Editing Grumman E-2 Hawkeye (section)

==Development==
{{More citations needed section|date=January 2013}}

===Background===
Continual improvements in airborne radars through 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 U.S. Navy and its allies was the [[Douglas A-1 Skyraider|Douglas AD Skyraider]], which was replaced in US Navy service by the [[Grumman E-1 Tracer]], which was a modified version of the [[S-2 Tracker]] twin-engine [[anti-submarine warfare]] aircraft, where the radar was carried in an aerofoil-shaped radome carried above the aircraft's fuselage.<ref name="Godfrey p7-8">Godfrey 1977, pp. 7–8.</ref>

===E-2A and E-2B Hawkeye===
In 1956, the U.S. Navy developed a requirement for an airborne early warning aircraft where its data could be integrated into the [[Naval Tactical Data System]] aboard the Navy's ships, with a design from Grumman being selected to meet this requirement in March 1957.<ref name="Swan Navyp244">Swanborough and Bowers 1976, p. 244.</ref> 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 {{sclass|Essex|aircraft carrier|1}}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, various height, weight and length restrictions had to be factored into the E-2A design, resulting in some handling characteristics which were less than ideal. However, the E-2A never operated from the modified Essex class carriers.

[[File:Grumman E-2A Hawkeye in flight in the early 1960s.jpg|thumb|left|A Grumman E-2A Hawkeye in flight in the early 1960s]]
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 US Navy as the E-2A in January 1964.<ref name="JAWA76 p291">Taylor 1976, p. 291.</ref> 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.{{Citation needed|date=August 2018}}

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 US Navy scrambled to improve the design. The unreliable rotary drum computer was replaced by a [[Litton Industries|Litton]] L-304 digital computer<ref>{{cite journal |title=across the editor's desk: COMPUTING AND DATA PROCESSING NEWSLETTER - LITTON'S L-304 |journal=Computers and Automation |date=Oct 1965 |volume=14 |issue=10 |pages=43–44 |url=https://archive.org/details/bitsavers_computersA_7957328/page/n41?q=%22monolithic+silicon+integrated+and+hybrid%22}}
*{{cite journal|title=COMPUTERS AND DATA PROCESSORS, NORTH AMERICA: 4. Litton Industries, Guidance and Control Systems Division, L-304 Militarized Computer, Woodland Hills, California|journal=Digital Computer Newsletter|date=Jan 1966|volume=18|issue=1|page=23|url=http://www.dtic.mil/docs/citations/AD0694647|language=en|access-date=February 25, 2019|archive-url=https://web.archive.org/web/20180603105832/http://www.dtic.mil/docs/citations/AD0694647|archive-date=June 3, 2018|url-status=dead}}</ref><ref>{{cite web|url=https://archive.org/details/bitsavers_littonL304mputerSystemSep66_6953238/page/n7|title=The Litton L-304 Dual Computer System|date=1966|work=trailing-edge.com|page=2|access-date=August 1, 2016|quote=L-304E with 4096 words of memory was completed and put in operation. Very shortly thereafter, the computer was tied to a typewriter, paper tape reader and punch, a small magnetic tape, a real-time clock and a small CRT display and control console.}} [http://bitsavers.trailing-edge.com/pdf/litton/L-304/The_Litton_L-304_Dual_Computer_System_Sep66.pdf Alt URL]
* {{cite journal|date=Dec 1967|title=1967 Pictorial Report on the Computer Field: DIGITAL COMPUTERS - TACTICAL AUTOMATIC DATA PROCESSING SYSTEM (TADPS)|url=https://archive.org/details/bitsavers_computersA_11280381/page/n33?q=%22TACTICAL+AUTOMATIC+DATA+PROCESSING+SYSTEM+%28TADPS%29%22|journal=Computers and Automation|issue=12|page=35}}</ref> 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 standard. These aircraft replaced the E-1B Tracers in the various US Navy AEW squadrons.{{cn|date=January 2024}}

===E-2C Hawkeye and upgrades===
[[File:US Navy 090713-N-2798I-005 An E-2C Hawkeye assigned to the Greyhawks of Carrier Airborne Early Warning Squadron (VAW) 120 flies over Jacksonville, Fla.jpg|thumb|An E-2C Hawkeye assigned to [[VAW-120]] flies over Jacksonville, Florida]]
[[File:US Navy 081111-N-9565D-040 t. Brett Whorley, left, and Lt. Andrew Leatherwood, assigned to Airborne Early Warning Squadron (VAW) 115, the.jpg|thumb|Radar operations inside an E-2C of [[VAW-115]]]]
[[File:USS Theodore Roosevelt (CVN 71) conducts flight operations. (49122248696).jpg|thumb|An E-2C Hawkeye takes off from the {{USS|Theodore Roosevelt|CVN-71}} in 2019]]

Although the upgraded E-2B was a vast improvement on the unreliable E-2A, it was an interim measure. The US Navy 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. In addition, 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.{{Citation needed|date=August 2015}}

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 serving on carriers in the 1980s and 1990s, until they were replaced in first-line service by Group II aircraft. US Navy Reserve used some aircraft for tracking drug smugglers. The type was commonly used in conjunction with [[Grumman F-14 Tomcat]] fighters, monitoring airspace and then vectoring Tomcats over the [[Link 4|Link-4A]] datalink to destroy potential threats with long range [[AIM-54|AIM-54C Phoenix]] missiles.{{Citation needed|date=August 2015}}

The next production run, between 1988 and 1991, saw 18 aircraft built to the Group I standard. Group I aircraft 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.  A total of 50 Group II aircraft were delivered, 12 being upgraded Group I aircraft. This new version entered service in June 1992 and served with the Pacific and Atlantic Fleet squadrons.{{Citation needed|date=August 2015}}

By 1997, the US Navy 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 (MFCDUs) (vice one in the Group II) and integrating GPS into the weapon system. A variant of the Group II with upgrades to the mission computer and 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 GrIIM RePr (Group II Mission Computer Replacement Program, pronounced "grim reaper").<ref>{{cite web|url=http://www.navy.mil/submit/display.asp?story_id=15443|title=E-2C New Mission Computer Improves Reliability, Reduces Costs|first=This story was written by Program Executive Office for Tactical Aircraft Programs Public|last=Affairs|work=navy.mil|access-date=August 1, 2016|archive-url=https://web.archive.org/web/20161011010842/http://www.navy.mil/submit/display.asp?story_id=15443|archive-date=October 11, 2016|url-status=dead}}</ref>

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 ([[Combat Information Center]]) workstations (Advanced Control Indicator Set or ACIS and carries the U.S. Navy's new CEC (cooperative engagement capability) [[data link|data-link system]]. It is also fitted with a 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 allows faster processing, double current trackfile capacity and access to satellite information networks. Hawkeye 2000 cockpits being upgraded include solid-state glass displays and a GPS-approach capability.<ref>{{cite web |title=Northrop Grumman E-2C Hawkeye 2000 |url=http://www.northropgrumman.com/Capabilities/E2CHawkeye2000/Documents/pageDocuments/E-2C_Hawkeye_2000_data_sheet.pdf |url-status=live |archive-url=https://web.archive.org/web/20141027231614/http://www.northropgrumman.com/Capabilities/E2CHawkeye2000/Documents/pageDocuments/E-2C_Hawkeye_2000_data_sheet.pdf |archive-date=October 27, 2014 |access-date=July 14, 2013}}</ref> The remaining Hawkeye Group II NAV Upgrade aircraft received GPS approach capability, but did not get the solid-state glass displays.{{Citation needed|date=August 2015}}

In 2004, the E-2C's propeller system was changed; a new eight-bladed propeller system named NP2000 was developed by the [[Hamilton Sundstrand|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.<ref>{{cite web|url=http://www.navy.mil/submit/display.asp?story_id=11296|title=Navy's NP2000 Propeller Completes Flight Testing|first=This story was written by Denise Deon Wilson, NAVAIR Public Affairs|last=PEO(T)|work=navy.mil|access-date=August 1, 2016|archive-url=https://web.archive.org/web/20161011005226/http://www.navy.mil/submit/display.asp?story_id=11296|archive-date=October 11, 2016|url-status=dead}}</ref> The propeller blades are of carbon fiber construction with steel leading edge inserts and de-icing boots at the root of the blade.<ref>{{cite web|url=http://utcaerospacesystems.com/cap/systems/Pages/propeller-systems-business.aspx|title=Aircraft Propeller Systems – UTC Aerospace Systems|work=utcaerospacesystems.com|access-date=August 1, 2016|archive-url=https://web.archive.org/web/20160802193636/http://utcaerospacesystems.com/cap/systems/Pages/propeller-systems-business.aspx|archive-date=August 2, 2016|url-status=live}}</ref>

===E-2D Advanced Hawkeye===
[[File:An E-2D Hawkeye flies over Naval Base Norfolk (13315193084).jpg|thumb|E-2D of [[VAW-125]] over [[Naval Station Norfolk|NS Norfolk]]]]

Once considered for replacement by the "[[Common Support Aircraft]]", 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 {{anchor|AN/APY-9}}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]].<ref>{{cite news |last=Majumdar |first=Dave |date=2014-10-16 |title=Navy Declares IOC For E-2D Advanced Hawkeye |url=http://news.usni.org/2014/10/16/navy-declares-ioc-e-2d-advanced-hawkeye |work=US Naval Institute |access-date=2015-07-25 |archive-url=https://web.archive.org/web/20150724120529/http://news.usni.org/2014/10/16/navy-declares-ioc-e-2d-advanced-hawkeye |archive-date=July 24, 2015 |url-status=dead }}</ref><ref>{{cite web|url=https://www.northropgrumman.com/what-we-do/air/e-2d-advanced-hawkeye/ |title=E-2D Advanced Hawkeye |publisher=Northrop Grumman |date= |accessdate=2022-05-02}}</ref> The APY-9 radar features an [[active electronically scanned array]] (AESA),<ref name="Jennings">{{cite web|url=https://www.janes.com/defence-news/news-detail/us-approves-e-2ds-for-france|title=US approves E-2Ds for France|last=Jennings|first=Gareth|work=Janes.com|date=July 7, 2020 |publisher=Janes|access-date=29 March 2022}}</ref> 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 4th Operator" (T4O), who can reconfigure his main cockpit display to show [[radar]], [[Identification friend or foe|IFF]], [[Link 16|Link 16 (JTIDS)]]/CEC and access all acquired data. The E-2D's first flight occurred on 3 August 2007.<ref>[http://www.irconnect.com/noc/press/pages/news_releases.html?d=124332 "Northrop Grumman E-2D Advanced Hawkeye Completes First Flight"] {{webarchive|url=https://web.archive.org/web/20070927180030/http://www.irconnect.com/noc/press/pages/news_releases.html?d=124332 |date=September 27, 2007}}. Northrop Grumman, 3 August 2007.</ref> On 8 May 2009, an E-2D used its [[Cooperative Engagement Capability]] system to engage an overland cruise missile with a [[RIM-174 Standard ERAM|Standard Missile SM-6]] fired from another platform in an integrated [[fire-control system]] test.{{cn|date=January 2024}} These two systems will 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.<ref>{{cite news |url=http://www.dodbuzz.com/2014/05/22/navy-considers-its-beyond-the-horizon-future/ |title=Navy Considers it's Beyond-the-Horizon Future |last1=Osborn |first1=Kris |date=22 May 2014 |website=www.dodbuzz.com |publisher=Monster |access-date=23 May 2014 |archive-url=https://web.archive.org/web/20140524061831/http://www.dodbuzz.com/2014/05/22/navy-considers-its-beyond-the-horizon-future/ |archive-date=May 24, 2014 |url-status=dead}}</ref>

The [[AN/APY-9|APY-9]] radar has been suspected of being capable of detecting fighter-sized stealth aircraft, which are typically optimized against high frequencies like [[Ka band|Ka]], [[Ku band|Ku]], [[X band|X]], [[C band (IEEE)|C]] and parts of the [[S-band]]s. 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 jet fighter|fifth-generation fighters]] like 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 Navy'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.<ref>[http://news.usni.org/2014/06/09/u-s-navys-secret-counter-stealth-weapon-hiding-plain-sight The U.S. Navy's Secret Counter-Stealth Weapon Could Be Hiding in Plain Sight] {{Webarchive|url=https://web.archive.org/web/20140709141815/http://news.usni.org/2014/06/09/u-s-navys-secret-counter-stealth-weapon-hiding-plain-sight |date=July 9, 2014}} – News.USNI.org, 9 June 2014</ref>

[[File:Northrop Grumman E-2D Hawkeye with inflight refueling probe in flight on 9 September 2019 (190909-N-PW480-0023).JPG|thumb|The first E-2D with aerial refueling capability was delivered in September 2019.]]
Deliveries of initial production E-2Ds began in 2010.<ref name=Continued_Success>[http://www.irconnect.com/noc/press/pages/news_releases.html?d=179988 "Northrop Grumman's E-2D Advanced Hawkeye Program Demonstrating Continued Success"] {{Webarchive|url=https://web.archive.org/web/20111124043050/http://www.irconnect.com/noc/press/pages/news_releases.html?d=179988 |date=November 24, 2011}}. Northrop Grumman, 9 December 2009.</ref> On 4 February 2010, Delta One conducted the first E-2D carrier landing aboard USS ''Harry S. Truman'' as a part of carrier suitability testing.<ref>{{cite web|url=http://www.asdnews.com/news/33350/NGC_s_E-2D_Advanced_Hawkeye_Completes_1st_Carrier_Landing.htm|title=NGC's E-2D Advanced Hawkeye Completes 1st Carrier Landing|work=asdnews.com|access-date=August 1, 2016|archive-url=https://web.archive.org/web/20110209023945/http://www.asdnews.com/news/33350/NGC_s_E-2D_Advanced_Hawkeye_Completes_1st_Carrier_Landing.htm|archive-date=February 9, 2011|url-status=dead}}</ref> On 27 September 2011, an E-2D was successfully launched by the prototype [[Electromagnetic Aircraft Launch System]] (EMALS) at [[Naval Air Engineering Station Lakehurst]].<ref>{{cite web |title= Navy's new electromagnetic catapult 'real smooth' |url= http://www.app.com/article/20110927/NJNEWS/309270121/Navy-s-new-electromagnetic-catapult-real-smooth- |publisher= Newbury Park Press |date= 28 September 2011 |access-date=2011-10-04}}</ref><ref>{{cite web |title= New carrier launch system tested |url= http://www.upi.com/Business_News/Security-Industry/2011/10/03/New-carrier-launch-system-tested/UPI-13601317652464/ |work= Security Industry |publisher= [[UPI]] |date= 3 October 2011 |access-date= 2011-10-04 |archive-url= https://web.archive.org/web/20111004172633/http://www.upi.com/Business_News/Security-Industry/2011/10/03/New-carrier-launch-system-tested/UPI-13601317652464/ |archive-date= October 4, 2011 |url-status= live}}</ref>  On 12 February 2013, the Office of the Secretary of Defense approved the E-2D to enter full-rate production. The Navy plans for an initial operational capability by 2015.<ref>[http://www.flightglobal.com/news/articles/pentagon-approves-e-2d-hawkeye-full-rate-production-382236/ Pentagon approves E-2D Hawkeye full rate production] {{Webarchive|url=https://web.archive.org/web/20130215094831/http://www.flightglobal.com/news/articles/pentagon-approves-e-2d-hawkeye-full-rate-production-382236/ |date=February 15, 2013}} – Flightglobal.com, February 12, 2013</ref> In June 2013, the 10th E-2D was delivered to the Navy, with an additional 10 aircraft in various stages of manufacturing and predelivery flight testing. On 18 July 2013, Northrop Grumman was awarded a $113.7 million contract for five full-rate production Lot 2 E-2D Advanced Hawkeye aircraft.<ref>[http://www.deagel.com/news/US-Navy-Orders-Five-Lot-2-Full-Rate-Production-E-2D-Advanced-Hawkeyes_n000011750.aspx US Navy Orders Five Lot 2 Full Rate Production E-2D Advanced Hawkeyes] {{Webarchive|url=https://web.archive.org/web/20140714220026/http://www.deagel.com/news/US-Navy-Orders-Five-Lot-2-Full-Rate-Production-E-2D-Advanced-Hawkeyes_n000011750.aspx |date=July 14, 2014}} – Deagel.com, 18 July 2013</ref> On 13 August 2013, Northrop Grumman was awarded a $617 million contract for five E-2Ds until full-rate production Lot 1.<ref>[http://www.navyrecognition.com/index.php?option=com_content&task=view&id=1185 Northrop Grumman Awarded $617 Million for Full-Rate Production E-2D Advanced Hawkeyes] {{Webarchive|url=https://web.archive.org/web/20130902204502/http://www.navyrecognition.com/index.php?option=com_content&task=view&id=1185 |date=September 2, 2013}} – Airrecognition.com, 13 August 2013</ref> On 30 June 2014, Northrop Grumman was awarded a $3.6 billion contract to supply 25 more E-2D, for a total contracted number of 50 aircraft; 13 E-2D models had been delivered by that time.<ref>[http://www.shephardmedia.com/news/digital-battlespace/us-navy-orders-additional-e-2d-aewc-aircraft/ US Navy orders additional E-2D AEW&C aircraft] {{Webarchive|url=https://web.archive.org/web/20140714141635/http://www.shephardmedia.com/news/digital-battlespace/us-navy-orders-additional-e-2d-aewc-aircraft/ |date=July 14, 2014}} – Shephardmedia.com, 1 July 2014</ref>

In December 2016, an E-2D flew for the first time fitted with an aerial refueling capability. This feature will allow the aircraft to double its time on station to five hours and increase total mission time from four to seven hours. The refueling modification will start being built into the 46th plane (out of 75 planned) for delivery in late 2020 costing an additional $2 million per aircraft and the Navy plans to retrofit the feature on all previous Hawkeyes for $6 million per plane.<ref>[https://www.defensenews.com/digital-show-dailies/navy-league/2018/04/11/northrop-to-begin-cutting-in-aerial-refueling-capability-in-e-2d-advanced-hawkeye-production-this-year/ Northrop to begin cutting in aerial refueling capability in E-2D Advanced Hawkeye production this year]. ''Defense News''. 11 April 2018.</ref>{{update inline|date=May 2021}}