'The government should rethink plans to scrap Sentinel in 2015'

18 April 2012

Director of The Air League Andrew Brookes discusses the uncertain future of a key part of the UK's ISTAR 'triad' and argues that there is no obvious successor to fill Sentinel's unique role

On 14 April it was reported that RAF Boeing Sentry E-3D aircraft were temporarily out of service as a precautionary measure after a fault was discovered during a routine inspection at RAF Waddington in Lincolnshire. A Ministry of Defence spokeswoman said that there was no loss of operational capability.

We can rest assured that the E-3Ds will be back on line soon, not least because they are slated to play a major part in a "defence of London during the Olympics" exercise planned for early May. On 29 February, Defence Secretary Philip Hammond flew on board a Sentry to witness a pre-Olympics exercise codenamed Taurus Mountain 2, designed to test the ability of the armed forces to respond to an airborne threat. RAF Typhoon aircraft and helicopters were scrambled to intercept and identify a suspicious aircraft, guided by controllers and observers based both in the air and on the ground. That said, the E-3D is geared to operating in the airborne surveillance and command-and-control role over larger tracts of airspace than the Home Counties, as was demonstrated during Ellamy operations in Libya.

The E-3D Sentry forms one arm of the UK Intelligence, Surveillance, Target Acquisition and Reconnaissance (ISTAR) triad which originally consisted of Sentry, Sentinel R1 and Nimrod R1 aircraft. There are five Sentinel R1 aircraft which are based alongside the E-3Ds at Waddington. Sentinel R1s are converted Bombardier Global Express aircraft fitted with a Raytheon Dual Mode Radar similar to the U2 ASARS radar which collects Synthetic Aperture Radar (SAR) imagery and Ground Moving Target Indicator (GMTI) data. Sentinel was originally conceived as the British E-8C JSTARS for conventional war-fighting operations, tracking armoured formations and conducting strategic reconnaissance tasks. However, the Sentinels have added considerable value during counter-insurgency operations in Afghanistan, and in 2011 they provided vital intelligence to enable coalition air assets to protect civilians from pro-Gaddafi forces as well as to provide cross-cueing for other assets. Some 2,000 Sentinel hours were flown during Ellamy and the five aircraft were in great demand in support of the differing Afghan and Libyan theatres.

The 2010 SDSR announced that the SAR and GMTI capability provided by Sentinel would be retained only until the UK's involvement in Op Herrick had ceased. The implication is that the Sentinel system will remain in service until 2015 by which time a suitable (unmanned?) platform will have been developed onto which this valuable ISR capability can be transferred.

The third leg of the ISTAR triad – the Nimrod R – will be replaced by three Airseeker Rivet Joint aircraft, the first of which is scheduled to enter service in 2014. Until then, the UK's airborne signals intelligence capability is being sustained by a co-manning agreement under which UK personnel are deployed operationally on board USAF RC-135W Rivet Joint aircraft.

Standing back out of the limelight but equally integral to the ISTAR role are five King Air 350 Shadow Mk 1 aircraft. Operated by 14 Sqn RAF with army personnel down the back, the Shadow R1s are optimised for Special Forces' duties. Far from being short of ISTAR assets, it is arguable that the Shadow R1s are an example of duplication generated by the SF mafia.

So notwithstanding the temporary grounding of the Sentry fleet, the UK ISTAR triad is firmly focused at the centre of the UK defence effort. The triad is still necessary because the Sentry is optimised for the air campaign while Sentinel is geared to the land battle. Sentinel has proved itself to be a very valuable and flexible asset, and the software is being re-programmed to give it a maritime reconnaissance capability which will prove invaluable with the demise of the MR Nimrod. I don't see any platform replacing Sentinel over the next few years and therefore it would make sense to revisit that SDSR decision before too long.