Options for the future delivery of the UK’s Airborne Warning and Control capability are being explored, including upgrades to the current E-3 Sentry fleet, however some industry commentators are arguing for a new aircraft type altogether.

Madeleine Moon, Chair of the Defence Sub-Committee, asked:

“To ask the Secretary of State for Defence, when he plans to run a competition to replace the RAF’s airborne early warning aircraft.”

Guto Bebb, Parliamentary Under-Secretary of State for Defence, answered:

“No decision has been made with regard to the future delivery of the UK’s Airborne Warning and Control capabilities, although a range of options are being explored. I am withholding details of the level of funding allocated for the future delivery of the RAF’s Airborne Warning and Control System as releasing them would prejudice commercial interests.”

The large sums of money allocated to upgrading the E-3D fleet should be used to purchase a more advanced off-the-shelf aircraft, a defence analyst has argued. Justin Bronk, Research Fellow, Airpower and Technology, outlines options for replacing the E-3 fleet in his paper ‘The Future of Air C2 and AEW: E-3 Sentry, Threat Technologies and Future Replacement Options’:

“The RAF’s E-3Ds need a £2-billion CSP both to bring them to rough parity with current US and French standards by the mid-2020s and to stretch the fleet out to 2035 in the process. However, the E-3, even in modernised form, is no longer a cutting-edge ABM&S system in a world where proliferating long-range missile systems and emerging non-Western low-observable fighters can force it to stay hundreds of kilometres from contested airspace, placing a higher premium on BLOS communications capacity rather than onboard sensors.

Even when it is able to operate closer to the battlespace, the AN/APY-1/2 mechanically scanned radar array common to all E-3s has significant inherent limitations in terms of its ability to detect low-observable, very slow moving and hypersonic threats, unlike more modern AESA-equipped AWACS types already in service with the US Navy and various air forces around the world. An AESA-equipped ABM&S platform with improved communications node capabilities, based on a commercial-derivative airframe, seems a logical alternative option which could provide the RAF with a more capable and efficient alternative to extending the life of the E-3D over the next 20 years.

Such an approach would incur programmatic risk and acquisition and integration costs, but the MoD should examine and weigh these against the expensive work required to extend the E-3D with a view to ensuring the RAF has the best capability possible for the next two decades.”

The US designed E-3D Sentry AEW.Mk 1 is an airborne early warning (AEW) and command and control aircraft in British service, but what does that mean?

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.

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. 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.

Today the Sentry is fully integrated into the ISTAR Force, yet retains its core competencies of airborne early warning and airspace management. The 2015 Strategic Defence and Security Review called for Sentry to remain in service until 2035.


  1. Please lets standardise on an airframe currently in service.

    This may be a really stupid question but can the tankers not be fitted with a 4 faced radar built (CEAFAR) into the body, with the Typhoon Aesa radars built into the nose and tail and a MADL connection.

    I assume this is barking mad, but at least lets use the same airframes please and standardise on engines, parts etc.

      • I think the point being made was we should use airframes in current and future use – like the A330 used for the MRTT Voyager. In ‘A330neo’ form now being delivered it is a very capable airframe in lift and range, has all the main parts like engines, wings, undercart and much more manufactured here in the UK

        The cynic in me however suggests the MoD are already asking Boeing for a 767 / 777 / 787 AWACS ignoring the complete debacle of how they have failed to deliver one operating 767 (KC-46) tanker. And of course they will fit GE not RR engines.

        Sadly the days of evaluating what is also good for the UK economy and manufacturing are long gone in any Ministerial decisions ……

        • I do think that UK aircraft should always have RR engines, wherever possible and in the commercial world airlines can choose the engines on Boeing or Airbus. We really need to support RR.

          • The Rolls Royce AE engines power the C-130, the Osprey, Global Hawk, and Triton, all US systems. Should the US only use US engines in their aircraft? It would only be fair by your reckoning.

        • They’re much more likely talking to Boeing about the E-7 Wedgetail that the RAAF are fielding. After all, we are buying 9 P-8As, so why not go for the very succesful 737 frame? I’m not at all convinced AWACS need the massive airframe of a A330 / 767 sized aircraft, with computing becoming much more compact over the decades. Cooling is always a concern but that can be overcome, it’s just good engineering.

          The other way to look at this is shouldn’t a distributed number of platforms be used so losing an AWACS doesn’t knock out all control in the area?

        • Boeing will fit whatever engines the customer want. The E-3D and E-3F (France) have CFM56 rather than the GE standard fit.

      • I dont think all the tankers are being used – that’s one of the reasons why they are doing transport activiites, but I guess the main point is standard is on the airframe at the very least.

    • Not a stupid question. It’s already been looked at. Putting two EriEyes on the roof of the A330. Saab and Airbus were both keen. But probably won’t happen. More logical to buy B737 based Wedgetail off the shelf a la RAAF. Tankers, given their CONOPS/CONUSE, probably better employed as a collect, distribute/reachback node for F35 so that we can exploit the sensor fusion and reconnaissance capabilities of the platform. To my limited knowledge, that’s also being looked at…

  2. Surely the long term option is a NATO multi nation project, no doubt the US will be the lead partner. This offers the lowest cost and risk as a way forward.

  3. 2 Billion??

    To upgrade what? Radar? Avionics? Engines? Software? C3 capability? For 6 planes.

    Again the costs are breathtaking.

    • For 2 billion they could have 6 brand new E-7 Wedgetails that would have higher availability and lower operational costs. Skip the upgrades and go straight to the new available aircraft.

        • One very obvious drawback of Wedgetail, which people seem to be overlooking, is that it doesn’t have full 360 degree coverage. By which I mean that radar range is far lower in the forward and aft 60 degree cones.

      • Always best to go for what works, now! Believe me, I’ve lived through many programmes. Then develop it for as long as you like to do other things. Sometimes though you need to break the mood and try something new, but believe me, it will take long, be painful and very expensive… in the case of a Sentry replacement? Wedgetail is by far the safest option….

    • Yeah, this is an obvious alternative. Saab has done a lot to improve the kit and now it can operate at higher altitudes as well. Worth a look… also could have commonality with a similar Saab replacement product for Sentinel…

  4. We could move away giant AWACS aircraft that are increasingly vulnerable to long-range SAMs like S-400.

    What about moving towards networked, high-endurance, very high-altitude radar drones? Multiple drones flying in formations hundreds of miles across could cover huge amounts of airspace. Shoot one down and the others would adjust their positions relative to one another to cover the gap. Lose an E3 to an S-400 and you lose 15 people. You also now have a massive hole in your defences.

    Whatever solution the politicians find, I hope that survivability is carefully considered.

    • Really Interesting idea, i’d think they would be worried about jamming as that seems to be a big issue with drones in high end warfare in general but I hope they consider this idea.

    • I have limited knowledge myself but I’ll have a stab at answering those questions. As I understand the main reason current AWACS type radar are so enormous is because of their horizontal range e.g. Sentry has a look up range of 650km. Current radar look for Doppler shifts in radar returns when doing look down searching, because otherwise the Earth (much larger than a fast jet) would completely clutter the image gained as it is a good reflector. This look down searching requires much less energy than horizontal searching because of the decreased ranges (70000ft = 21.3km). So, it is reasonable to think that if all of these drones were doing look down searching exclusively because of their numbers and altitude, that they would not need large, powerful radars. The low density of air at high altitude might make it difficult for a small drone to carry even a small radar, but it’s worth noting that whatever solution is picked is probably over a decade or two away, so there is always room for improvements in radar technology.

    • Lovely idea. The technology (I mean really working, down to earth technology) is still a few years away. Better to start with Wedgetail, networked with F-35 and Voyager and then gradually creep to adding Global Hawk (or similar) a few years later working alongside (and controlled by?) the Wedgetail as gap filler and to get closer to the FEBA…

  5. Global Hawk, for instance has a range of 14000 miles (32 hours endurance) at 60,000 feet. Several radar equipped and networked aircraft like these working cooperatively might provide a very flexible, survivable solution.

    • I don’t know much about radar but a question that occurs to me, that might well have a definitive and reassuring answer, is can a big radar such as something on an E3D type aircraft be adequately replaced by smaller units that are small and light enough to fit within the payload constraints of something like Global Hawk? As sub-questions – How much power is the minimum required to be able to do ground surveillance from 60,000 feet? Is there a minimum antenna size to get a required resolution at a specified range? Does resolution have any relationship to power for that matter?

      As I said, I don’t know much about the practicalities of radar (as you might have discerned from my questions above!) so I’m not arguing against your idea, just wondering whether current technology is up to it and what sort of payload capacity the smaller networked drones might need to have.

      • All great questions. My MSC thesis detailed potential upgrade options to the current E-3D radar. Range related to power, therefore resolution also. If you google the radar range equation you’ll see that range is proportional to the 4th route of the transmitter power (amongst many other things) so very valid points. However, technology has come a long way since this radar was designed. I like the multi assets coverage approach but jamming would be a huge consideration. It avoids the SPOF issue created by a SAM threat. In a former life I was also an E-3D controller, so I am still pondering the mission side of how this approach would be resolved.

      • I have limited knowledge myself but I’ll have a stab at answering those questions. On AESA radar, the antennae are tiny, so no need to worry about that. As I understand the main reason current AWACS type radar are so enormous is because of their horizontal range e.g. Sentry has a look up range of 650km. Current radar look for Doppler shifts in radar returns when doing look down searching, because otherwise the Earth (much larger than a fast jet) would completely clutter the image gained as it is a good reflector. This look down searching requires much less energy than horizontal searching because of the decreased ranges (70000ft = 21.3km). So, it is reasonable to think that if all of these drones were doing look down searching exclusively because of their numbers and altitude, that they would not need large, powerful radars.

        The mechanically scanned phased array radar that fits US F16s has a look down range of 50km, and a weight of 164kg – electronic scanning decreases weight. The low density of air at high altitude might make it difficult for a small drone to carry even a small radar, but it’s worth noting that whatever solution is picked is probably over a decade or two away, so there is always room for improvements in radar technology.

  6. USAF FY2019 budget : JSTARS Recap Finally Killed

    1) JSTARS recap finally killed, US Air Force stating that the big, large aircraft, RC-135 Rivet Joint, E8C JSTARS & E3 EAWACS are operationally vulnerable and indefensible from current threats (China and Russia eg S400 & new S500, same vulnerability would apply to the P-8A & MQ-4C).
    2) Cancelled the Space Based Infrared satellites 7 and 8 which monitor incoming missiles, USAF saying not survivable against the new anti satellite threats, shifting to smaller and agile satellites. Mention of “steerable” and jam-resistant GPS satellites”. Also calls into question the survivability of the large comms and GPS satellites.
    3) USAF spending money on AOA for both “Advanced Battle Management System Analysis of Alternatives (ABMS AOA) to consider the best ways forward in light of the much changed threat environment”


    • Yea, but we’re talking of at least a 30 year horizon here before the US comes out with anything new… at least. Wedgetail can be bought off the shelf now. In time, the technology will be available for drones to take over, gradually…

  7. As a trivial point it’ll be good to get away from the name – I keep confusing Sentry with Sentinel, and when you’ve done that once your mind keeps tripping you up.

  8. Why not use the airframe of the Voyager, the Airbus A330, as the basis for a AWACS aircraft with some enhance maritime surveillance capability? Or use the airframe of the P-8 MPA. That would reduce inventory requirements.

  9. “Or use the airframe of the P-8 MPA.” You mean just like the E7 Wedgetail uses a Boeing 737 airframe??

    The E7 as operated by the RAAF (6 aircraft), South Korea (4) and Turkey (4) with its fixed array MESA radar is quite simply the most advanced AWACS aircraft in service with a proven track record in combat.

    And its avialable off the shelf with the development costs and delays already absorbed courtesy of the RAAF and Boeing.

    On deployment right now in the Middle East the E7 is regarded as “the platform of choice” by coalition forces with anecdotal reports of US strike groups deliberately delaying an operation to coincide with an E7 Wedgetail being on station.

    The protracted development of the E7’s advanced technology is well documented.

    Any attempt to build an AWACS on a European donor airframe would likely face the same technological challenges and development delays meaning at best an entry into service date a decade or more away.

    Can the UK afford to wait that long or will it throw good money after bad upgrading the E3 Sentry and end up buying E7s in the long run – a repeat of the Nimrod P8 saga?

    • If Europe wants to be an EU name to it then take all the gear from the E-7 and throw in in an A-320. Similar sized aircraft and specs, Just be fitting it to a European airframe with out having to redesign everything. EU gets there European name on it and an aircraft without the major delays and development costs.

      • I think Boeing and Northrop Grumman might have something to say about handing over their intellectual property to Airbus.

        Plus I think you are seriously underestimating the systems integration challenge in any case.

        But hey good luck with that. I’ll watch the development of the European AWACS with interest.

        • Not just systems integration. Aircraft skins aren’t very strong so they can’t just glue or bolt that big heavy chunk of radar onto the top of an Airbus something-or-other. They’d need to identify appropriate points on the actual framing to attach it and it’s quite possible that there aren’t any that have enough spare force transmission margins to accommodate it so they then need to look at strengthening those points, analysing where the transmitted force vectors will go, and then modify other structural elements to accommodate that. They then probably need to re-analyse flight characteristics to compensate for the extra top weight and pendulum effects and a whole lot more.

  10. time also we brought back a Bomber fleet perhaps 4 to 6.

    its all about capability and adding to our offensive and defensive options.

    Having the capability to fly at 55.000ft + beyond enemy lines and cause havoc strikes fear. Our Navy is small and a bomber fleet could help sink a frigate or carrier

      • Heavy bombers are only useful in uncontested airspace. The russian bear bombers buzzing our airspace are a useful PR stunt by Russia, but realistically in a war situation the typhoon squadron would make short work of the relatively slow and unagile bombers. Heavy bombers are only useful in a contested airspace where they are escorted by friendly fighters which in turn negates the long distance nature as the fighters would not be able to follow.

        • the points you make are fair. but with the tech and software available are incredble, our early warning systems are just as vulnerable..

          we need to up our game, our capability and inventory of options make us predictable imo.

          a modest fleet of what the Russians and US have can’t do us any harm..

          I want us to be self reliant and small steps in our military evolution will promote the need for our budget to be increased and lets face it they could ten fold if they wanted to imo

          across NATO

          The UK, France, Italy, Germany, Spain, Turkey etc could all agree in acquiring two each totalling 12, now that’s an asset not including what the US have..

          I’m all for it, will it ever happen, not likely.

          • With our resources, the money is better spent ease where. It’s like the constant t45 upgrade with strike length missile debate, it would be nice but is is a nice to have, and not a need (especially combined with the limited number of tomahawks we can afford).

            If I had to pick capabilities to add i would like considered are (thnking off the top of my head):
            Combat search of rescue
            Adding gunship role to A400m
            Heavier mortars, aligned with nato allies

            that is after the existing capability that needs enhancing first, like raw troop numbers.

    • Interesting, and you make a compelling case in an earlier equally interesting comment.

      I wonder how the cost of a Wedgetail compares with that of a P-8A. I ask that because the price mentioned in this article for updating the U.K. E-3Ds is £2bn and coincidentally £2bn is what we are spending to get 9 P-8As to plug the capability gap after the disastrous Nimrod fiasco. There would be a certain delightful symmetry to just go straight to Wedgetail, maybe even with possible uplift in numbers or money saved if the fleet is already appropriately sized, without running down some expensive maybe not blind but possibly sub-optimal alley first.

      I do note from the photos in the RAAF presentation that it looks as if these would be another plane not refuelable by our Voyagers. Is the range on Wedgetail (and P-8A) long enough for that to not really be a big issue?

  11. Perhaps the government could offer to purchase Aussie-built Wedgetails, possibly alongside CEAFAR for later batch T26s, as part of a deal were the Australians to select the Type 26 for their future frigate programme.

  12. Morning all
    Standard platform first: 737
    Training costs reduced (commercial offerings)
    Increase in number of qualified pilots and crew (single airframe type)
    Engineering costs reduced (airframe is standard)
    Logistics cost reduced (utilise same model as C-17 and River Joint)
    No upfront development costs for platform
    Mission System:
    Utilise WedgeTail system (UK Crypt)
    Shared training system with Australia (learn their lessons, utilise their training)
    Crew exchange early (Seedcorn crews now as E-3 reaches end of life)
    Install boom on 5 Voyager to enable full ubiquitous use of the air.
    Retire Sentinel and replace with joint UKUS platform, probably on 737 frame.
    These simple thing are all within grasp of MoD and RAF, it is all about their ability to think outside of the box.
    737 P-8 fleet based in Lossiemouth
    737 WedgeTail fleet based at Waddington
    737 “Sentinel” fleet based at Waddington
    Maintenance overalls down at commercial supplier
    Crew type certified training done at commercial supplier
    Engineers trained on aircraft by commercial supplier to full CAA ratings
    Lossiemouth to become P-8 hub for US and U.K. aircraft (Norway too)
    The list goes on but you get the idea.
    Remember the airframe is not the mission/weapon system, it just gets the effects system to where it needs to be.

    • Yep, makes sense, except don’t know of an ASTOR replacement on a B737 platform in the US inventory (Rivet Joint replacement). Do you?

      • My only thought was that with the Type 45s, new ground based radars and the F35, does the UK really need a bleeding edge AEW aircarft? Perhaps something cheaper, capable that slots into a mosaic of options might be adequate.

  13. A previous statement of combining a AEW and Air to Air platform is a really bad idea. High power radar vs fuel vapour = bigga boom!

    A number of other options should be put forward as well as the 737 airframe “Wedgetail.
    1. A swarm of locally controlled UAVs.
    2. AirLander10.

    The problem with either an air to air refueller, AWAACS, C2 or Sentinel type aircraft is that they are primary strategic targets and therefore a lot of the enemy’s effort will be made to ensure they are either destroyed or disabled.
    The solution is spread the load, whereby if one or two assets are lost it won’t make a major difference to the overall performance of the system. This is why a large number of drones would be highly beneficial.
    The only problem that using a drone would be the performance of the radar. If you could ensure all the signal processing is carried out via a “mothership” or ground site. This will take a tremendous load requirement off the UAV that it must produce. All the power can be put into the transmission of the RF waveform. To have the range that the Sentry E3D can produce i.e. 400km (plus) requires an enormous amount of power. However the AN/APY-1/2 can be described as a analogue radar as it cannot control its beam direction/height etc like a directional AESA radar for example. Further an AESA radar can get away with requiring less power for the same radiated distance, due to the multiplication effect. Realistically though, you still require a large aircraft that can generate significant amounts of power.
    You therefore have a choice either you use the UAV radar for long distance search, but with poor resolution or you use a shorter distance radar with good resolution. The mothership would need to control at least 5 UAVs via a secure datalink to ensure decent coverage.
    The Airlander option may be worth a visit as it can stay on station for a least a week. Not sure what an air to air missile would do to a airship? But, I would have thought it had better survivalbility then a pressurised fixed wing aircraft. Because of its size you wouldn’t be limited to say an S band radar, but also include higher frequency radars for better target resolution.
    Just a thought!

    • Or you use a very large number of UAVs and use them for look down search from very high altitude exclusively, where the ranges are not so extreme. Granted, you then have to bet on being above the enemy. With current technology, using lots of drones to scan at long range is unrealistic. The airship idea is interesting, I’m not sure what the energy generation on an airship is like for higher frequency radar, but I’m no expert.

  14. Morning all
    Just a final one.
    Look st the role the RAF are trying to fill, Defence of UK airspace is just one of those.
    Independently deplorable system platforms are required so the U.K. can operate with allies or independently globally.
    UAV’s and small airframe platforms are all good in the national defence local context but as a nation we have ambitions to operate as a P5, G7, G8, G20 and NATO worldwide influencer. To do that you need platforms that can operate in that context.

  15. I do like the idea of the Airlander hybrid air vehicle concept, but I don’t think it can operate at a height that can take it above the weather. The Airlander 10 has a published altitude of 20,000ft at a cruise speed of 80kn. Which I believe would make it still vulnerable to weather systems. However, it can generate over 50KW of electrical power which is sufficient for a system such as Saab’s Erieye AESA radar. Further it has an endurance of 5 days which not only would be a good AEW, C3 platform but also a good MRA.
    I think the Airlander is worth further investigation.

  16. okay this is a good one to think about as the UK, French and Saudi as amongst the last 707’s built and share the same basic design and features.

    The US and NATO AWACS are E3A type airframes and have older engines.

    as to the airframe as such please do not forget that we just bought 3 Rivet Joint aircraft and one of the arguments used was that we where already flying 707’s in the form of the AWACS.

    The two options out there from boeing are the 737 Wedgetail as used by the australians and or the 767 that Japan are using. However, I must go on record a stating that the 767 has the same basic mission systems as the 707 aircraft.

    other options are the Swedish and israeli business aircraft type AWACS or even the E2 Hawkeye.
    again we already have ASTOR which is a business jet AWACS aircraft and of course the P8 which is a 737 airframe.

    it is of course interesting to note that in the US AWACS in the older 707 AWACS have n new mission system all be it bolted to the original radar while the UK AWACS at its heart is two IBM 360 computers known as a 4 Pi ( 2 x 360).

    I think we need to take a very serious look at the whole surveillance issue and the availability of more but smaller business jet type aircraft.

    As to my own background i am ex-RAF and spent 5 years on the AWACS software team as well as 3 years on Nimrod MR2, 6 months on MR4, 3 years on ASTOR, 3 years on Watchkeeper and as far as i know i am, the only UK person who has worked in the UK on both the AWACS and the UK NAS ATC system which are derived from the same 1969 IBM 360 computer software in JOVIAL and hardware.


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