YF-23 Black widow II

 The Northrop/McDonnell Douglas YF-23 was a prototype fighter aircraft designed for the United States Air Force. The YF-23 was a finalist in the U.S. Air Force's Advanced Tactical Fighter competition. Two YF-23s were built and were nicknamed "Black Widow II" and "Gray Ghost", respectively. The YF-23 lost the contest to the Lockheed YF-22, which entered production as the Lockheed Martin F-22 Raptor.

 

Design and development

The YF-22 and YF-23 were competing in the USAF's Advanced Tactical Fighter (ATF) program, conceived in the early 1980s, to provide a replacement for the F-15 Eagle. Contracts for the two most promising designs were awarded in 1986.
The YF-23 was designed to meet USAF requirements for survivability, supersonic cruise (supercruise), stealth, and ease of maintenance. Designed with all-aspect stealth as a high priority, Northrop drew on the company's experience with the B-2 Spirit and F/A-18 Hornet. The YF-23 was an unconventional-looking aircraft with trapezoidal wings, substantial area-ruling, and a V-tail.Similar to the B-2, the exhaust from the YF-23's engines flows through troughs lined with heat ablating tiles, which shields the exhaust from infrared (IR) missile detection from below. The vehicle management system coordinates movements of the control surfaces for maneuvers and for stable flight, along with other aircraft functions.The wing flaps and ailerons deflect inversely on either side to provide roll. Pitch was provided by movement of both V-tails, and yaw was supplied by opposite movement. Deflecting the wing flaps down and ailerons up on both sides simultaneously provided for aerodynamic braking.
Although possessing an advanced design, in order to reduce costs and development, a number of F-15 Eagle components were utilized including the standard F-15 nose wheel unit and the forward cockpit of the F-15E Strike Eagle. Two aircraft were built. YF-23 #1 (PAV-1) was fitted with Pratt & Whitney YF119 engines, while YF-23 #2 (PAV-2) was fitted with General Electric YF120 engines. The YF-23 featured fixed nozzles. The first YF-23 was rolled out on 22 June 1990, and first flew on 27 August 1990. YF-23 #2 first flew on 26 October 1990^.
The black YF-23 (PAV-1) was nicknamed "Black Widow II", after the Northrop P-61 Black Widow of World War II and had a red hourglass marking resembling the underbelly marking of the black widow spider. The black widow marking was briefly seen under PAV-1 before being removed at the insistence of Northrop management. The gray colored YF-23 (PAV-2) was nicknamed "Gray Ghost".

Operational history

Evaluation

Both YF-23s were furnished in the configuration specified before the requirement for thrust reversing was dropped. The weapons bay was configured for weapons launch but no missiles were fired, unlike Lockheed's demonstration aircraft. The YF-23s flew 50 times for a total of 65.2 hours. The first YF-23 with P&W engines supercruised at Mach 1.43 on 18 September 1990 and the second YF-23 with GE engines reached Mach 1.6 on 29 November 1990. For comparison, the YF-22 achieved Mach 1.58 in supercruise. The flight testing demonstrated Northrop's predicted performance values for the YF-23.
The YF-22 won the competition in April 1991. The YF-23 design was more stealthy and faster, but the YF-22 was more agile. It has been speculated in the aviation press that the YF-22 was also seen as more adaptable to the Navy's Navalized Advanced Tactical Fighter (NATF), though as it turned out the US Navy abandoned NATF a few months later.
After losing the competition, both YF-23s were transferred to NASA's Dryden Flight Research Center, at Edwards AFB, California without the engines. NASA planned to use one of the aircraft to study strain gauge loads calibration techniques, but this did not occur.

Possible revival

In late 2004, Northrop Grumman proposed a YF-23 based design for the USAF's interim bomber requirement, a role for which the FB-22 and B-1R are also competing. Aircraft PAV-2 was modified by Northrop as a full size model of its proposed interim bomber. The interim bomber requirement has since been canceled in favor of a more long-term, bomber replacement requirement. The same YF-23-derived design could possibly be adapted to fulfill this role as well. However, it appears the possibility of a YF-23-based interim bomber was ended with the 2006 Quadrennial Defense Review, in lieu of a long range bomber with a much greater range.

Su-47 Berkut

The Sukhoi Su-47 Berkut (Russian: Су-47 Беркут - Golden Eagle) (NATO reporting name Firkin), also designated S-32 and S-37 (not to be confused with Su-37) during initial development, is an experimental supersonic jet fighter developed by Sukhoi Aviation Corporation. A distinguishing feature of the aircraft is its forward-swept wing, similar to that of the Tsybin's LL-3. The sole aircraft produced is an advanced technology demonstrator prototype and manufacture of a planned second flying prototype is under question due to recent MiG developments of 5th generation Jet fighters. This aircraft is sometimes confused with the single-engined delta canard design offered by Sukhoi in the early 1990s under the S-37 designation.

Development

Originally known as the S-37, Sukhoi redesignated its advanced test aircraft as the Su-47 in 2002. Officially nicknamed Berkut (Golden Eagle), the Su-47 was originally built as Russia's principal testbed for composite materials and sophisticated fly-by-wire control systems.
TsAGI has long been aware of the advantages of forward-swept wings, with research including the development of the Tsibin LL and study of the captured Junkers Ju 287 in the 1940s. Forward-swept wings yield a higher maximum lift coefficient, reduced bending moments, and delayed stall when compared to more traditional wing shapes. At high angles of attack, the wing tips remain unstalled allowing the aircraft to retain aileron control. Conversely, forward sweep geometrically creates increased angle of incidence of the outer wing sections when the wing bends under load. This creates more lift, more load, more angle of incidence, etc. This leads to a tendency to for the wings to fail structurally at lower speeds than for a straight or aft-swept wing. Forward swept wings counter this by being designed to twist downward as they bend upward. This twisting-as-it-bends is done with composite materials on the S-37, but it can also be done with conventional materials.
The project was launched in 1983 on order from the Soviet Air Force. But when the USSR dissolved, funding was frozen and development continued only through funding by Sukhoi. Like its US counterpart, the Grumman X-29, the Su-47 is primarily a technology demonstrator for future Russian fighters. However, Sukhoi is now attempting to market the Su-47 to the Russian military and foreign customers as a production fighter in its own right.

Design

Outline of the Sukhoi Su-47

The Su-47 is of similar dimensions to previous large Sukhoi fighters, such as the Su-35. To reduce development costs, the Su-47 borrowed the forward fuselage, vertical tails, and landing gear of the Su-27 family. Nonetheless, the aircraft includes reduced radar signature features (including radar absorbent materials), an internal weapons bay, and space set aside for an advanced radar. Though similar in overall concept to the American X-29 research aircraft of the 1980s, the Su-47 is about twice the size and far closer to an actual combat aircraft than the US design.
To solve the problem of wing-twisting, the Su-47 makes use of composite materials carefully tailored to resist twisting while still allowing the wing to bend for improved aerodynamic behavior. Due to its comparatively large wingspan the Su-47 is to be equipped with folding wings in order to fit inside Russian hangars.
Like its immediate predecessor, the Su-37, the Su-47 is of tandem-triple layout, with canards ahead of wings and tailplanes. Interestingly, the Su-47 has two tailbooms of unequal length outboard of the exhaust nozzles. The shorter boom, on the left-hand side, houses rear-facing radar, while the longer boom houses a brake parachute.

Maneuverability

The Su-47 has extremely high agility at subsonic speeds, enabling the aircraft to alter its angle of attack and its flight path very quickly while retaining maneuverability in supersonic flight. The Su-47 has a maximum speed of Mach 1.6 at high altitudes and a 9g capability.
Maximum turn rates, and the upper and lower limits on airspeed for weapon launch, are important criteria in terms of combat superiority. The Su-47 aircraft has very high levels of maneuverability with maintained stability and controllability at extreme angles of attack. Maximum turn rates are important in close combat and also at medium and long range, when the mission may involve engaging consecutive targets in different sectors of the airspace. A high turn rate of the Su-47 allows the pilot to turn the fighter aircraft quickly towards the next target to initiate the weapon launch. Like most other fighters with fly by wire controls, the Su-47 achieves some of its high maneuverability through relaxed stability.
The swept-forward wing, compared to a swept-back wing of the same area, provides a number of advantages:

• higher lift-to-drag ratio
• higher capacity in dogfight maneuvers
• higher range at subsonic speed
• improved stall resistance and anti-spin characteristics
• improved stability at high angles of attack
• a lower minimum flight speed
• a shorter take-off and landing distance

 Fuselage

The Su-47s fuselage is oval in cross section and the airframe is constructed mainly of aluminium and titanium alloys and 13% (by weight) of composite materials. The nose radome is slightly flattened at the fore section, and has a horizontal edge to optimise the aircraft's anti-spin characteristics.

 Wings

The forward-swept midwing gives the unconventional (and characteristic) appearance of the Su-47, earning it the nickname of 'devil' and 'slingshot'. A substantial part of the lift generated by the forward-swept wing occurs at the inner portion of the wingspan. The lift is not restricted by wingtip stall. The ailerons - the wing's control surfaces - remain effective at the highest angles of attack, and controllability of the aircraft is retained even in the event of airflow separating from the remainder of the wings' surface.
The wing panels are constructed of nearly 90% composites. The forward-swept midwing has a high aspect ratio, which contributes to long-range performance. The leading-edge root extensions blend smoothly to the wing panels, which are fitted with deflectable slats on the leading edge; flaps and ailerons on the trailing edge. The all-moving and small-area trapezoidal canards are connected to the leading-edge root extensions.
A downside of such a forward-swept wing design is that it geometrically produces wing twisting as it bends under load, resulting in greater stress on the wing than for a similar straight or aft-swept wing. This requires the wing be designed to twist as it bends - opposite to the geometric twisting. This is done by the use of composites wing skins layed-up to twist. Despite this, the plane was initially limited to Mach 1.6. Recent engineering modifications have raised this limit, but the new limit has not been specified.

 Thrust vectoring

The thrust vectoring (with PFU engine modification) of ±20° at 30°/second in pitch and yaw will greatly support the agility gained by other aspects of the design.

Cockpit

The cockpit's design has focused on maintaining a high degree of comfort for the pilot and also on the pilot being able to control the aircraft in extremely high g-load maneuvers. The aircraft is equipped with a new ejection seat and life support system. The variable geometry adaptive ejection seat is inclined at an angle of 60°, which reduces the impact of high g forces on the pilot. The seat allows dogfight and missile avoidance maneuvers with significantly higher g loadings than can normally be tolerable. The Su-47 pilot uses a side-mounted, low-travel control stick and a tensiometric throttle control. Pilots, however, claim that the cockpit gives them low visibility due to poor design. This reclined seating arrangement was first used in the American F-16.

F-22 "Raptor"

The Lockheed Martin/Boeing F-22 Raptor is a single-seat, twin-engine fifth-generation fighter aircraft that uses stealth technology. It was designed primarily as an air superiority fighter, but has additional capabilities that include ground attack, electronic warfare, and signals intelligence roles. Lockheed Martin Aeronautics is the prime contractor and is responsible for the majority of the airframe, weapon systems and final assembly of the F-22. Program partner Boeing Defense, Space & Security provides the wings, aft fuselage, avionics integration, and all of the pilot and maintenance training systems.
The aircraft was variously designated F-22 and F/A-22 during the years prior to formally entering USAF service in December 2005 as the F-22A. Despite a protracted and costly development period, the United States Air Force considers the F-22 a critical component for the future of US tactical air power, and claims that the aircraft is unmatched by any known or projected fighter, while Lockheed Martin claims that the Raptor's combination of stealth, speed, agility, precision and situational awareness, combined with air-to-air and air-to-ground combat capabilities, makes it the best overall fighter in the world today. Air Chief Marshal Angus Houston, Chief of the Australian Defence Force, said in 2004 that the "F-22 will be the most outstanding fighter plane ever built."
The high cost of the aircraft, a lack of clear air-to-air combat missions because of the lengthy delays in the Russian and Chinese fifth generation fighter programs, a US ban on Raptor exports, and the development of the cheaper and more versatile F-35 resulted in calls to end F-22 production. In April 2009 the US Department of Defense proposed to cease placing new orders, subject to Congressional approval, for a final procurement tally of 187 Raptors. The US Senate and House each passed 2010 budget bill versions without F-22 production funding in July 2009. Congress worked to combine these versions into one bill,  signed the National Defense Authorization Act for Fiscal Year 2010 in October 2009, without funding for F-22 production.

5th Generation Fighter Aircraft

                                                                   

 

The fifth generation was ushered in by the Lockheed Martin/Boeing F-22 Raptor in late 2005. Currently the cutting edge of fighter design, fifth-generation fighters are characterized by being designed from the start to operate in a network-centric combat environment, and to feature extremely low, all-aspect, multi-spectral signatures employing advanced materials and shaping techniques. They have multifunction AESA radars with high-bandwidth, low-probability of intercept (LPI) data transmission capabilities. The Infra-red search and track sensors incorporated for air-to-air combat as well as for air-to-ground weapons delivery in the 4.5th generation fighters are now fused in with other sensors for Situational Awareness IRST or SAIRST, which constantly tracks all targets of interest around the aircraft so the pilot need not guess when he glances. These sensors, along with advanced avionics, glass cockpits, helmet-mounted sights (not currently on F-22), and improved secure, jamming-resistant LPI datalinks are highly integrated to provide multi-platform, multi-sensor data fusion for vastly improved situational awareness while easing the pilot's workload. Avionics suites rely on extensive use of very high-speed integrated circuit (VHSIC) technology, common modules, and high-speed data buses. Overall, the integration of all these elements is claimed to provide fifth-generation fighters with a "first-look, first-shot, first-kill capability".
The AESA radar offers unique capabilities for fighters (and it is also quickly becoming a sine qua non for Generation 4.5 aircraft designs, as well as being retrofitted onto some fourth-generation aircraft). In addition to its high resistance to ECM and LPI features, it enables the fighter to function as a sort of "mini-AWACS," providing high-gain electronic support measures (ESM) and electronic warfare (EW) jamming functions.