-1 , p. 7 (English).
- ^ English: Concept of Operations (CONOPS) .
- ↑ Gerhard Siem: The great book of aircraft types. Civil & Military. 2nd Edition. Heel Verlag, Königswinter 2015, ISBN 978-3-86852-709-4 , p. 211. Page 211 is devoted to the Northrop YF-23 “Black Widow II” aircraft type.
- ^ YF-23 page NASA Dryden Flight Research Center, January 20, 1996.
- ↑ Popular Science April 1991 - Supercruisers