Editing Grumman E-2 Hawkeye (section)

===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>