Sunday, January 24, 2016

Unmanned Aerial ASW

One of the common ideas for future ASW operations is to use unmanned aircraft.  However, I have seen no detailed discussion of such a UAV and there are significant problems associated with the concept.  More generally, there is a tendency, now, to simply say “unmanned” in response to every military problem or function and then consider the discussion finished, as if unmanned is the automatic and complete solution to everything.  Diversity is the same way – you say “diversity” and all further discussion stops.  No one bothers to question whether diversity actually offers any inherent benefits.  But, I digress …

Is unmanned aerial ASW feasible?  Is it effective?  Is it cost effective.  Is it …?

Let’s take a closer look at surface ship unmanned aerial ASW possibilities.

One of the key benefits is that the ASW-UAV is presumed to be significantly smaller than the standard SH-60 type helo and, therefore, more aircraft can be carried by a ship thus expanding ASW coverage.  This would certainly be true if the smaller ASW-UAV carried the same amount of sonobuoys, dipping sonars, torpedoes, comm gear, MAD detectors, radar, etc. that the SH-60 does.  Unfortunately, herein lies the first problem with ASW-UAVs – they’re small.  They can’t carry the same load of gear.

Let’s look at the Navy’s standard UAV, the Fire Scout MQ-8B, which would, presumably, be the UAV of choice for the surface ship ASW-UAV role.  Here are some publicly cited weights of interest.

Payload = 600 lb
Empty Weight = 2073 lb
Max Takeoff Weight = 3150 lb

So, we’ve got a 600 lb payload to work with.  What does ASW gear weigh?  Here’s some weights for the common torpedoes used in ASW.

Mk46 = 508 lb
Mk50 = 800 lb
Mk54 = 608 lb

We see, then, that the Fire Scout’s entire payload is consumed by a single torpedo.  But wait, don’t we need dipping sonars and sonobuoys and radars and other stuff?  Here’s some weights for the sonobuoys.

Sonobuoys = ~20 lb each
Sonobuoy Launcher  = ~8 lb each

So, for a load of, say, 24 sonobuoys, that equates to 672 lbs and that’s without any of the supporting electrical, power, computer, and comm gear needed to actually operate the sonobuoy launch system.

MQ-8B Fire Scout

 All right, we can see where this is going.  I won’t even bother to cite weights for MAD gear, radars, etc.  The MQ-8B Fire Scout clearly isn’t going to be able to carry an entire ASW equipment fit.  The MQ-8B’s successor, the MQ-8C, however, is much larger so maybe it can carry the necessary equipment.  Here’s a few pertinent spec’s for the “C” model.  The “C” is based on the Bell 407 model, by the way.

Length = 41 ft  (24 ft for MQ-8B)
Rotor Diameter = 35 ft  (27 ft for MQ-8B)
Max Weight = 6000 lb
Payload = 500 lb

Despite being larger, the payload is actually a bit smaller than the “B” model.  On the plus side, the base “C” model, in its commercial Bell 407 version, is capable of carrying a 2,560 lb external sling load.  Although that doesn’t help as far as mounting ASW equipment it might offer the possibility of carrying torpedoes.

Regardless of the exact payload, the problem with the “C” model is that it isn’t all that much smaller than a full size SH-60 helo.  Here’s some dimensions of the SH-60 for comparison with MQ-8B/C values in parentheses.

Length = 64 ft  (41 ft for the “C”, 24 ft for “B”)
Rotor Diameter = 53 ft  (35 ft for the “C”, 27 ft for the “B”)

Clearly, the “C” isn’t going to gain us multiple airframes in the same space as the SH-60 as UAV proponents like to claim.

MQ-8C Fire Scout

 Another claimed benefit is endurance and, like all unmanned vehicles, can potentially offer greater endurance by eliminating the crew fatigue issue.  However, also like all unmanned vehicles, endurance does not eliminate mechanical issues.  Aircraft, whether manned or unmanned, suffer from mechanical issues and it is often these problems that wind up limiting an aircraft’s endurance especially for helos and especially for aircraft operating in a more stressful environment such as rapidly changing speed, direction, and altitude, as an ASW helo would, and operating close to the water surface and subject to wind, spray, fog, rain, etc.  Extremely high endurance UAVs, in contrast, operate at high altitudes, above the effects of weather, at constant speeds, and with little maneuvering – a much less mechanically stressful environment.

Endurance is also limited by equipment quantities.  For instance, if we want to use an ASW-UAV for 8-12 hours of continuous ASW coverage we would need to include a sizable quantity of sonobuoys – far more than an SH-60 typically carries.  That increases the weight and requires more space which means the UAV must be larger, thereby negating the UAV small size benefit.  Conversely, if we want to keep the UAV small then it will have to return to the ship for reloading of sonobuoys on a more frequent basis, thereby negating the endurance benefit.

So, where does this leave us?  We can design an unmanned helo to carry all the requisite ASW equipment but the resulting size will push us back near the manned SH-60 helo and won’t gain us the several UAVs per ship that would offer the potential for greatly expanding our ASW coverage.

Alternatively, we could design small UAVs that would each carry a single “function” of the ASW fit.  For example, one UAV could carry sonobuoys, another could carry MAD and a dipping sonar, and one could carry the anti-submarine torpedoes.  This should sound familiar, by the way.  You’ll recall that the Drone Anti-Submarine Helicopter (DASH) of the early 1960’s carried a single torpedo or depth charge and was used as a weapons transport platform to attack a target located by the host ship.

The problem with splitting the ASW equipment among multiple UAVs is that now multiple UAVs are required to perform the complete ASW operation on a single target.  Again, this won’t result in a net increase in ASW aircraft or coverage.

Finally, communications are a persistent problem for UAVs.  They have a disturbing tendency to wander off, never to be seen again.  The problem will be exacerbated operating just off the surface of the water.  At those altitudes it is unknown how far effective control comms can be maintained.  It may not be possible to control an ASW-UAV at useful distances from the host vessel.  Of course, operating in an electromagnetically challenged environment may also preclude effective ASW-UAV operations.

In summary, ASW-UAVs are a potentially beneficial concept.  Eliminating crew fatigue as a limiting factor on endurance is a tremendous potential benefit.  Smaller UAVs offer the possibility of expanding ASW coverage.  The practical problems, however, do not seem readily solvable at this time.  This is a concept well worth pursuing as a developmental effort but I do not see a practical use in the near future.


  1. Helicopters don't really have the endurance to outlast the human element, and no major load penalty for the human element as per altitude g ect... Considering that the UAV only real benefit over a existing human ASW platform is pilot safety the negatives far outweigh. UAV are good at the mundane but will not be able to replace a human in the loop in ASW.

    A UAV that could be useful in my opinion would be small with a built in sonar suit with a duck form. It would fly out ahead land and start pinging sending the data back until told to return fuel then again go forward if moving or just float on station if not. Basically a self deploying reusable bouy small enough to be carried in enough numbers, with enough range to build a bubble around X ship or convoy. Something like the proposed amazon package delivery system beefed up easily carried in the corner of the bay in double digits. Leave the torpedoes to something else, the standard helo or even maybe something faster like the proposed tail sitter.

    A not much spoken but serious threat is the anti air missiles that are starting to proliferate the modern subs. If a convoy only has a handful of helos to begin with, considering only a few can deploy at any given time a sub can close with intention to kill the helo and so cutting a huge gap in the defense screen.

    UAV's real benefit is that if built cheep small numerous they can turn the defense/offense cost curve not like a shark but as Parana. Parana small fish but so numerous you cannot kill them all and your only hope is to flee. Saturation of overwhelming numbers.

  2. I am not sure where you got data on MQ-8B/C. There is a lot of conflicting, incomplete info. The only official data I've seen from Navy is comparing endurance with a constant internal payload of 300 lbs.

    - 5.5 hrs (standard day
    - 4.5 hrs (hot day)
    - 12.0 hrs (standard day)
    - 10.0 hrs (hot day)

    The Northrop Grumman brochure lists 500 lbs internal payload. Presumably that is a structural limit.

    External payload (i.e. hardpoints) is not directly addressed but it does say sling payload of 2,600 lbs are possible on Bell 407. I would think that means you should be able to hang 'something' externally if needed although obviously not 2,600 lbs.

    To your point on ASW sensors. It depends on what functions you want. Miniaturization has come a long way even since the MH-60R was developed. There are very lightweight sensors available if Navy wanted them.

    The first link below shows a proposed mini-Magnetic Anomaly Detection (MAD) system that weighs less than 10 lbs. The second link shows a concept for a mini-sonobuoy that is 1/16th the size of current (2-3 lbs).

    ASW weapons are the obvious challenge, since even the lightweight torpedo would be hard to carry on MQ-8C. But then again maybe you don't need the MQ-8C to do the whole kill-chain.

  3. how you doing NavyMatters? I accidentally noticed you got credit at
    Would Britain Really be Back as a Traditional Carrier Power?
    OT here, just thought you might like it :)

    1. Thanks for the heads up. Always nice to be noticed!

    2. NavyMatters: what's your email? thought it'd be at
      but can't see it there, thanks

    3. BC, due to the crazies and idiots out there, I don't make my email generally known. Was there something you wanted to send me?

    4. Big Carambole, check your email.

    5. Big Carambole, for your protection, I deleted your comment due to the personal information contained in it.

  4. Hi ComNavOps,

    I'm the author of the British carrier piece. Been following your blog regularly and must say the material here is top notch. Keep posting!


    1. Ben, thanks for stopping by. I've read that piece - very nice. I'm honored to be of use to you. Let me know if you have any desire to do a guest post here or if I can help you in any way.

  5. A fire scout with a thales dipping sonar (267 kg) and a lightweight MAD sensor (1.5 kg) would be immensely useful as a supplement to regular ASW-helicopters.

    It would fly around and dip the sonar in a preset pattern, making a single ping in each location and record the echo. After a pre-set number of pings it would rise above the horizon (if neccessary), and transmit all accumulated and time-stamped recordings to the operator via vhf.

    Sonar buoys and torpedos are better left to human operators and larger aircrafts.

    1. Interesting. Which model are you talking about? I've seen a couple of models but they have a somewhat higher weight (306 kg). Also, it's not clear to me what that weight includes. Does it include power equipment?

      It's also not clear to me that these models have the capability to store and transmit data. They seem to be geared towards realtime display of data at operator stations on the helo.

      Finally, it's not clear to me that they can be operated in a fully automatic mode. They seem to offer user interaction features like beam steering, frequency selection, etc.

      So, it's not clear that they can be stand alone, fully automatic systems. It kind of looks like they're not set up for that. If not, it probably wouldn't take a huge effort to make them fully automatic but that would eliminate some of the interactive features and reduce the performance.


    2. "... it would rise above the horizon (if neccessary), and transmit ..."

      If you're searching for subs closer than the horizon, you're in serious trouble!!!

    3. The sensors are CAE's MAD-XR and Thales Flash Compact. The latter includes a medium frequency transducer, 300 meters of tether, an automatic hoisting system (electrical or hydraulic), and a serial interface. And yes, it can do a lot of fancy things, that you would rarely need on an UAV, but I think that if you try to make a drone with the capabilities of an asw-helicopter, you will just end up with a remote-controlled asw-helicopter.

      The point of an asw-drone should be to offload some of the repetetive and monotonous taske from the dedicated helicopter, not to replace the real helicopter. The helicopters on a frigate or a destroyer are in very high demand, and they are often worked hard when they are available.

      I definately prefer the smaller 'B' version of the fire-scout.

    4. I can't find a spec on the weight for that model. Where did you get the weight?

      The Thales product brochure makes it clear that an operator station is part of the product which, again, leads me to believe that there is no data storage and transmission capability. At the moment, this does not seem suited to an unmanned application. Again, though, it wouldn't take much to make it so.

    5. "... not to replace the real helicopter."

      And that's the key. Now, the question is whether you can obtain enough performance to justify the breaking up of the integrated, manned helo.

      Also, the ONLY demand on an ASW helo that matters is ASW. Everything else should be fill-in work and if the ASW helo det is doing their job and being used properly, there shouldn't be much fill-in time available. Sadly, this isn't the case. The reverse is true. Most of a helo's time is spent doing mundane, non-warfare tasks to the detriment of ASW.

      Excellent point.

    6. This comment has been removed by the author.

    7. UAVs are almost a zero sum game. If you add a UAV to a surface ship, you almost have to subtract a standard helo because the size difference isn't that great. Consider a ship with a capacity of two SH-60s. Now, we want to add a MQ-8B/C to do as you suggest. That means removing one SH-60 in order to have sufficient hangar space. Could we add a second MQ-8B/C? Maybe, maybe not but let's say yes. So, now we've moved from two fully capable SH-60s to one SH-60 and two MQ-8s capable of only a single, limited function. Has the overall ASW effort improved? Doesn't seem like it. In fact, it seems like that makes it worse.

      Your suggestion for the mode of use of the UAVs is not unreasonable but the size/hangar constraints don't work well. Now, if we could sacrifice one SH-60 and gain 6-8 UAVs that might well be a net gain but that's not currently feasible.

      Do you have any evidence to support your supposition that MQ-8B/Cs are significantly cheaper to operate? They're both helos. I'd be surprised if there was a significant difference but maybe there is.

    8. This also suggests that a small ASW-UAV carrier might be useful.

    9. This comment has been removed by the author.

    10. Smitty, I've seen those sets of numbers and never understood what they were. $5284/yr (=$14/day) is not the amount it costs to operate and support an MH-60R. Nobody believes it costs only $14 per day to operate and support an MH-60!

      Do you understand exactly what that number means? If so, explain it to me.

    11. This comment has been removed by the author.

    12. Ah, OK. That's in the realm of plausible. There's also some semblance of logic and scalability. The Fire Scout is "half" the size of the XH-60 and the cost is "half".

      Back to the main point ... I'm doubtful that we could get enough enhanced performance out of, say, two Fire Scouts to justify the loss of a single, full function SH-60.

    13. This comment has been removed by the author.

    14. The cost in this issue is irrelevant to me. It's all about performance. For a surface ship that can carry an SH-60, we'd have to sacrifice one helo to gain two Fire Scouts, at best (I'm doubtful that a Burke hangar could accommodate two FS and a SH). Even if both FS could operate without ever returning to the ship, would their single function increase the overall ASW performance compared to two SHs? I'm doubtful.

      Also, I'm doubtful that a FS operating a dipping sonar could conduct 10-12 hour missions. The fuel usage in hover mode is high. My barely educated guess is that they'd be lucky to get half that endurance. Regardless, the point is that the overall impact on ASW is probably negative.

      I don't see UAV-ASW as being viable from surface ships. As I said, a small UAV-ASW carrier might be a useful thing to have.

    15. This comment has been removed by the author.

    16. It doesn't matter if it's free to acquire and operate a FS. My concern is that there is no arrangement in the specific scenario I postulated (surface ship ASW) in which the capabilities of a viable combination of UAVs exceeds or even equals the capabilities of two SH-60s. I can't make the premise any simpler than that. Until someone can make a case that the performance of some UAV combination is sufficient, costs don't matter. If someone can make a case for the performance then we'll look at costs. Costs don't matter if they can't do the job.

    17. Cost may not matter to you, but it matters a lot to the folks who make decisions.

      The way I see it:

      - If the Falklands are any guide, surface ship sonars are going to generate a large number of contacts. Both real and false.

      - Looking at a standard one helo det, there are probably going to be more contacts to investigate than manned helos has flight hours.

      - I could see a scenario where a manned helo and its crew are launched so frequently to investigate contacts that they are worn/broken before finding their first real contact.

      - A persistent UAV system which could be kept airborne to help localize and confirm/dismiss surface ship sonar contacts could be very useful.

      - Persistence is critical. You want to keep the VTUAV as light as possible to maximize endurance, so that is there when needed.

      - Example: a VTUAV with MAD and a passive buoy to localize and classify the contact before bringing in the (more capable) manned helo.

      - This would saves flight hours and aircrew wear on the manned helo for when it came time to complete the Kill-Chain.

  6. UAV Sonobuoys R & D by Ultra Electronics

    Ultra is developing a new family of miniature passive sonobuoys that could be eventually deployed from UAV.

    The new 12"x 4.875" F sonobuoys use the company’s new multi-static technology, which assesses data from other sonobuoys and other energy in the water to provide an increased probability of detection. The sonobouys retain the same standard sonobuoy diameter but are two-thirds shorter than the 36 inch-long sonobuoys used by the P-8 Poseidon and P-3 Orion maritime patrol aircraft.

    The lighter sonobuoys could pave the way toward the development of a sonobuoy pod that could be fitted to a medium-sized UAV. Company literature shows a pod developed by Northrop Grumman to carry sonobuoys fitted to a Global Hawk platform.

    Ultra envisions a pod fitted with 12-36 small sonobuoys.Ultra envisions a pod fitted with 12 to 36 small sonobuoys. Inside the pod would be a buoy data receiver, processor and datalink system so information from the sonobuoys could be sent back to operators, opening the way for a UAV-based anti-submarine warfare capability.

    The company says it is working with a number of UAV producers on the project. The capability could be featured in the planned Unmanned Warrior demonstration, which will be part of the larger NATO multinational Joint Warrior exercise off the Scottish coast in 2016.

    Write up


    1. Nick, do you see the weakness in the concept? It only allows a single function to be performed and requires an entire airframe to do it. ASW involves multiple detection methods and this is only one. What about dipping sonar, MAD, radar, etc.? Will we need a dedicated UAV for each function? That would require more airframes and more hangar space than we use now. Where's the benefit?

      The problem is that each of the ASW "pieces" is being developed in isolation, devoid from an overall ASW methodology.

      I don't know what the overall answer is but someone more knowledgeable needs to develop an answer. Is UAV ASW the future? If so, someone needs to explain how it will work, not just develop isolated pieces that don't fit together.

      These companies are developing isolated bits of technology in the hopes of selling them to a UAV infatuated military. They are not focused on an actual warfighting solution. It's understandable but it means that the military needs to maintain the overall picture and not buy isolated bits that don't help.

      Does that make sense?

    2. A modern MAD is extremely light. On the order of 30 lbs.

      A Fire Scout with a MAD for investigation of ship sonar contacts actually makes a lot of sense.

      Would it be as effective as an MH-60R? Absolutely not. But maybe it doesn't need to be.

      It would provide a persistent localization capability, which is something we don't have with a single helicopter.

    3. A MAD detector is an extremely short ranged sensor (tens to hundreds of feet, at best). It's not generally used for detection but for confirmation. MAD-UAVs would have no hope of finding subs as far as I understand the technology.

    4. I am no sure you understand the difference between detection and localization.

      Surface ship sonars are used for initial detection. Helo sensors (MAD, dipping sonar, buoys) are used to localize/confirm target. It's collaborative effort.

      If our surface ship sonars are as effective at detection as Navy says they are, they are going to generate a lot of contacts. Real ones and presumably a bunch of false ones too.

      We are going to need something which can be there quickly to investigate and confirm. Helos with dipping sonars are certainly effective, but they can only be airborne 2-3 hrs at a time.

      A long-dwell UAV with a localization sensor would be very useful. We're not talking about initial detection. We're talking about a pouncer.

  7. Totally agree.

    Though as both helicopters and UAVs are constrained by weight and size, it is welcome news that progress is being made in payload numbers.

    Always think the tendency is to undervalue quantity over sophistication, and due to the high cost the loss of the limited numbers available may lead to total collapse, prime example being the 100,000 ton CVN Ford, for the same dollars you could procure three conventional 70,000 ton carriers based on cost of the RN QE2.

  8. Let’s not make the assumption that an ASW UAV to fly from surface combatants must be a helicopter.

    Instead, I think an unmanned version of the Icon A5 light amphibious sport plane (or similar), with sonar (dipping or fixed) and comms added, could make an intriguing ASW asset.

    Endurance could be very long, sitting on the surface and listening. (Maximum wave heights for takeoff and landing could be a limitation.)

    To keep things light and simple (and thus cheap and high-endurance), this UAV would be unarmed. Prosecution of detected contacts would be handled by firing off an ASROC from the nearest ship (another reason all Navy ships should have VLS, but that’s another topic), or calling in an MH-60 or P-8 to drop a torpedo.

    The A5 already has folding wings. It potentially could be deployed into the water from any surface combatant flight deck (with the addition of a lightweight crane), LCS stern ramp, amphib well deck, or remote minehunting system side door (on the Burkes so fitted). Or, sacrifice an RHIB and use its davits to store and deploy the UAV.

    If I understand C-Low correctly in the first comment, he is thinking along similar lines.


  9. i think we're looking at this wrong.
    Much like UAV use by ground forces, the assets utility is primarily in intel gathering, not strike. Strike costs great weight, but for strike we already have plenty of delivery methods, its the intel gathering, loiter ability, which is where UAV's have revolutionised the ground war fighters ability.

    Transpose that to the naval assets. You dont need to carry whopping great torpedoes with you everywhere you go.
    You need to carry detection gear. And not the full version either, not the processing unit, not the analysis hardware, merely the end point detection unit.
    So a very basic endpoint dipping sonar system, light buoys, etc. Signal detected transmitted to parent/host vessel, which are all already configured for the signal interpretation, (they've got their own sonars) and processing, C&C is already done on those platforms, and they carry a great deal of ordinance. Anti Sub missile/torpedoes with range in the hundreds of kilometres already exist, i know the Eeuros and Russians use them, fairly sure US has similar assets?

    1. Nate, you may have missed the main point from the post. The problem is that the UAVs can only carry a very limited amount of payload and yet will displace a full size, full function, standard SH-60 helo. This is a very bad trade unless you gain several UAVs per displaced helo and, as I pointed out in the post, this is not the case. There's only so much room in the hangar.

      As an aside, the Mk46/54 torpedoes, the Navy's standard anti-sub weapon, has a range of only 12,000 yds (~12 km) rather than hundreds of km.

    2. I didn't miss that at all friend.

      A. Im referring to the smaller platforms sighted, not the full sized unmanned variants of existing designs. 300kg carrying capacity should be plenty, as regards carrying listening gear.

      Torpedoes, I'm talking about an ASROC plus system. Torp strapped to a rocket or turbojet engine to get it to where the UAV is. Range of a few hundred Kilometers. Not proposing the world, these are existing technology but yes, new platforms will need to be designed to make UAV's work as ASW platforms.
      No, simply sticking an unmanned version of a currently manned helicopter wont do jack for ASW abilities of a ship.
      Check out AirMule, its legs are too short but its in dev. Something like that, which already has the carrying capacity, and is very small, and can be carried in large numbers on even something as small as an ASW frigate,
      That would be useful, provided you can get the surface combatant to be the launch point for the weapons and the Central hub for the ASW effort.
      Central brain/ordnancestore to a web of detection platforms.

    3. I checked out the AirMule. An interesting vehicle but the same problem exists. It's 20ft x 11ft which makes it half the size of a standard, full function helo. Thus, we could get two to fit in the hangar in place of a standard helo. Are two limited function UAVs going to offer an improvement in ASW performance over a single full function ASW helo? I don't see it. Unless we can get numbers up in the 6-8:1 replacement range we'll wind up decreasing our ASW capability instead of improving it.

    4. I think you need to closely consider the use case of ASW helos. An ASW doesn't really do the whole kill-chain. It's mainly used to react to cueing generated by is host ship's sonar.

      There is a report US Navy did on the Falklands which showed RN helo crews were run ragged just investigating all the contacts (real/false) being generated by their ASW destroyers.

      If you had a persistent UAV that could fill that contact investigation function, you could save a lot of wear and tear on the manned helo. Use the UAV to localize detections and confirm/deny presence of real targets.

      The upshot might be having more helos available for when you find a "real" target you need to kill. I'd imagine enemy subs don't like facing multiple dipping helos.

  10. You're thinking 2 dimensionally, your helo is 18 foot tall. The air mule is 7 foot tall with fans deployed. Even by your metric thats 4 vehicles in the space of one helo. And again, thats thinking latterly.
    You could stack them on end, or vertically, etc. Unmanned just opens a lot of doors traditional aircraft simply don't.

  11. Thank you for acknowledgement of the cold war DASH system. FYI & FWIW, the QH-50Cs we flew from Vogelgesang (DD 862) carried two homing torpedoes. The NDC was never released for service/deployment. An excellent source of valid DASH info is; It is maintained by Peter Papadokis (sc?) son of the inventor.


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