Extended horizons: early warning assets expand their repertoire

During the latter stages of the Second World War, as US and British naval forces faced the fierce onslaught of Japanese air attacks in the Pacific, the need to provide extended surveillance and threat warning became apparent. With shipborne radars limited by the radar horizon, the answer, proven through the US Navy's (USN's) pioneering Project 'Cadillac', was to fit a search radar in an airborne early warning (AEW) aircraft, launched from and recovering to an aircraft carrier, which could act as a radar picket positioned 'up threat'.

In 1982 the Falklands (Malvinas) conflict provided a stark reminder of the vulnerability of surface forces operating in a hostile air environment without AEW support. The absence of such a capability in the face of sustained air attack gave the UK Royal Navy (RN) insufficient warning to counter threats at long range, and directly contributed to the loss of several ships.

The last two decades, however, have seen a shift away from classic 'open ocean' AEW and intercept control. Instead, there has been a move towards a broader spectrum of littorally focused missions such as: airborne battle management command and control; strike control; maritime domain awareness; border and coastal surveillance; search and rescue; and disaster/humanitarian relief co-ordination and control. This evolution of carrier-borne airborne surveillance and control is today reflected by developments on both sides of the Atlantic.

Northrop Grumman, through what was the Grumman Corporation, can trace a history in AEW and control going back to the mid-1940s, when a TBF-3 Avenger torpedo bomber was modified to carry a first-generation airborne search radar. It later developed the E-1B Tracer (a derivative of the C-1 Trader carrier onboard delivery aircraft) for the USN in the mid-1950s.

In 1964 the USN introduced Grumman's E-2A Hawkeye, the service's first purpose-designed carrier-borne AEW aircraft. The E-2A was later upgraded to E-2B standard through the introduction of a (then new) programmable high-speed digital computer.

The next major evolution of the Hawkeye, the E-2C, began in 1968 with the first prototype flying in 1971 and deliveries of operational aircraft to the USN began two years later. During the course of its career, the E-2C marquee has itself been the subject of five substantive system upgrades, culminating in the current production Hawkeye 2000 configuration (the last two aircraft built to this standard are due for delivery in 2009).

Entering initial service from 2003, Hawkeye 2000 expanded on the previous E-2C Group II marque by introducing a Mission Computer Upgrade/Advanced Control Indicator Set (MCU/ACIS), integrating the Co-operative Engagement Capability (CEC) using the AN/USG-3 common equipment set, replacing Mini-DAMA communications with an ARC-210 communications set and introducing the Lockheed Martin AN/ALQ-217 electronic support measures (ESM) system in place of the elderly AN/ALR-73. A vapour cycle upgrade was undertaken to meet the increased avionics cooling requirement, while also introducing an environmentally friendly cooling refrigerant (R-134a).

New Hamilton Sundstrand NP2000 eight-blade propellers have also been brought into service aboard Hawkeye 2000. These offer a range of benefits including higher reliability, lower vibration and noise, improved speed governing and response, smoother engine shutdowns/starts, reduced feather drag, and no engine/propeller/airframe loads issues.

Almost 45 years after the E-2A entered service, the latest evolution of the Hawkeye line is today in flight testing ahead of its scheduled 2011 initial operating capability. Its appearance remains recognisably common with an antecedent now several generations removed, but the radar and associated mission system of the new E-2D Advanced Hawkeye (AHE) will offer functionality and performance undreamt of when the original Hawkeye made its debut.

Image caption: E-2C Hawkeye comes into land aboard USS Nimitz. 588 of 4485 words