Grumman E-2 Hawkeye & C-2 Greyhound (2024)

* In the early 1960s, the US Navy introduced a carrier-based airborne earlywarning (AEW) aircraft, the "E-2 Hawkeye", fitted with radar to help protectnaval formations and support naval activities. The Hawkeye, after manyimprovements, remains an important military asset in the 21st century. Thisdocument provides a history and description of the Hawkeye. A list ofillustration credits is included at the end.

[1] ORIGINS: E-2A / E-2B

* Grumman Corporation, now part of Northrop Grumman, was a pioneer inairborne early warning (AEW) technology, adapting the Grumman Avengertorpedo-bomber to the AEW role under Project CADILLAC at the end of World WarII. In 1955, the Navy Bureau of Aeronautics (BuAer) issued a request for anadvanced carrier-based AEW aircraft. However, BuAer officials realized thatthe spec was so advanced that the new aircraft wouldn't be ready until intothe 1960s, and so the BuAer also ordered two prototypes of a much simpler AEWderivative of the proven Grumman S2F ("Stoof") Tracker antisubmarine warfare(ASW) aircraft as an "interim solution".

The result was the Grumman "WF-2 Tracer", relabeled "E-1B" when the USmilitary converted to a common aircraft designation scheme in 1962. The"Stoof With A Roof" -- or "Willie Fudd", as it was known due to its "WF"designation -- was a capable machine, with a state-of-the-art AN/APS-82 radarand analogue tactical datalinks, and it would remain in service well into the1970s despite its "interim nature".

However, "state of the art" in the 1950s was not all that sophisticated, andthe Navy was still determined to press on to the advanced solution. Afterconsideration of proposals, Grumman's "Model 123" was selected as the winnerof the requirement in March 1957 as the "W2F-1" -- to later become the "E-2AHawkeye". It was the first aircraft ever built from the ground up as an AEWplatform.

Initial flight of the first of three prototypes was on 21 October 1960,though at the outset the aircraft was basically a raw airframe, with littlein the way of vital operational avionics systems. The first flight of aprototype with what could be regarded as a full configuration was on 19 April1961.

* As it emerged, the Hawkeye had a clear evolutionary relationship to theinterim Willie Fudd, and in fact early on it was sometimes called the "SuperFudd". Both machines had high-mounted wings that folded back along thefuselage in classic Grumman fashion; twin engines; a radome on the back;tricycle landing gear and a yoke arresting hook; and a four-fin tail, withthe multiple tailfins providing adequate tailfin area while permittingclearance in the hangar deck of smaller fleet carriers.

However, the Hawkeye was clearly a different aircraft from the Willie Fudd.In particular, instead of the Cyclone radial piston engines of the WF-1, theHawkeye used twin Allison T56-A-8/8A turboprops providing 3,020 kW (4,050SHP) each -- the T56 also being used on the Lockheed P-3 Orion ASW aircraftand the Lockheed C-130 Hercules cargolifter -- driving four-bladedAeroproducts paddle propellers. The main engine intake was below the prop,with an oil cooler intake below the main intake. The Hawkeye featured anadvanced (for the era) General Electric (GE) AN/APS-96 radar system, with theantenna installed in a distinctive new saucer-shaped rotating radome with adiameter of 7.31 meters (24 feet). The Willie Fudd had carried a rotatingantenna array inside a fixed radome.

In more detail, the Hawkeye featured wings that hydraulically folded back inclassic Grumman style along the fuselage, from a wing break just outboard ofthe turboprops. The wings featured ailerons and flaps, with the aileronsdrooping automatically when the flaps were lowered, while the tailplane hadan 11-degree dihedral. All control surfaces were hydraulically boosted, andall flight surfaces featured pneumatic de-icing boots on the leading edgethat "pulsed" to break ice off the leading edges of the wings.

Given the configuration of the aircraft, with some suggestion of a boomerang,it wasn't surprising that it was subject to yaw instability, one pilotcomparing it to "like riding a bicycle with loose handlebars", requiring acertain adroitness when any change was made in its flight. The engines werealso not "handed", the props both spinning in the same direction to simplifymaintenance, and so any throttle changes required some application of rudder.

The aircraft had tricycle landing gear. The steerable nose gear had twowheels and an attachment for catapult launch. Each main gear had a singlewheel, with the gear retracting forward into the engine nacelle, the wheelturning 90 degrees to lie flat. There was a retractable tailskid just behindthe yoke arresting hook to protect the aircraft's tail on take-off, and acooling system pack on the top of the fuselage to help keep the electronicsgear working.

The flight crew included a pilot and copilot, plus three electronics systemsofficers (ESO) or "ravens", all in pressurized accommodations. The crew gotinto and out of the aircraft through a hinge-down door with integral steps onthe middle left side of the fuselage. The ESO section was called the "CombatInformation Center (CIC)" and had a toilet in the rear. There was an accesscorridor between the co*ckpit and the CIC.

The CIC had three consoles, facing left. The CIC was run by a "CICOfficer (CICO)", who was essentially the mission commander -- the pilot andcopilot being responsible only for flying the aircraft. The other twooperators were the "Radar Operator (RO)", who in principle was to supervisethe radar system, and the "Air Control Officer (ACO)", who in principle wasto supervise air communications. Each sat at a workstation with a classicround radarscope. In practice, the three all operated in the radarobservation and air control role, if under a rank hierarchy, with thespecializations of the different roles becoming less prominent as Hawkeyesystem automation improved.

The radar "rotodome" could be lowered 61 centimeters (2 feet) after landingto permit clearance on the hangar deck. In flight, the rotodome was set at apositive angle of incidence to provide enough lift to handle its own weight.It rotated at a rate of 6 revolutions per minute (RPM). The AN/APS-96 radaroperated in the UHF band, around a wavelength of roughly a meter, and couldobserve sea and sky over a radius of 370 kilometers (200 NMI) from theaircraft's operational altitude of 9,150 meters (30,000 feet).

Despite the fact that UHF means "ultra-high frequency", the band isrelatively low frequency by radar standards. UHF was chosen because itwas more indifferent to sea clutter, was less affected by weather, and made small targets look big; all future Hawkeye variants would retain use ofUHF. The AN/APS-96 was innovative in that it provided automatic targettracking: in earlier AEW aircraft, the radar operator had to observe targetblips and figure out the target track and speed on his own. The AN/APS-96was one of the major components of the E-2A's "Airborne Tactical Data System(ATDS)", which linked the radar with a primitive computer system based on amagnetic-drum mass storage, datalinks, and an identification friend or foe(IFF) system. The IFF antenna was mounted on the back of the radar antenna,meaning that the radar scan alternated with IFF interrogation during eachsweep. The E-2A also had a set of radios.

* Deliveries of the E-2A to the Navy began in 1964, with a total of 59production machines handed over. Although sources generally tend to give theimpression that the Hawkeye was as an overnight success, in fact the E-2Adidn't meet spec; it was regarded as so unsatisfactory that production washalted in early 1965. The problem was partly excessive ambition, the 1950sbeing an era of attempts to build futuristic technologies that seemed farmore achievable than they actually were. The E-2A's avionics systems werehighly capable when they worked, but they were unreliable to the point ofuselessness, the rotary-drum mission computer system being a particular weakpoint. The airframe was also prone to corrosion -- a ghastly fault in acarrier-based aircraft. The entire Hawkeye fleet was grounded at one time.

Grumman and the Navy scrambled to implement fixes, the result being the"E-2B", which featured a modernized avionics system built around a LittonL-304 digital computer and some other fixes. The first E-2B performed itsinitial flight on 20 February 1969. 49 of the E-2As were updated to the E-2Bspec to 1971 -- with four others converted to "TE-2A" pilot trainers, and anumber of others being used for test and trials. However, the E-2B wasstrictly an interim fix. The Navy had initiated a "pre-planned productimprovement (P3I)" program in 1968 to give the Hawkeye a thorough workover,which would emerge as the definitive "E-2C".

[2] E-2C BASIC CHARLIE / GROUP 0 HAWKEYE

* Groundwork for the E-2C was laid by trials of the improved GE AN/APS-111radar on an E-2A from 1965 to 1967, which led to the production AN/APS-120radar. The AN/APS-120 featured an "airborne moving target indicator (AMTI)"capability that gave it a limited ability to spot moving targets on land.Two E-2A test machines were modified as prototypes of the E-2C, with thefirst flying on 20 January 1971. Trials proving satisfactory, the E-2C wasordered into production, with the first production machine performing itsinitial flight on 23 September 1972. The E-2C entered fleet service inNovember 1973.

Along with the improved AN/APS-120 radar, the E-2C also featured:

• An "electronic support measures (ESM)" system to spot and locate radar and radio emitters, the system being designated the "AN/ALR-59 Passive Detection System (PDS)". Fit of the PDS meant that the E-2C had a longer and reprofiled nose compared to the snub nose of the E-2A/B; the new nose stretched the length of the aircraft from 17.17 meters (56 feet 4 inches) to 17.5 meters (57 feet 7 inches).

  PDS antennas were also fitted on the endplate tailfins to give 360 degree coverage. The PDS covered four frequency bands and could track up to 250 emitters, characterizing them using a "threat library" that listed the parameters of possible emitters -- frequencies, pulse patterns, and so on.

• The Litton OL-77 computer system, consisting of twin Litton L-304 computers.
• An AN/ASN-92 Carrier Aircraft Inertial Navigation System (CAINS), and an AN/ASN-50 heading and altitude reference system.
• Five UHF and two VHF radios; Link-4 air-to-air and Link-11 air-to-ground datalinks; and an improved AN/APX-72 or -76 IFF system.
• Engines uprated to the T56-A-422 variant with 3,660 kW (4,910 SHP) each, or later to the T56-A-425 variant with the same power rating, but composite instead of metal propellers.

Along with the longer nose, the E-2C also featured a much larger cooling packon top of the fuselage behind the co*ckpit to deal with the more formidableoperational avionics system.

 ___________________________________________________________________ GRUMMAN E-2C HAWKEYE: ___________________________________________________________________ wingspan: 24.6 meters (80 feet 7 inches) width, wings folded: 8.94 meters (29 feet 4 inches) wing area: 65.03 sq_meters (700 sq_feet) length: 17.5 meters (57 feet 7 inches) height: 5.58 meters (18 feet 4 inches) empty weight: 17,300 kilograms (38,100 pounds) max loaded weight: 23,600 kilograms (52,000 pounds) maximum speed: 600 KPH (375 MPH / 325 KT) service ceiling: 9,390 meters (40,000 feet) ferry range: 2,580 kilometers (1,600 MI / 1,390 NMI) patrol endurance: > 4 hours ___________________________________________________________________

After overcoming some initial skepticism, the E-2C proved to be the machinethe Hawkeye was supposed to have been all along. Hawkeyes were fitted from1976 with the improved AN/APS-125 radar that provided Doppler processing andthe ability to track land targets in an automated fashion.

* These "Basic Charlie" machines were then more comprehensively upgradedfrom 1980 to what would later be known as the "Group 0" configuration, whichfeatured:

• The AN/APS-138 radar system, with the "Total Radiation Aperture Control Antenna (TRAC-A)" system providing "sidelobe suppression" -- which meant that it got rid of most of the leakage of the radar signal from off the main line of the radar's sight. Sidelobe suppression improved range and discrimination, and also made the radar harder to jam -- adversary jammers could feed signals back into the sidelobes to give false target direction indications.
• An improved ESM system, the AN/ALR-73 PDS, which could locate targets to about 2 degrees instead of the 5 degrees of the older AN/ALR-59. Its capabilities were otherwise similar to those of the AN/ALR-59.
• More computer memory -- an increment of 16 kilobytes to give a total of 48 kilobytes, pathetic compared to what might be found in a cheap smartphone today -- and a jam-resistant AN/ARC-182 Have Quick radio system.

* A total of 55 Basic Charlies / Group 0 Hawkeyes was delivered to the USN upto 1988. After the trials of the E-2A/B, the E-2C proved an outstandingaircraft in service. It was actually powerful and surprisingly agile, evenestablishing some performance records in its class, though its short fuselage-- designed to the hangar-deck constraints of smaller carriers -- meant thatit could be a handful on single-engine handling. The spinning radome alsowas a bit of a surprise to novice pilots, since it set up torque that wouldskew the aircraft off course unless compensated for by engine trimming.Landing was somewhat tricky since the span was wide and the aircraft had tobe put down precisely on the carrier-deck centerline. Its deck handling wasregarded as very good. Mission endurance was over four hours and theaircraft could be turned around in about 15 minutes, taking off again with afresh crew.

The E-2C was usually called the "Hummer" because of the smooth, resonantsound of its twin T56 engines. The Hawkeye provided an effective partner toGrumman F-14 Tomcat fighters, monitoring the airspace around a carrier groupor battle area and then vectoring Tomcats over the Link-4 datalink to destroyintruders with long-range Phoenix air-to-air missiles. The Hawkeye's baptismof fire with the US Navy was in the Operation EL DORADO CANYON strikesagainst Libya in 1986, and it went to serve in all the major conflicts thatthe Navy has been involved in since. The E-2C also proved useful in airrefueling support, in search and rescue operations, and on a few occasionsas a flying air traffic control center for relief operations.

[3] GROUP 1 HAWKEYE / GROUP 2 HAWKEYE / HAWKEYE 2000

* The Group 0 Hawkeye wasn't the end of the E-2C line by any means, sinceproduction continued with the "Group 1", which featured:

• A further improved AN/APS-139 radar system, coupled to a more powerful Litton processor system that increased the number of targets capable of being tracked from 600 to 2,400. It could also track slow-moving or stationary targets on land, and had greater resistance to jamming.
• A more powerful avionics cooling system.
• New T56-A-427 engines with 3,800 kW (5,100 SHP), improved reliability, and 13% better specific fuel consumption to improve fuel economy. The -427 also featured a "ground idle setting" for foreign operators who didn't operate their Hawkeyes off of carriers.

18 Group 1 machines were built. There was thought of upgrading the old Group0 machines to the same spec, but once a service-life extension program wasfactored in the upgrade was about as expensive as a new-build aircraft, andit didn't happen. Group 0 Hawkeyes were gradually phased out of first-lineservice, though apparently some ended up in Navy Reserve hands, being used totrack drug smugglers trying to fly in over America's southern borders.

* The Group 1 Hawkeyes were actually an interim step to the much moreambitious "Group 2" Hawkeye, which was introduced into service in 1992. Thestep ahead was so dramatic that aircrews described it as "nothing less thanfantastic." The Group 2 Hawkeye featured:

• An AN/APS-145 Advanced Radar Processing System (ARPS), with a much more powerful Litton computer system that increased the number of targets that could be tracked by an order of magnitude. The radar was much more sensitive, with a range about 40% greater than that of the AN/APS-139, and still more resistant to clutter and jamming. It used an ingenious scheme by which target altitude was determined by comparing the "time delay of arrival" of the direct return versus the that of the return bounced off the sea, instead of vertical steering of the antenna. The radome could rotate at variable speed, from 5 to 6 RPM, instead of a constant 6 RPM.
• An improved IFF system, with the IFF antenna boresighted along with the main radar antenna.
• L3 Corporation "Enhanced Main Display Unit (EMDU)" workstations replacing the old radarscopes with 28-centimeter (11-inch) full color displays that provided "symbology" -- identifying different types of targets on the display and providing other information. An ESO could interact with the display using a light pen. There was a small monochrome display underneath the main display to provide alphanumeric data.
• Introduction of a three-channel "Link-16 Joint Tactical Information Distribution System (JTIDS)" in addition to the earlier Link-4 and Link-11 datalinks. The Group 2 brought the complement of radios on board the Hawkeye up to two HF, three VHF-UHF, and two UHF systems to support voice and datalink communications.
• A "Tactical Airborne Mission Planning System (TAMPS)" that was used by planners to create a mission plan that could be loaded in the Hawkeye's computer, as well as a mission recorder.

A total of 12 Group 1 Hawkeyes was brought up to Group 2 standards. Sinceproduction of the Hawkeye is ongoing, it is difficult to know how many moreHawkeyes have been built, but in 1999 the US Navy Hawkeye fleet numbered 89aircraft. At least five of the aircraft were stripped of operationalavionics and used for pilot training under the designation of "TE-2C".

* A "Group 2 Plus" configuration was introduced in the mid-1990s, featuring:

• A "CAINS 2" navigation system with a Global Positioning System (GPS) receiver and laser gyros.
• A Raytheon "Mission Computer Upgrade (MCU)", based on commercial computer technology, much more powerful and compact than the old Litton computer it replaced.
• Improved workstations, the Lockheed Martin "Advanced Computer Indicator Sets (ACIS)", with 48-centimeter (19-inch) displays.
• A new automatic flight control system (AFCS).

The Group 2 Plus upgrades led to the next level of upgrade, known as the"Hawkeye 2000", which included:

• A "Cooperative Engagement Capability (CEC)", which linked together inputs from a range of sources and distribute them to a large number of users on air, sea, and ground platforms, with all the users seeing the same "picture" of the battlespace without great concern over which source provided which part of the picture. It required fit of a new antenna mounted on the fuselage.
• A high-bandwidth satellite communications (satcom) link, and a new AN/ALQ-217 ESM set to replace the older AN/ALR-73.
• A modernized cooling system using environmentally-friendly non-Freon coolant.
• Distinctive new NP2000 composite propellers with eight curved scimitar blades.

The AN/APS-145 radar was retained. The various Group 2 Plus / Hawkeye2000 upgrades were installed in a phased fashion, meaning the configurationof the Hawkeyes being upgraded was a continuously moving target. The firstHawkeye 2000 machine was redelivered in 2001, with 24 machines updated intotal.

[4] HAWKEYE IN FOREIGN SERVICE

* There have been a number of foreign users of the E-2C. Israel was thefirst, buying four "Basic Charlie" machines in 1977:1978. The Israeliscalled the type the "Daya (Kite)", and were apparently the first to use theE-2C in combat, with E-2Cs supervising the entirely one-sided 1982 IsraeliAir Force "Turkey Shoot" against Syrian fighters in the skies over the BekaaValley in Lebanon.

The Israeli E-2Cs were mothballed in 1994, the Israelis having moved on totheir own AEW platforms, based on the Phalcon radar system. One of the threeDayas ended up as a museum display, while the other three were refurbished byIsrael Aircraft Industries and sold to the Mexican Navy, with deliveries in2004. The other buyers included:

• The Japanese Air Self-Defense Force obtained eight Group 0 E-2Cs, with deliveries from 1982 to 1985, followed by a batch of five Group II machines in 1992:1993.
• Egypt obtained five Hawkeyes in 1986 and a sixth in 1993, with these machines built to a unique "Group 0/II" or "Group One & One-Half" configuration -- featuring the Group 0 AN/APS-138 radar but the Group II EMDU displays and some other Group II gear. In late 1999, Egypt ordered an "Export Hawkeye 2000" upgrade for five of its Group 0/II Hawkeyes, and also purchased another ex-USN E-2C that was brought up to the same configuration. The sixth Group 0/II machine was updated in 2008. A new-build Hawkeye 2000 was ordered in 2015, bring the total up to eight.
• Singapore obtained four Group 0 machines, which went into operation in 1987.
• Taiwan obtained four Group II machines in 1995, with these machines being given the designation of "E-2T". Some sources claim they were updated E-2Bs, but that is an error; the upgrade cost would have been about that of a new-build airframe. They were later updated to Hawkeye 2000 standard, being redesignated "E-2K".
• The French Aeronavale -- naval air arm -- bought four Group II Plus machines from 1997. The Aeronavale was the only foreign Hawkeye user to fly the aircraft off carriers, the E-2Cs going into service on the new fleet carrier CHARLES DE GAULLE. They later received upgrades in service.

[5] E-2D ADVANCED HAWKEYE

* Even as the Hawkeye 2000 was being delivered to the fleet, the Navy waslooking towards the next generation. The result is the "E-2D AdvancedHawkeye". It looked much like previous variants, but was generally updatedunder the skin. Many aircraft assemblies were replaced by more modernassemblies made of improved materials, with an emphasis on large one-piecemachined parts that reduce weight and easy assembly. Maximum carrier landingweight was increased. Most significantly, the E-2D carried asubstantially improved AN/APY-9 radar, integrated into a completelymodernized operational avionics system.

The AN/APY-9 was a "hybrid" radar, with the antenna rotating to scan the sky,but featuring a high-resolution passive phased array / electronically steeredsubsystem to focus on specific targets. The AN/APY-9 had improved processingand greater sensitivity, allowing it to observe a volume of airspace threetimes greater than that of the E-2C's AN/APS-145 radar. One of itssignificant new features was "space-time adaptive processing (STAP)" softwarethat allowed the radar to alter its operation as required by circ*mstances,giving it the ability to pick up targets in rough terrain and urban sprawl --reflecting the more varied operational environments faced by the US Navy inthe 21st century. The radome also included an IFF antenna, and wascomplemented by an advanced digital ESM and an infrared imager, with theoperational avionics system performing "sensor fusion" to produce a singleannotated "map" of the airspace environment.

The operational avionics system featured a new glass co*ckpit, and threeworkstations with three 43-centimeter (17-inch) color flat-panel displays.Although the E-2D leveraged heavily off of Hawkeye 2000 software, about twomillion lines of code were added, providing much greater integration ofthe pilot, copilot, and three systems operators -- for example, the pilotor copilot could see a workstation display on a co*ckpit display with theflick of a switch. The improved integration allowed the pilot or copilot tolend a hand as a systems operator.

The E-2D also featured "Tactical Targeting Networking Technology" datalinksystem to share data with or provide direction to other Navy sea and airassets. One pilot said there was no comparison between the Hawkeye "Charlie"and the "Delta":

BEGIN_QUOTE:

The E-2D is an awesome aircraft. It may look like an E-2C from the outside,but once you are inside, it is non-recognizable to anyone who has flight timein the Charlie ... it is leaps and bounds ahead of the [Charlie's] technology...

END_QUOTE

The E-2D was fitted with uprated Rolls-Royce T56-A-427 engines, driving the8-blade composite propellers, to deal with higher take-off weight. Systemupgrades are already in planning, such as an improved CEC capability and acapability to intrude into adversary radio communications networks. Regularsoftware updates are scheduled, for example to add improved targetidentification, more systems automation, and improved datalink access -- withone goal being to ultimately permit remote operators at ground or shipboardstations to act as additional E-2D crew members. The E-2D was also designedwith an "open architecture" to permit relatively easy upgrades of hardware.

Full-scale development of the E-2D began in 2003, with initial flight of thefirst of two prototypes in August 2007. Initial delivery of the E-2D to theNavy was in 2010 for operational evaluation, with introduction to service in2014. The Navy plans to acquire 75 E-2Ds, replacing the E-2C by 2025. Japanis in the process of obtaining 18 E-2Ds, as a follow-on to Japan's E-2Cs, withinitial delivery in late 2019; the French are similarly planning to buy threeE-2Ds, with delivery in 2027 and 2028. Taiwan is talking about updatingtheir E-2Ks to E-2D spec, while the E-2D has been offered toIndia.

The E-2D fleet is being upgraded with a mid-air refueling capability; an E-2Cand E-2D were fitted with a probe as a test. New-build E-2Ds are now beingproduced with the probe, with the first being redelivered in late 2019, bandolder machines will be upgraded with it. There is also interest in adding afuel tank inside the wing outboard of the wing fold to increase endurance.Software updates are ongoing.

Other upgrades in the works include:

• A new mission computer and an updated co*ckpit, with new displays and head-up displays (HUD). Computer / display hardware tends to go obsolete at a rapid rate, making upkeep difficult.
• An Automatic Information System (AIS) receiver, being a tracking system for maritime traffic.
• An Improved Landing Mode (ILM) system to make carrier landings easier, particularly under adverse conditions.
• Improved networking, with a dual-satcom transceiver system.
• Improved, smarter battle-management tools, plus improved data security.
• An "open architecture" to make the Advanced Hawkeye easier to upgrade.

Improved seats and other crew comforts are being considered. The Japanesestipulated a microwave oven and toilet for their E-2Ds; it is possible theywill be added to US Navy E-2Ds as well. The Hawkeye is likely to keep flyinginto the 2040s.

[6] C-2A GREYHOUND

* The Hawkeye's sister design, the "C-2A Greyhound Carrier Onboard Delivery(COD)" aircraft, was designed as a cargo and personnel transport capable ofcarrier take-offs and landings. The C-2A was based on the Hawkeye butfeatured a largely redesigned fuselage for cargo carriage, with greater fuelcapacity and strengthened nose gear to handle higher weights. The tailassembly was also redesigned, since it did not have to compensate for theaerodynamic interference of the Hawkeye's radome, and lacks the dihedral ofthe Hawkeye's tail assembly.

The Greyhound was developed roughly in parallel with the Hawkeye, with two flight prototypes and a single static-test airframe built. The firstprototype performed its initial flight on 18 November 1964. Initialdeliveries to the fleet were in 1966.

Like the Hawkeye, the Greyhound was initially powered by twin Allison T56-A-8turboprop engines, with improved engine variants refitted in time, andfeatured the traditional Grumman side-folding wing scheme. An auxiliarypower unit allowed engine starting and ground operation at remote locationswhere ground support facilities were lacking. The C-2A had a crew of four,and was fitted with an extensive avionics suite, including radios, navigationgear, and carrier landing systems. The Greyhound could carry 4,535 kilograms(10,000 pounds) of cargo, or 39 passengers, or 20 litters with fourattendants. If operating off land bases instead of a carrier deck, it couldcarry up to 6,800 kilograms (15,000 pounds) of cargo. It was also capable ofperforming "search and rescue (SAR)" duties as a secondary mission.

Cargo was loaded though an aft cargo door with an integral ramp, moved intoplace with an overhead powered winch system in the cargo bay, and lashed downusing a cage system. The rear cargo door could be opened in flight for airdropof supplies. Ferry tanks could be fitted in the cargo hold, and apparentlythere was provision for an external tank or buddy refueling pod on each sideof the fuselage.

 ___________________________________________________________________ GRUMMAN C-2A GREYHOUND: ___________________________________________________________________ wingspan: 24.56 meters (80 feet 7 inches) width, wings folded: 8.94 meters (29 feet 4 inches) length: 17.32 meters (57 feet 10 inches) height: 4.84 meters (15 feet 11 inches) empty weight: 16,485 kilograms (36,346 pounds) loaded weight: 26,080 kilograms (57,500 pounds) max speed at altitude: 575 KPH (360 MPH / 310 KT) cruise speed: 480 KPH (300 MPH / 260 KT) service ceiling: 10,200 meters (33,500 feet) range: 1,930 kilometers (1,200 MI / 1,040 NMI) ___________________________________________________________________

Only 19 Greyhounds went into service from 1965 to 1968, plans foracquisition of a dozen more having been canceled. All these initial-buildaircraft were put through a "service life extension program (SLEP)" beginningin 1973 to keep them in operation.

In 1984, the Navy awarded a contract to Grumman for 39 new "C-2A(R)"aircraft, where the "R" stood for "Reprocured", with the first going intoservice in 1985. These aircraft featured airframe reinforcement and avionicsimprovements over the original C-2As, which were all phased out by 1987. TheNavy has performed some additional updates on the C-2A(R) -- a new SLEP,avionics upgrades (including the CAINS II system), and the NP2000 eight-bladepropellers.

However, the Greyhound's days are numbered, with the Navy now replacing itwith a COD version of the Marines' Bell-Boeing MV-22B Osprey tiltrotor, the"CMV-22B", with additional fuel tanks for extended range. The USMC hadpushed to obtain the CMV-22B to extend the "footprint" of the Marine Ospreyfleet. Initial deliveries of the CMV-22B began in 2020, with the Greyhoundto be out of service by 2026.

[7] COMMENTS, SOURCES, & REVISION HISTORY

* In the late 1980s, the US Coast Guard (USCG) briefly operated four E-2Cs onloan from the Navy to hunt for drug smugglers. USCG brass were impressedwith the Hawkeye and wanted to acquire their own fleet of AEW aircraft.Since longer endurance was needed, the concept solidified as a modificationof a Lockheed HC-130H Hercules transport, which was operated by the CoastGuard, fitted with AN/APS-145 radar and a subset of the associated Hawkeyeoperational avionics.

General Dynamics performed the conversion, with the aircraft performing itsinitial flight as the "EC-130V" on 31 July 1991. The system, nicknamed the"Herkeye", apparently worked as per specification, but it proved tooexpensive and there was no follow-through on the program. The EC-130V waspassed on to the US Air Force in 1993 for test and trials use.

* The US Customs Service -- now the Customs & Border Protection Service --also became interested in an AEW system based on Hawkeye avionics, resultingin mating the E-2C radar system to surplus Lockheed P-3 Orion maritime patrolaircraft airframes. The first of these "P3 AEW" machines performed itsmaiden flight on 8 April 1988. It was fitted with AN/APG-125 radarinitially, but later updated to AN/APG-138 radar. Three more were deliveredto 1993, with another batch of four delivered beginning in the late 1990s.

All the later machines were delivered with AN/APG-138 radar; the entire fleetof eight was then updated with AN/APG-145 radar. Customs also obtained eightP-3 Orions as "Long Range Trackers (LRT)", featuring a sensor suite but noAEW system and radome. The P-3 AEW and P-3 LRT often operate in teams.Customs P-3 machines were put through a SLEP from 2008 to keep them inservice.

* Sources include:

• "E-2 Hawkeye" by David Donald, WORLD AIR POWER JOURNAL, Volume 32 / Spring 1998
• "E-2C Hawkeye: The Navy's Eye In The Sky" by Brad Elward, COMBAT AIRCRAFT, January 1999
• "Without New AEW Aircraft, Navy Considers Improved E-2" by Robert Wall, AVIATION WEEK, 21 February 2000
• "E-2C Radar Options Emerge" by Robert Wall, AVIATION WEEK, 26 June 2000
• "Advanced Flying Saucers" by David A. Fulghum, AVIATION WEEK, 30 April 2000
• "E-2D Flies" by David A. Fulghum, AVIATION WEEK, 13 August 2007
• "Advanced Hawkeye", AIR INTERNATIONAL, May 2019

* Illustrations credits:

• BANNER: Grumman E-2C Hawkeye 2000s / 2007 / US Navy
• Grumman E-2C Hawkeye / MIDWAY Museum, San Diego CA / 2007 / author
• Grumman E-2C Hawkeye taking off from USS KITTY HAWK / 2004 / PM3C Jason T. Poplin, US Navy
• Grumman E-2D Hawkeye on USS RONALD REAGAN / 2017 / US Navy
• Grumman C-2A Greyhound / Cheyenne WY USA / 2006 / author
• Grumman C-2A Greyhound landing on USS NIMITZ / 2017 / MCSS Kennishah J. Maddux, US Navy

* Revision history:

 v1.0.0 / 01 jun 07 v1.0.1 / 01 apr 09 / E-2D first flight. v1.0.2 / 01 mar 11 / Review & polish. v1.0.3 / 01 feb 13 / Update on Customs P-3 machines. v1.0.4 / 01 jan 15 / Notes on flight handling. v1.0.5 / 01 dec 16 / CMV-22B. v1.0.6 / 01 nov 18 / Review & polish. v1.0.7 / 01 oct 20 / Illustrations update v1.1.0 / 01 aug 22 / Review & polish. v1.1.1 / 01 sep 22 / Minor update. v1.1.2 / 01 jun 24 / Review, polish, & update. (+)