The Northrop Grumman E-2 Hawkeye is an American all-weather, carrier-capable, tactical airborne early warning (AEW) aircraft. This twin-turboprop aircraft was designed and developed during the late 1950s and early 1960s by the Grumman Aircraft Company for the United States Navy as a replacement for the earlier, piston-engined E-1 Tracer, which was rapidly becoming obsolete. The aircraft's performance has been upgraded with the E-2B and E-2C versions, where most of the changes were made to the radar and radio communications due to advances in electronic integrated circuits and other electronics.
The fourth major version of the Hawkeye is the E-2D, which first flew in 2007. The E-2 was the first aircraft designed specifically for AEW, as opposed to a modification of an existing airframe, such as the Boeing E-3 Sentry. Variants of the Hawkeye have been in continuous production since 1960, giving it the longest production run of any carrier-based aircraft.
The E-2 received the nickname "Super Fudd"Koppmann, George C., Carrier Airborne Early Warning. George C. Koppmann (LT, USNR – inactive) home page. Retrieved: 13 December 2006. because it replaced the WF (later E-1) "Willy Fudd". In recent decades, the E-2 has been commonly referred to as the "Hummer" because of the distinctive sounds of its turboprop engines, quite unlike those of turbojet and turbofan jet engines. In addition to U.S. Navy (USN) service, smaller numbers of E-2s have been sold to the armed forces of Egypt, France, Israel, Japan, Mexico, Singapore, and Taiwan. Grumman also used the basic layout of the E-2 to produce the Grumman C-2 Greyhound cargo aircraft.
Development
Background Continual improvements in airborne radars to 1956 led to the construction of AEW airplanes by several different countries and several different armed forces. The functions of command and control and sea and air surveillance were also added. The first carrier-based aircraft to perform these missions for the USN and its allies was the Douglas AD Skyraider. It was replaced in USN service by the Grumman E-1 Tracer, which was a modified version of the S-2 Tracker twin-engined, antisubmarine warfare aircraft, where the radar was carried in an aerofoil-shaped radome carried above the aircraft's fuselage.Godfrey 1977, pp. 7–8.
E-2A and E-2B Hawkeye In 1956, the USN developed a requirement for an AEW aircraft where its data could be integrated into the Naval Tactical Data System aboard the its ships, with a design from Grumman being selected to meet this requirement in March 1957.Swanborough and Bowers 1976, p. 244. Its design, initially designated W2F-1, but later redesignated the E-2A Hawkeye, was the first carrier plane that had been designed from its wheels up as an AEW and command-and-control airplane. The design engineers at Grumman faced immense challenges, including the requirement that the aircraft be able to operate from the older modified s. These vessels were built during World War II and were smaller than modern carriers, being later modified to allow them to operate jet aircraft. Consequently, height, weight, and length restrictions had to be factored into the E-2A design, resulting in some handling characteristics that were less than ideal. However, the E-2A never operated from the modified Essex-class carriers.
The first prototype, acting as an aerodynamic testbed only, flew on 21 October 1960. The first fully equipped aircraft followed it on 19 April 1961 and entered service with the USN as the E-2A in January 1964.Taylor 1976, p. 291. By 1965, the project had accumulated so many development issues that it was cancelled after 59 aircraft had already been built. In particular, difficulties were being experienced due to inadequate cooling in the closely packed avionics compartment. Early computers and complex avionics systems generated considerable heat and could fail without proper ventilation. These issues continued long after the aircraft entered service. At one point, reliability was so bad that the entire fleet of aircraft was grounded.
After Navy officials had been forced to explain to Congress why four production contracts had been signed before avionics testing had been completed, action was taken; Grumman and the USN scrambled to improve the design. The unreliable rotary drum computer was replaced by a Litton L-304 digital computer Alt URL and various avionics systems were replaced – the upgraded aircraft were designated E-2Bs. In total, 49 of the 59 E-2As were upgraded to E-2B standards. These aircraft replaced the E-1B Tracers in the various USN AEW squadrons.
E-2C Hawkeye and upgrades
Although the upgraded E-2B was a vast improvement on the unreliable E-2A, it was an interim measure. The USN knew the design had much greater capability and had yet to achieve the performance and reliability parameters set out in the original 1957 design. In April 1968, a reliability improvement program was initiated. Now that the capabilities of the aircraft were starting to be realized, more were desired; 28 new E-2Cs were ordered to augment the 49 E-2Bs that would be upgraded. Improvements in the new and upgraded aircraft were concentrated in the radar and computer performance.
Two E-2A test machines were modified as E-2C prototypes, the first flying on 20 January 1971. Trials proved satisfactory, and the E-2C was ordered into production. The first production aircraft performed its initial flight on 23 September 1972. The original E-2C, known as Group 0, consisted of 55 aircraft; the first aircraft became operational in 1973 and began serving on carriers in the 1980s and '90s, until they were replaced in first-line service by Group II aircraft. The US Naval Reserve used some aircraft for tracking drug smugglers. The E-2C was commonly used in conjunction with Grumman F-14 Tomcat fighters, monitoring airspace, then vectoring Tomcats over the Link-4A datalink to destroy potential threats with AIM-9 Sidewinder, AIM-7 Sparrow, and most notably the long-range AIM-54C Phoenix missiles.
The next production run, between 1988 and 1991, had 18 aircraft built to the Group I standard, which replaced the E-2's older APS-125 radar and T56-A-425 turboprops with their successors, the APS-139 radar system and T56-A-427 turboprops. The first Group I aircraft entered service in August 1981. Upgrading the Group 0 aircraft to Group I specifications was considered, but the cost was comparable to a new production aircraft, so upgrades were not conducted. Group I aircraft were only flown by the Atlantic Fleet squadrons. This version was followed within a few years by the Group II, which had the improved APS-145 radar. Fifty Group II aircraft were delivered, with 12 being upgraded Group I aircraft. This new version entered service in June 1992 and served with the Pacific and Atlantic Fleet squadrons.
By 1997, the USN intended that all front-line squadrons would be equipped, for a total of 75 Group II aircraft. Grumman merged with Northrop in 1994 and plans began on the Group II Plus, also known as the Group II/NAV upgrade. This kept the same computer and radar as the Group II, while upgrading the pilot avionics, such as replacing the mechanical inertial navigation system (INS) with a more reliable and accurate laser ring gyroscope-driven INS, installing dual multifunction control display units (vs. one in the Group II) and integrating GPS into the weapons system. A variant of the Group II with upgrades to the mission computer and combat information center (CIC) workstations is referred to as the MCU/ACIS; these were produced in small numbers due to production of the Hawkeye 2000 soon after its introduction. All Group II aircraft had their 1960s-vintage computer processors replaced by a mission computer with the same functionality via modern computer technology, referred to as the Group II Mission Computer Replacement Program (GrIIM RePr, pronounced "grim reaper").
Another upgrade to the Group II was the Hawkeye 2000, which featured the same APS-145 radar, but incorporated an upgraded mission computer and CIC workstations (Advanced Control Indicator Set) and carries the USN's new cooperative engagement capability (CEC) data-link system. It is also fitted with larger-capacity, vapor-cycle, avionics cooling system. Starting in 2007, a hardware and software upgrade package began to be added to existing Hawkeye 2000 aircraft. This upgrade allowed faster processing, double-current trackfile capacity, and access to satellite information networks. Hawkeye 2000 cockpits being upgraded included solid-state glass displays and a GPS-approach capability. The remaining Hawkeye Group II NAV Upgrade aircraft received GPS approach capability, but did not get the solid-state glass displays.
In 2004, the E-2C's propeller system was changed; a new eight-bladed propeller (prop) system named NP2000 was developed by the Hamilton-Sundstrand company to replace the old four-bladed design. Improvements included reduced vibrations and better maintainability as a result of the ability to remove prop blades individually instead of having to remove the entire prop and hub assembly. The prop blades are of carbon fiber construction with steel leading-edge inserts and deicing boots at the root of the blade.
E-2D Advanced Hawkeye
The E-2 was once considered for replacement by the "Common Support Aircraft", but this concept was abandoned. The latest E-2 version is the E-2D Advanced Hawkeye, which features an entirely new avionics suite, including the new AN/APY-9 radar, radio suite, mission computer, integrated satellite communications, flight-management system, improved T56-A-427A engines, a glass cockpit, and aerial refueling. The APY-9 radar features an active electronically scanned array, which adds electronic scanning to the mechanical rotation of the radar in its radome. The E-2D includes provisions for the copilot to act as a "tactical fourth operator", able to reconfigure the main cockpit display to show radar, IFF, and Link 16 (JTIDS) or CEC and to access all acquired data. The E-2D's first flight occurred in August 2007."Northrop Grumman E-2D Advanced Hawkeye Completes First Flight" . Northrop Grumman, 3 August 2007.
In May 2009, an E-2D used its CEC system to engage an overland cruise missile with a Standard Missile SM-6 fired from another platform in an integrated fire-control system test. These two systems were to form the basis of the Naval Integrated Fire Control – Counter Air (NIFC-CA) when fielded in 2015; the USN is investigating adding other systems to the NIFC-CA network in the future.
The APY-9 radar has been suspected of being capable of detecting fighter-sized stealth aircraft, which are typically optimized against high frequencies such as Ka, Ku, X, C, and parts of the S-bands. Small aircraft lack the size or weight allowances for all-spectrum, low-observable features, leaving a vulnerability to detection by the UHF-band APY-9 radar, potentially detecting fifth-generation fighters including the Russian Sukhoi Su-57 and the Chinese Chengdu J-20 and Shenyang J-31. Historically, UHF radars had resolution and detection issues that made them ineffective for accurate targeting and fire control; Northrop Grumman and Lockheed claim that the APY-9 has solved these shortcomings by using advanced electronic scanning and high digital computing power via space/time adaptive processing. According to the USN's NIFC-CA concept, the E-2D could guide fleet weapons, such as AIM-120 AMRAAM and SM-6 missiles, onto targets beyond a launch platform's detection range or capabilities.The U.S. Navy's Secret Counter-Stealth Weapon Could Be Hiding in Plain Sight – News.USNI.org, 9 June 2014