About the Sentry AEW1 E3D


Commonly known as AWACS (Airborne Warning And Control System) after its US nomenclature, the E-3D Sentry AEW.Mk 1 (Sentry AEW1 E-3D) is an airborne early warning (AEW) and command and control aircraft.  


The Sentry monitors airspace to provide threat detection of adversary aircraft and situational awareness on friendly assets.  Information gathered by the Northrop Grumman APY-2 radar is processed by the mission crew and disseminated via a variety of data links and communication systems.

Sentry also has the capability to detect ships, relaying information to maritime aircraft or allied vessels for further investigation.  Its electronic support measures equipment enables the E-3D to gather emissions from other radar systems and emitters, enhancing the crew’s understanding of the environment in which it is operating.

E-3D in level flight showing off its refuelling receptacle in the upper forward fuselage.
Can be refuelled by hose-and-drogue tankers.
Image by: SAC Andy Stevens


Seeking a modern, jet-powered replacement for the piston-engined types it was operating in the AEW role, on July 23, 1970, the US Air Force chose the Boeing 707-320 airliner as the base airframe for a new Airborne Warning And Control System aircraft.

Modified with a Westinghouse AN/APY-1 radar system, its antenna covered by a massive rotating radome held over the rear fuselage, the first of two EC-137D prototypes completed its initial flight on February 5, 1972. After an extensive test programme, the E-3A production version entered service in March 1977.  Although the type is officially named ‘Sentry’, the USAF designates it E-3 AWACS.

In January 1972, just days before the EC-137D took off for the first time, 8 Sqn, RAF, re-formed to operate the Avro Shackleton AEW.Mk 2, a conversion of the Shackleton MR.Mk 2 to accommodate radar systems recently removed from Fleet Air Arm Fairey Gannet AEW platforms.  With its dedicated and highly skilled crews, the Shackleton provided a useful stopgap capability and it was expected that the Nimrod AEW.Mk 3 would replace it sometime in the early to mid-1980s.

A dramatic modification of the Nimrod MR.Mk 1, the AEW.Mk 3 first flew on July 16, 1980, but suffered insurmountable technical problems, primarily caused by the incompatibility of its avionics and airframe; it was finally cancelled early in 1987.

With an urgent need to replace the piston-engined Shackleton, the Ministry of Defence looked to a solution that had previously been suggested during the Nimrod AEW.Mk 3 programme and ordered seven E-3s.

Officially designated Sentry AEW.Mk 1 in RAF service, but commonly known as E-3D, the new aircraft differed from the US fleet in its powerplant of more efficient CFM56 engines.  The Shackleton remained on strength until 1991, 8 Sqn taking its first E-3D at RAF Waddington, Lincolnshire in July.  Little more than a year later, the type was in action over the Balkans, before making a valuable contribution to Operation Warden over northern Iraq in 1994.

Today the Sentry is fully integrated into the ISTAR Force, yet retains its core competencies of airborne early warning and airspace management.  Its capability is no more appreciated than in the skies over Iraq and Syria, where an ongoing commitment to Operation Shader sees the E-3D deconflicting airspace, providing ‘big picture’ situational awareness for Coalition aircraft and early warning of aircraft movements outside Coalition control.  The 2015 Strategic Defence and Security Review called for Sentry to remain in service until 2035.

Header image by MoD

Based at


Boeing E-3D Sentry AEW.Mk 1 (Sentry AEW1 E-3D):

  • Powerplant: four 24,000lb st (107kN) CFM International CFM56-2A3 turbofans
  • Length: 152ft 11in (46.61m)
  • Height: 41ft 4in (12.60m)
  • Wingspan: 145ft 9in (44.42m)
  • Wing area: 3,050sqft (83.40m2)
  • Empty weight: 185,000lb (83,990kg)
  • Maximum take-off weight: 334,000lb (151,636kg)
  • Cruising speed: Mach 0.72 Rate of climb 2,000ft/min (610m/min)
  • Range: 5,000nm (8,046km)
  • Endurance: 10 hours
  • Service ceiling: 43,000ft (13,106m)

Sentry AEW1 (E-3D) Recognition

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