Pros and cons of various AWACS configuration

[helmutkohl]

In regard to AWACS aircraft, there's many different configurations these days

balance beams

dishes

bench

or stick them to the side

I was wondering what the general pros and cons were
given that technology has advanced, I would assume that something that uses mechanical? steering is no longer necessary, like those huge rotating dishes

in that sense wouldnt something like the bottom AWACs be preferable as it has less drag?
also what about aircraft carrier applications
does one configuration do better than others?

 

[red admiral]

Detection Range, Revisit Rate, Field of Regard and host platform size largely dictate this.

G550 CAEW is lowest drag impact but reduces fore/aft sector performance and kinda obviously Antenna height needs to be less than fuselage height. Otherwise stick it on top like Wedgetail.

 

[helmutkohl]

Detection Range, Revisit Rate, Field of Regard and host platform size largely dictate this.

G550 CAEW is lowest drag impact but reduces fore/aft sector performance and kinda obviously Antenna height needs to be less than fuselage height. Otherwise stick it on top like Wedgetail.

do you think the wedgetail's shape has made the more traditional circular dishes obsolete?
I am wondering why it hasnt been implemented on the E-2 yet (albeit a smaller one)

 

[bring_it_on]

The "Top Hat" end-firing configuration adopted by the Wedgetail was driven by a few factors. First, was to get 360 degree coverage that the balance beam designs in the AEW class (at the time) lacked. These still do (even SAAB's new design). The second was to get aerodynamic improvements that would allow a lower cost narrow-body based platform to meet some of the endurance requirements at the time possible through the use of larger more traditional AWACS like platforms. The drag and weight penalty of a large circular 'rotadome' or even a fixed circular array on the 737 NG would have limited its performance significantly. Finally, the configuration allowed full electronic scanning without the need to rotate the array thus saving a lot of weight, design penalties, and being able to set revisit rates better than a rotating design. So all in, they were looking at ways to get the performance that at the time was only available to the larger and more expensive platforms in a design that was only slightly more expensive than one based on a business jet.

View: https://www.youtube.com/watch?v=MEawZlOLJwc


Pros (Top Hat)

- Space and weight optimized for a 737 NG
- Lower drag than Rotadome
- Offers performance that can compete with much larger SWaP optimized platforms
- Electronic Scanning

Cons (Top Hat)

- Needed to go to L-band to meet detection and track performance range requirements (that may or may not matter)
- Was complicated, and troublesome to design and integrate (lots of pains in development that took years to solve)

The E-2 utilizes a UHF antenna that rotates (mechanical rotation combined with electronic scanning). The platform is size, and weight limited though a full electronically scanning (non rotating) upgrade is possible down the road now that technology has caught up allowing for that solution to be adopted within the SWaP constraints. I don't think you would be able to fit a L-band fixed top hat antenna on the E-2D and still have the platform meet its performance requirements while staying within the SWaP limits of the platform.

 

[apparition13]

There's also the PRC version of the dome: pack three AESA radars in a triangular configuration in a fixed (non-rotating) dome. I suspect this might give the most even 360 degree AESA coverage. I wonder why the E2D didn't go with the design.

In the CSA (common support aircraft) days Grumman (and others?) was looking into integrating AESA radars into wing and tail leading and trailing edges. They were pretty much invisible. I don't know how far they got, although I gather they were pretty confident they could get it to work. That would pretty much eliminate radar drag, even more than CAEW.

Personally I want to see someone stick Erieye on a V-22. Preferably with a couple more panels to cover the front and rear 30 degrees. UK, Italy, Spain, Australia, Japan, India, Brasil, even the USMC, could all use them off their STOVL (or STOBAR for India) carriers.

 

[red admiral]

do you think the wedgetail's shape has made the more traditional circular dishes obsolete?
I am wondering why it hasnt been implemented on the E-2 yet (albeit a smaller one)

I think its more about the radar technology itself leading to better potential installation schemes.

E.g. Fuselage side or "blade" means you can have a much larger antenna than in a rotodome for enhanced performance. But fuselage side on a 737 and the engines block a lot of field of regard.

E-2D was a lower risk tech update rather than change everything. Probably need a pretty high balance beam to clear the props and then raise/lower this on deck = extra mechanical integration risk

 

[stealthflanker]

There's also the PRC version of the dome: pack three AESA radars in a triangular configuration in a fixed (non-rotating) dome. I suspect this might give the most even 360 degree AESA coverage. I wonder why the E2D didn't go with the design.

Well They can but they need to change operational frequency into higher one like S-band.

Otherwise dividing the already small rotodome of the E-2 for the existing UHF frequency becomes nightmare as the resulting radar's beam might be too wide in azimuth due to reduced length of the antenna. This wide beamwidth worsen the angular resolution capability and in some extent reducing ranges as the gain become smaller due to less elements can be placed in that confines of space.

The existing E-2 already have worse elevation beamwidth of 20 degrees which makes it cannot resolve target altitude the same way as other AEW that works in S-band did. It instead have to use Multipath heightfinding technique which constrain the operational altitude, and may deny overland performance due to more variances in soil electrical properties.

In the CSA (common support aircraft) days Grumman (and others?) was looking into integrating AESA radars into wing and tail leading and trailing edges. They were pretty much invisible. I don't know how far they got, although I gather they were pretty confident they could get it to work. That would pretty much eliminate radar drag, even more than CAEW.

Yes they did, although they might not like the idea of thick wing so a proper vertical spacing for the antenna elements. if one line/linear elements is desired the Elevation beamwidth might be far bigger which entirely denies heightfinding capability. Or there might be weight penalty of having to install thick dielectric lens which made out of foam or even wood to help reduce the beamwidth in vertical direction.

 

[bring_it_on]

There's also the PRC version of the dome: pack three AESA radars in a triangular configuration in a fixed (non-rotating) dome. I suspect this might give the most even 360 degree AESA coverage. I wonder why the E2D didn't go with the design.

That's what was proposed by Raytheon and its Israeli partner for the Australian competition. Three equal sized L-band arrays each covering 120 degrees and not needing to rotate. This type of solution requires a significantly larger dome, with a weight and drag penalty that would be unacceptable for something like a 737 sized aircraft. If Boeing/Northrop had been playing with a 767 sized aircraft at the time, then the E-3's Rotadome configuration but without a rotating antenna would have been much simpler to design and implement. That they wanted to go after the economics of a NB airframe is what lead them to the tophat configuration, not to mention that the solution is scalable so even if you put it on a WB it will get you better airframe performance compared to a giant circular configuration that is larger, taller and has more drag.

When the E-2D was developed the hybrid (Electronic+mechanical scanning) was the most mature option. However, they are begining to fund some development to get to a fully electronically scanning (non rotating) array so that is the future for the platform.

UESA Revival Offers Dual-Band Radar For Future Early Warning Aircraft | Aviation Week Network

New testing shows that a 20-year-old concept can double the radiated power of future airborne early warning radars.

aviationweek.com

 

[Archibald]

Amazing thread, keep up the good work folks !

 

[red admiral]

That's what was proposed by Raytheon and its Israeli partner for the Australian competition. Three equal sized L-band arrays each covering 120 degrees and not needing to rotate.

Also kinda obviously three radars are more expensive than one radar...

 

[bring_it_on]

It uses three arrays which is also the case for the MESA antenna on the E-7 (The two side arrays and the top array) The balance beam designs utilize two arrays so there are probably some savings there. A rotating radar housed in a rotadome would be cheaper since it could use one array and rotate it at variable rates to cover 360 degree. But I don't see anyone accepting mechanical rotation in this day and age unless you have constraints like carrier ops etc. The ability to direct the power in certain sectors to get extended ranges, and to be able to revisit certain targets more frequently is too much to lose even if you have a high RPM design.

 

[red admiral]

I'd be pretty sure a single AESA in a rotodome with mechinical azimuth scan is still a good low cost option for many missions. You get 360 coverage when you want or can effectively just lock the rotodome in place and point the AESA in the direction of the targets. More flexible than your E-3 style rotodome.

I'd also be interested to see just jow useful the endfire fore/aft array on E-7 is, especially aft coverage through the fin... Definitely seems to me that the fore/aft fuselage radomes on the CAEW are preferable from a performance point of view.

 

[helmutkohl]

There's also the PRC version of the dome: pack three AESA radars in a triangular configuration in a fixed (non-rotating) dome. I suspect this might give the most even 360 degree AESA coverage. I wonder why the E2D didn't go with the design.

In the CSA (common support aircraft) days Grumman (and others?) was looking into integrating AESA radars into wing and tail leading and trailing edges. They were pretty much invisible. I don't know how far they got, although I gather they were pretty confident they could get it to work. That would pretty much eliminate radar drag, even more than CAEW.

Personally I want to see someone stick Erieye on a V-22. Preferably with a couple more panels to cover the front and rear 30 degrees. UK, Italy, Spain, Australia, Japan, India, Brasil, even the USMC, could all use them off their STOVL (or STOBAR for India) carriers.

same.. an awacs V-22 might be the one thing missing from making a stovl carrier nearly as effective as a catobar one.
while I do wish the QE went catobar..
part of me was always interested in how a larger size stovl carrier would handle.. the rolling landings now allow more bring back abilities
and the F-35B seems to be able to take off with quite a bit of load. pilot carrier qualification is easier and the landings are less stressing for the airframe compared to catobar. all that was missing was awacs

 

[bring_it_on]

I'd be pretty sure a single AESA in a rotodome with mechinical azimuth scan is still a good low cost option for many missions. You get 360 coverage when you want or can effectively just lock the rotodome in place and point the AESA in the direction of the targets. More flexible than your E-3 style rotodome.

The most popular 'low cost' or affordable option is going to be the balance beam mounted on a small aircraft. Simple to design and integrate on most platforms (often the budget customer also has constraints on how expensive the aircraft and conversion can be) and at S band you can get it on some fairly small and economical business jets as has been done by Sweden China, and India. The E-7 success in Australia, South Korea, Turkey, UK and soon the US basically did away with trying to figure out another option on a smaller NB aircraft. If you want 360 on a similar platform the tophat is going to be the most efficient way to get to that. Going forward, we'll see smaller business jets with a balance beam, E-7 and larger widebodies with electronic scanning non rotating arrays in a rotadome. I suspect that most of the AEW&C demands will fit into that. Perhaps some niche applications will consider a single rotating array as an alternative to a 240 degree balance beam, or a more expensive fixed array set up but that will likely not see as much success as the other options IMO. But unless you have carrier platform constraints it would be strange to pursue that option if you have affordability in mind. Lockheed didn't really have a lot of success in pushing the E-2 sensor on a C-130 for example.

 

[helmutkohl]

^ since weve seen the balance beam integrated on smaller aircraft.. like the Saab turboprop..
could it also be done on the E-2 or potentially the V-22?

 

[stealthflanker]

potentially the V-22?

This is interesting option. But might necessitating a large change in the main wingbox. It's now not only need to "carry" the entire engine + equalizing gears and be strong enough for that but also to carry the antenna structure and perhaps cooling plumbing to cool the AESA on top. If the wingstow mechanism from V-22 desired, it would potentially add more complexity.

 

[red admiral]

^ since weve seen the balance beam integrated on smaller aircraft.. like the Saab turboprop..
could it also be done on the E-2 or potentially the V-22?

Looking through the props/wings/nacelles is bad for radar performance unless the mounting is very high (and retractable for fitting in the hangar?)

The twist wing fold on V-22 makes it even harder.

 

[Jason Dykstra (Wyvern)]

What about something in the style of the Nimrod AEW?

From what I can tell, such a configuration gives better all-round visibility than a standard dish would at the time. Is this true?

 

[stealthflanker]

What about something in the style of the Nimrod AEW?

From what I can tell, such a configuration gives better all-round visibility than a standard dish would at the time. Is this true?

Yes, this is true. although ungainly. but yes it provides the best all round visibility, without being obstructed by airframe or disturbed by say, propeller modulations.

 

[Trident]

Beriev patented a very nice take on the conformal approach a few years ago:

САМОЛЕТ ПОНИЖЕННОЙ РАДИОЛОКАЦИОННОЙ ЗАМЕТНОСТИ ПАЛУБНОГО И НАЗЕМНОГО БАЗИРОВАНИЯ С СИСТЕМОЙ АНТЕНН КРУГОВОГО ОБЗОРА

Изобретение относится к авиационной технике и касается создания самолетов с системой антенн кругового обзора как палубного, так и наземного базирования для задач радиолокационного дозора и наведения (РЛДН), управления воздушным движением и морского патрулирования. Самолет пониженной...

edrid.ru

Seems really elegant, decently sized arrays with coverage that is both all-round and unobstructed. Neat aerodynamic integration too, though it is an open question just how well trading off wing aspect ratio for lower wetted area and interference drag would work. The buried engines might limit engine BPR, again a compromise between drag and SFC which is difficult to call.

 

[Trident]

Also kinda obviously three radars are more expensive than one radar...

You'd think so... but how true is that of AESA radars, where many components that would previously have been multiplied by antenna number are subsumed into the MMICs? Seems as though cost could nowadays scale more with the total number of TRMs rather than the number of distinct arrays.

 

[red admiral]

Seems as though cost could nowadays scale more with the total number of TRMs rather than the number of distinct arrays.

The TRMs / array are a large proprtional of the cost of an array, so basically cost does scale with array size/number of TRMs but not quite linearly.

My comment was more assuming the different layouts were aiming for similar detection ranges hence the single and triple arrays are similar size. The triple arrangement could give the same pwrformance with smaller arrays (reduced scan volume per array) but only if you havevenough power and cooling for all of them to be Tx at the same time.

 

[GARGEAN]

do you think the wedgetail's shape has made the more traditional circular dishes obsolete?

Absolutely no. Angular coverage is and will be needed, and that's not what Wedgetail can give.

 

[GARGEAN]

There's also the PRC version of the dome: pack three AESA radars in a triangular configuration in a fixed (non-rotating) dome. I suspect this might give the most even 360 degree AESA coverage. I wonder why the E2D didn't go with the design.

This one still has problems. First - antenna aperture is smaller than with single rotating array. Second - angular coverage suffers close to angles of arrays connection. Second problem can be alleviated by having four arrays instead of three, but then first problem will become even bigger.

 

[helmutkohl]

reviving this topic, but it seems that South Korea is now looking for a new AEW aircraft.
the final 3 candidates all sport different configurations
E-7 - Tophat
GlobalEye - balance beam
G550 - fuselage

note that Korea already uses the E-7A

 

[Scott Kenny]

I'd be pretty sure a single AESA in a rotodome with mechinical azimuth scan is still a good low cost option for many missions. You get 360 coverage when you want or can effectively just lock the rotodome in place and point the AESA in the direction of the targets. More flexible than your E-3 style rotodome.

I'd also be interested to see just jow useful the endfire fore/aft array on E-7 is, especially aft coverage through the fin... Definitely seems to me that the fore/aft fuselage radomes on the CAEW are preferable from a performance point of view.

IIRC, the tophat array is set to just barely clear the top of the fin and the fuselage when the 737 is in cruise.

Edit: I did NOT recall correctly. The tophat hits roughly the middle of the fin aft, but does barely clear the nose by a couple of degrees.

This one still has problems. First - antenna aperture is smaller than with single rotating array. Second - angular coverage suffers close to angles of arrays connection. Second problem can be alleviated by having four arrays instead of three, but then first problem will become even bigger.

Not that much smaller. A dome that can hold a 2m wide rotating antenna can hold a trio of 1.73m long antennas (give or take some rounding due to backing electronics mess). ~15% antenna width loss.

 

[red admiral]

IIRC, the tophat array is set to just barely clear the top of the fin and the fuselage when the 737 is in cruise.

No chance of the endfire array clearing the fin unless it's angled 60deg up and looking into space. Maybe ok over the nose against high altitude targets only.

For multiple AESAs within a fixed rotodome then this has performance advantages e.g. scan rate, but is obviously much heavier with more power / cooling and associated cost

 

[riggerrob]

One disadvantage of side-scanning radars is that they force the airplane to fly a predictable path. This gives defenders a rough idea of what they are watching and also helps time interceptors to shoot down that pesky AWACS.

 

[riggerrob]

Belly mounted radars were first installed in Lancaster bombers during WW2. They were primarily used to locate targets at night. That worked okay until the Luftwaffe figured out which frequency they were broadcasting, then used those same signals to home in on those pesky bombers.
During the 1940s and 1950s, belly-mounted radars were installed on Shackletons, AD-1 Skyraiders and Fairey Gannets. Note that all three bombers already had long landing gear legs.
Fast forward to 1he 1982 Falklands War and the (British) Royal Navy rushed into service an AWACS version of their Sea King helicopters. They hung a half-spherical antenna out the cargo door and retracted it up for landing and down for scan. Since Sea Kings have a service ceiling of only 14,700 feet and endurance of around 4.5 hours. I suspect that altitude limited radar range. Anything above 5,000 feet and you need to consider adding supplemental breathing oxygen for crew-members. Note that night vision can deteriorate at cabin pressure altitudes as low as 5,000 MSL.

A similar radar semi-sphere is now installed on a few Merlin helicopters. Merlin has a similar service ceiling of 15,000 feet and endurance of 5 hours
.
For an airframe as complex as CV-22 Osprey, I suspect that they will install a similar retractable radar half-dome on the cargo ramp under the tail. CV-22 has a service ceiling of 25,000 feet and endurance of up to 6 or 7 hours.

 

[Scott Kenny]

No chance of the endfire array clearing the fin unless it's angled 60deg up and looking into space. Maybe ok over the nose against high altitude targets only.

You're right, I had misremembered how tall the fin was on the Wedgetails. For some reason my mind had the array also clearing the top of the fin.

Belly mounted radars were first installed in Lancaster bombers during WW2. They were primarily used to locate targets at night. That worked okay until the Luftwaffe figured out which frequency they were broadcasting, then used those same signals to home in on those pesky bombers.
During the 1940s and 1950s, belly-mounted radars were installed on Shackletons, AD-1 Skyraiders and Fairey Gannets. Note that all three bombers already had long landing gear legs.
Fast forward to 1he 1982 Falklands War and the (British) Royal Navy rushed into service an AWACS version of their Sea King helicopters. They hung a half-spherical antenna out the cargo door and retracted it up for landing and down for scan. Since Sea Kings have a service ceiling of only 14,700 feet and endurance of around 4.5 hours. I suspect that altitude limited radar range. Anything above 5,000 feet and you need to consider adding supplemental breathing oxygen for crew-members. Note that night vision can deteriorate at cabin pressure altitudes as low as 5,000 MSL.

Dude, I live at 5000ft MSL. No supplemental oxygen required till 10k.

Maybe the RAF and RN need to recruit more Highlanders and Gurkhas, folks who grew up at over 5000ft.

For an airframe as complex as CV-22 Osprey, I suspect that they will install a similar retractable radar half-dome on the cargo ramp under the tail. CV-22 has a service ceiling of 25,000 feet and endurance of up to 6 or 7 hours.

As I have been reminded a lot, the Osprey is not pressurized. The crew would have to be on oxygen for their entire mission.

 

[BlackBat242]

And that idea has also already been examined - and rejected.

MV-22 TOSS (upper image from April 2008):

 

[timmymagic]

Belly mounted radars were first installed in Lancaster bombers during WW2. They were primarily used to locate targets at night. That worked okay until the Luftwaffe figured out which frequency they were broadcasting, then used those same signals to home in on those pesky bombers.

I think you're confusing H2S with the Monica tail warning radar....

German's didn't home in on H2S or H2X. But they did home in on Monica using the Flensburg passive receiver...whats often missed though is the RAF got 18 months of use out of Monica before the German's developed Flensburg, but even then only a small number of aircraft were fitted with Flensburg. 18 months of a useful system before a partial countermeasure was developed was very good going for WW2.

As it turned out the German's only got around 5 months of use of Flensburg as they rolled it out on their aircraft as a JU-88 G-1 got confused and landed at RAF Woodbridge....the RAF immediately realised what it was and orders were immediately given to RAF Bomber Command crews to switch off Monica permanently. The RAF very shortly after introduced the Automatic Gun Laying Turret with a new radar that was in practice used as a tail warning radar the majority of time and wasn't picked up by Flensburg...Action...Reaction....

Whats surprising is that the RAF were doing the same trick to the Luftwaffe using Serrate equipped Mosquito homing in on Liechtenstein equipped German night fighters from 1943, when the German's worked out what was going on the RAF moved to using Perfectos equipment that triggered German IFF and allowed homing...

 

[MrTopaz]

And that idea has also already been examined - and rejected.

MV-22 TOSS (upper image from April 2008):

View attachment 743298

View attachment 743299

It would have been cheap, though. You can usually buy those things at any gas station, and they slip right onto your trailer hitch.

 

[stealthflanker]

And that idea has also already been examined - and rejected.

MV-22 TOSS (upper image from April 2008):

View attachment 743298

View attachment 743299

Kinda obvious why, beside pressurization which can allow the aircraft to reach higher altitude. Thus more coverage, it also lacks crew accommodation.

AEW mission are taxing manpower wise, staring into scopes for hours will induce fatigue and boredoom. It will limit the endurance of the AEW.

 

[Cordy]

I'm sure AWAC aircraft have some advantages, but would have thought survivability now questionable due the threat of equivalent AIM-174Bs, would not numerous constellations of hundreds/thousands of low cost LEO micro satellites be more survivable e.g. Google saying 6,400 Starlink satellites now in orbit.

 

[EwenS]

I think you're confusing H2S with the Monica tail warning radar....

German's didn't home in on H2S or H2X. But they did home in on Monica using the Flensburg passive receiver...whats often missed though is the RAF got 18 months of use out of Monica before the German's developed Flensburg, but even then only a small number of aircraft were fitted with Flensburg. 18 months of a useful system before a partial countermeasure was developed was very good going for WW2.

As it turned out the German's only got around 5 months of use of Flensburg as they rolled it out on their aircraft as a JU-88 G-1 got confused and landed at RAF Woodbridge....the RAF immediately realised what it was and orders were immediately given to RAF Bomber Command crews to switch off Monica permanently. The RAF very shortly after introduced the Automatic Gun Laying Turret with a new radar that was in practice used as a tail warning radar the majority of time and wasn't picked up by Flensburg...Action...Reaction....

Whats surprising is that the RAF were doing the same trick to the Luftwaffe using Serrate equipped Mosquito homing in on Liechtenstein equipped German night fighters from 1943, when the German's worked out what was going on the RAF moved to using Perfectos equipment that triggered German IFF and allowed homing...

The Germans did have a device for homing on 10cm radars like H2S and providing warning for various ASV sets operating on the same wavelength. It was called Naxos with versions for fitting in both aircraft and on U-boats. It was not effective for detecting 3cm radars like H2X and similar ASV sets that entered service around mid-1944.

Naxos radar detector - Wikipedia

en.m.wikipedia.org

 

[timmymagic]

The Germans did have a device for homing on 10cm radars like H2S and providing warning for various ASV sets operating on the same wavelength. It was called Naxos with versions for fitting in both aircraft and on U-boats. It was not effective for detecting 3cm radars like H2X and similar ASV sets that entered service around mid-1944.

Naxos radar detector - Wikipedia

en.m.wikipedia.org

They tried homing but couldn't get anything more than a general location, but it was useful as a detector, particularly on the U-Boats.