Thursday, June 25, 2015

Pegasus Class Hydrofoils

Ever the historian, ComNavOps likes to re-examine ships, tactics, and campaigns to glean lessons learned.  In that vein, let’s take a look at the remarkable Pegasus class hydrofoils (PHM, Patrol, Hydrofoil, Missile).  These vessels are often cited as possible alternatives or adjuncts to the more conventional fleet assets.  Here’s a quick reminder of their characteristics.

PHM (Patrol, Hydrofoil, Missile)

Number:                   6
Cost:                        $870,000 each (1)
Service:                   1977 – 1993
Length:                    132 ft
Displacement:          240 tons
Speed, hullborne:    12 kts
Speed, foilborne:     48 kts
Sensor:                    Mk92 Mod 1 Fire Control
Armament:               8x Harpoon, 76 mm Oto Melara gun
Propulsion:              1 GE gas turbine (foil) and 2 diesel (hull) with water jets
Range:                     750 nm – 1200 nm, depending on propulsion mix
Draft:                        7.5 ft (foils raised), 23 ft (foils lowered)

For their size, the vessels had good range and excellent seakeeping with an ability to maintain high speed in high sea states.

The PHM was a bit of a pet project of then CNO Zumwalt.  The PHM was to be part of the hi-lo mix concept being championed by Zumwalt.  Costs were an issue, apparently, although the degree of unconventionality may have largely contributed to the price tag.  Regardless, upon Zumwalt’s retirement, funding was redirected towards more conventional ships and the project languished until Congress intervened and forced completion of six of the vessels.

The PHM program was originally envisioned as a NATO response to the numerous Warsaw Pact missile boats and included plans for around 30 ships and participation by Germany and Italy.  In the end, only six vessels were built and none for any foreign buyers. 

The PHMs were envisioned to be minimally manned and include a mothership for maintenance and support.  Manning and crew activities were to be limited to port/starboard watches.  Maintenance, logistics, and support were to be provided by a converted LST acting as the mothership.  We see, then, that the ships were designed to the same operational manning and maintenance concept as the LCS.

It was originally intended to operate the PHMs in the Mediterranean, Baltic, and North Seas with a homeport in Sicily.  In actuality, the PHMs wound up operating exclusively in the Caribbean, largely involved in the war on drug efforts where they were quite successful due to their high speed and maneuverability.

The class was eventually terminated and retired though no reasons were ever offered beyond vague cost issues that were not valid.  The real reason was, undoubtedly, that lacking the sponsorship of the CNO, the “big” Navy simply had no use for small vessels and no desire to attempt to integrate them tactically or operationally into Navy missions.

Pegasus Class Hydrofoil

The PHM packed a large punch for its size and represents the Hughes approach to distributed lethality.  The weakness in this approach is the lack of over the horizon sensing.  The weapon, the Harpoon anti-ship missile, outranges the sensor.  Such a vessel would either be dependent on off-board sensors or need to get much closer to the target, thus negating much of the standoff range of the weapon and increasing the risk to the launching vessel.  In littoral warfare where coastlines might offer concealment and ambush possibilities, the lack of sensor range might be acceptable.  The PHM offers a real world experiment in the Hughes distributed firepower concept.  Unfortunately, the vessels never had the opportunity to operate in their intended environment and this limits the ability to draw conclusions about their potential combat effectiveness.

The PHM was a remarkable vessel and the similarities and parallels between it and the LCS are interesting.  The PHM was intended to use the exact same manning and maintenance model that the LCS is now attempting to use.  The firepower (76mm and 8x Harpoon) of the PHM is, arguably, greater than the LCS and certainly far greater in terms of weapon density.  Further, the indifference of “big Navy” to both their uses is striking.

It is worth noting that the Chinese (and other countries) are developing the Type 022 Houbei class missile boat which is a functional equivalent of the Pegasus PHM.  Would squadrons of PHMs offer a viable counter to Chinese missile boats?  It’s something to think about. 

Here’s a nice summary of the class.


  1. I believe the PHMs also had chaff dispensers to protect against ASMs.

    1. Chaff isn't much protection especially against modern ASM's. When they're in foil mode the radar signature can get a lot larger when the spray is kicked up.

      Best defense against PHM or FAC's? Helicopters with ASM's. British Lynx's had a turkey shoot with their Sea Skua's again Iraq in the '91 war.

    2. Seal Of Lion, just a reminder that the historical data on defense against anti-ship missiles is pretty clear. Defensive success rates for passive defenses (ECM, chaff, flares, etc.) are around 80%. That's pretty good!. Whether chaff, specifically, is effective, I don't know but the overall passive defense is historically quite good. See Hughes for the raw data.

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    1. From my research, that appears to be a myth. The operating cost was a quarter Or less of a Perry which makes their cost insignificant on an absolute basis and quite reasonable relative to their combat power.

      I found no reference to maintenance issues.

      The range is quite short for a carrier. The range is quite good for a littoral ambushed.

    2. "Ambusher" - damn autocorrect

    3. I know nothing about foils.

      Does fuel consumption explode when they are foil borne? Or are does the reduced drag offset it to a large degree?

    4. The cost of operating was almost free in terms of absolute dollars. In a relative sense you could call it expensive for the vessel's size or you could call it cheap for the firepower it carried. The point was that operating costs were not a justification for termination. They cost very little in actual dollars.

    5. Jim, they ran on diesel in hull mode and turbines in foil mode.

    6. Smitty, I think it depends not just on the circumstances under which the vessels shall be used, but also the fact that this specific design, and this specific size may not be optimal, it may not be right sized.

      Traditionally FAC are very much a form of highly mobile ASM batteries, or mine warfare in congested waterways, but nowadays, thanks to miniaturization their potential capabilities, as well as the capabilities of examples of such classes in active service have grown substantially.

      The Hamina-class for instance has ASW capabilities, it should also not be infeasible to equip them with small, potentially armed UAVs and maintain an expeditionairy RHIB. And have a small, cheap, highly survivable platform (due to it's size and speed), with much of the general capabilities of a low-end frigate, without the cost or range.

      But you do not need such enormous range under all circumstances.

    7. They are highly mobile, they also have high procurement, operating and maintenance costs, whereas a small vassal like this can provide a constant presence for much less than it would cost to keep the required number of fighter-planes armed with ASMs and ASW planes on station 24/7.

      Also due to their small size and profile they can be hard to detect, and their speed and agility make hitting them hard. Also the same argument against these such ships, in favour of ASW planes like the S3 Viking, or fighter/bombers can be made quiet often against any other surface vessel, in fact presumably more so as the other vessals are even more expensive relatively speaking.

      At the end of the day, I think the modern long-range, multi-role, UAV equipped FAC is a compliment to a balanced littoral defence force, rather than an alternative to any single system. I still think there is definitely utility in not putting all your eggs in one basket. For instance one might find that their airfields can be monitored, or their use of airspace predicted or in some way denied.

      I really do think it's important to make the distinction between the littoral environment (and the EEZ), what is needed to secure this area, and the open oceans. These sorts of vessals are more suited to the littorals, what you are describing seems to be something that has a much greater operational range (not that greater range isn't advantageous for increasing time on station within the littorals), and operates outside of the domestic air-cover.

      Therefore traditionally doctrine would call for the use of strike carriers, organized into task-forces or battle groups. Personally I am a fan of lighter carriers, akin to the proposed Sea-control ship, that could be loaded up with MPC like the S3-Viking, and a few light tactical planes for self-defense. Japan has been building something very similar to this, but with helicopters. Such a ship would allow large amounts of ocean to be patrolled.'

      But for patrolling the littorals, I see a place for shorter legged vessals, whether it would be one class of LCS or a combination of different types is another issue, but there is definitely a place for a smaller vessal. I think people like zumwalt were realists.

    8. "I'd rather pay to operate one multi-role, globally-deployable frigate than four short-ranged FACs."

      I'm sure you'd agree that it all depends on what you're trying to accomplish.

    9. "At the end of the day, I think the modern long-range, multi-role, UAV equipped FAC is a compliment to a balanced littoral defence force, rather than an alternative to any single system."

      Quite reasonable and well said.

    10. "I'd still prefer the Super Hornets or P-8. They have more high end combat value.

      I agree there is a need to have patrol vessels. I just don't see the value in high-speed, short-ranged FACs."

      Again, it depends on what you want to accomplish.

      Aircraft operating from bases suffer from the fact that the airbase location is exactly known and a peer enemy is not going to allow us to operate our airbases. Ballistic and cruise missiles will negate our airbases fairly quickly. Aircraft operating from carriers will be used for missions other than the type of local, littoral sea control missions that a PHM/FAC would do.

      A PHM/FAC also offers the type of presence/deterrence that I know you're fond of, that an aircraft can't.

      I don't want to turn this into a one-or-the-other debate. Ships and aircraft will have their roles and both will be useful.

    11. "'d still prefer the Super Hornets or P-8. They have more high end combat value."

      I get that. I wonder though if you could have this craft do those missions and save wear and tear on the SH's. You could probably have an ambassador class last a long time doing those kind of low end missions; saving some flight hours on the SH's.

    12. I don't think you can just wave the super power status, and then assert therefore that a well balanced, littoral defence force is unnecessary, then ignore it completely, or attempt to secure it with platforms that are unsuited such as USN cruisers.

      Brute force is never a good soloution, sure the USN might need less such forces than say the PLN but too say it needs no such forces, particularly in an era of agressive forward deployment near potential conflict zones, sometimes in littorals.

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    1. Yes he did. I stated that the Pegasus represents Hughes distributed firepower philosophy, not his ideal vessel.

    2. What's funny is that a 500-1000 ton hydrofoil would probably outgun the LCS. It'd probably be as fast or faster as well, being a hydrofoil at burst speed.

      Funny .. or sad.

      That and the cost would be much cheaper for what you get.

    3. "A suitably-equipped LCS will (eventually) be somewhat competent at both of those missions."

      Wow! Given the total lack of success after a decade of development, you still are buying into the LCS?? Yes, I noticed your use of the phrase "somewhat competent". Still, your degree of faith in the absence of any evidence, whatsoever, is inspiring. I guess that's why they call it faith!

      Go Team LCS!

      Just having some fun with you!

    4. "An LCS is better at LCS missions (maybe, someday)."

      There's a low standard to meet!

    5. We should probably compare the LCS to ships of similar displacement and perhaps role.

      I've noted that perhaps the closest comparison is the Russian Steregushchy-class corvette. It's slower, but it's quite heavily armed.

  4. I love the Pegasus if only because I spent hours with this on my Apple II:

    I think one of them ended up on a river somewhere. I did find this group

    trying to restore one.

    In all honesty, I'm not sure what the useful range the PHM's could target, nor do I know if its 76mm was stabilized or not...

    but it seems like it could give the LCS a hell of a run for its money. If they could only target to 25 miles out the Pegasus could launch Harpoons at an LCS before it could ever fire back. And the LCS couldn't outrun it; especially with LCS 1's range issues.

    I'm not specifically LCS bashing. Just pointing out that for a ship that's supposed to operate in the littorals, it will have to face high speed missile boats carrying ascm's, and from what I can see it doesn't really have an answer. Most nations would trade a couple 200 -400 ton craft for a 3000 ton LCS.

    This is especially true as we are seeing ships like the Fort Worth patrol without significant backup that I can see.

    1. You make good points. And I hope you have some pepto for your valiant effort.

      My concern is that it seems the LCS is starting to take cruises alone, like the Fort Worth. I wonder if its going to start to be treated like a Frigate that has more capability because its what they have to fill that gap.

      The SSC's would have an advantage over missile boats... but I think there's only going to be 20 of those. And, I'm a bit cynical that they'll actually pick a AShM for the SSC and install it.

    2. PHM pegasus on apple ][e was one of the best game / simulation of its time... more on the action and less on the simulation of course..

      shooting down incoming Missile with Oto Melara 76mm cannon is hilarious..

    3. Provided accurate targeting data, Oto Melara claims several subsonic missiles can be engaged and defeated simultaneously with the modern versions of their 76mm cannon.

      It is a very versatile and most excellent cannon, it has the highest volume of fire by weight of projectiles per minute, of any naval gun, and with the modern vulcano submunitions allowing attacks out to ~70KM, it is extremely versatile and well suited to a vessal who's job is to patrol the littorals.

      It is also very light and has a very small profile compared to many other naval guns. And it is much cheaper than it's larger relatives.
      It is therefore an excellent cannon for small crafts.

    4. What was funny in the game was the Pegasus taking hits from AShM's and still floating/moving/fighting.

      Still, it was a blast of a game. IIRC you could control not just the Pegasus but supporting Helo's as well. In some ways it was like Harpoon, the arcade version.

    5. What was funny in the game was the Pegasus taking hits from AShM's and still floating/moving/fighting.

      Still, it was a blast of a game. IIRC you could control not just the Pegasus but supporting Helo's as well. In some ways it was like Harpoon, the arcade version.

    6. "But in any case, the LCS with SUW module wasn't originally intended to fight ASCM-armed FACs. That was still the purview of air power and other systems. It was supposed to handle "swarms" of smaller vessels."

      Quite right and a good point to keep in mind. Of course, one can reasonably argue about what the primary missions should have been but it's only fair to note that the LCS was never intended to be a ship-killer, as you fairly point out.

      Good comment.

    7. "Provided accurate targeting data, Oto Melara claims several subsonic missiles can be engaged and defeated simultaneously with the modern versions of their 76mm cannon."

      Anon, the Mk57 was/is claimed to have the same kind of anti-missile, AAW capability and yet operational experience shows that it is quite limited and, at least on the LCS platform, wildly inaccurate if the ship is making more than 10 kts or so.

      The point is that manufacturer's claims are always wildly exaggerated and the reality is always far less. That doesn't mean that the 76 mm is not a good general purpose gun but until someone proves it can shoot down a cruise missile in a realistic test, it's just an unsubstantiated claim that history suggests can't be met.

    8. That PHM's may/may not have had bigger a role in the US Navy. I think its fair to say that they never really got the shot.

      Could they have performed a roll in the Persian gulf? I don't know.
      It would have been interesting to find out. In the end I think we would have not made more anyway. But it was an interesting class.

      " it's only fair to note that the LCS was never intended to be a ship-killer"

      That's very fair. I disagree with the premise, but its very fair.

      I just wish they'd taken a more PHM approach to the LCS; but done it honestly:

      Lets build 6 and see what we can do with them.

      Then 'The mission module isn't working' or 'The missile we planned on using got cancelled' isn't such a big deal. And the evolving mission for this thing (I have a quote somewhere from an admiral about how the LCS would "Kick the A$$" of anything else in the littorals) would just be the normal experimentation of a worthwhile idea.

    9. "Any ship operating alone is vulnerable to swarm attacks. Even a Burke is susceptible. If enough missiles are shot at it, some will get through"

      True. But in a situation where there isn't a swarm the Burke could hold its own. If anything happened when the Fort Worth ran into that Chinese Frigate, the Fort Worth would have likely been sunken or at least badly mauled.

  5. The concept of a large (relatively) number of small ships would also help the SWO community with retention and personal professional growth, because they should (at least until Millington gets involved) be commanded by junior officers. This would alleviate many of the complaints in the SWO community and fantastically strengthen the Navy Officer Corps. That would more than offset any real operating costs.

  6. What a surprise.....not. Well, it looks like it's a surprise to USN leadership.....

    1. If that ship goes into combat against anything save an extremely lightly armed opponent, it is likely to end very badly.

      Heck, even a terrorist attack, like the Cole attacks would probably be the end.

      Also, if the reports from GAO and DOT&E are to be believed (and my guess is they are), then there's an even bigger problem - the weapons systems are not even working properly.

  7. The FAC is a defensive, sea denial system - operationally, and to some extent tactical, traditionally dependent on support from shore establishment and land based air defence - USN is in the business of global sea control.

    The FAC is not a good FAC-killer - the supported missile armed helicopter is - the USN have no requirement for a FAC.


    For a FAC in hiding - targeting was and is offen done with passive ESM - that's when a enemy radar illuminates the FAC's ESM system the FAC identifies the radar type and offen gets usable position and bearings for a missile attack.

    1. A low cost, low risk, modular patrol vessel - something like the The Royal Danish Navy's Flyvefisken-class - would fit the bill.

    2. That would do it - and it is big enough to share most of the LCS's mission modules.

  8. They used to operate out of Key West doing drug ops.

    Did they ever use these as opposition force for training the US carrier and amphibious groups. They often sent them down to the Caribbean for training but I can’t remember the PHM being involved either as friendly or opposition forces.

    Seems like a missed opportunity. Or didn’t the upper command not want to disrupt their carefully orchestrated training exercise with a half dozen PHM commanded by junior officers who might not mind showing up the big navy.

    1. "Did they ever use these as opposition force for training the US carrier and amphibious groups."

      Not that I'm aware. "Big Navy" seems to have largely ignored the PHMs and marginalized them by sticking them off in a corner to do drug smuggling patrols. The Navy made no real effort to see what they could do. The same may turn out to be true of the LCS. So far, the LCS is not being deployed into operationally relevant areas. To be fair, the LCS has no operationally relevant modules so deployment would be pointless.

    2. They just deployed LCS-3 to South China Sea. That's about as operationally relevant of an area as I can imagine.

    3. PS - I am not an LCS fanboy. I personally think deploying LCS to PACOM is a "net negative" for the Navy.

      But the fact remains that Navy is using it there.

    4. Anon, no, the LCS is not being deployed in an operationally relevant manner to an operationally relevant area. It was built for anti-swarm in the MidEast, MCM, and ASW. There are no operational MCM or ASW modules and an LCS with the extremely minimal ASuW module is not being deployed to the MidEast. PACOM is just a PR tour. Read the report on Freedom's tour. It didn't do anything. It just sat in port and did a few PR appearances when they could get it working.

    5. I am not sure how you are choosing to define "operationally relevant manner" since you did not mention that criteria in your first post. So I will take a crack.

      Fort Worth (LCS-3) was doing the sort of presence mission that FF(x)Gs have done since early 00's. Like it or not - showing the flag and acting as a 'tripwire' are important missions.

      To repeat - I am not a big fan of LCS. But we do need ships over in PACOM for day-to-day, low-end ops. I'd rather send an LCS, and reserve DDGs for high-end operations.

    6. Anon, operationally relevant, in the case of the LCS, means using them for what they were designed for: MCM, and anti-swarm threats in the MidEast as well as ASW aimed at Iranian diesel subs. The LCS is not being deployed to those areas.

      I have no problem with show-the-flag work but we don't need to send a $700B LCS to do that. We can put a US flag on any old ship and send it to visit foreign ports.

  9. How brilliant, I had missed this class and have now spent a happy hour researching and looking at some very cool pictures. Thanks CNO.

    1. You're welcome! I'm here to help and entertain! I always found the PHMs fascinating as the modern day equivalent to the WWII PT boat.

  10. I'm wondering how much a modern 500-1000 ton hydrofoil would probably cost and the weapons that could be put on it.

    It would be pretty fast at burst speeds (being a hydrofoil has this advantage).

    The Russians have a boat called the Matka-class, about ~250-260 tons fully loaded. It's pretty well loaded for it's size:

    - ~42 knots
    - 76mm gun
    - AK-630 missile defense
    - 8x Kh-35 Anti-shipping missiles

    Range probably is not too good (these are in the Caspian Sea I think), but they'd work fine in any littoral and as a defensive sea denial ship.

    The big drawback of hydrofoils is their complexity and sometimes they can be high maintenance.

    They can have issues if they hit something too (garbage, marine life, etc). That being said, I know Hong Kong uses hydrofoils a lot - I'd love to get more information about that.

    1. I should also note that the hydrofoil is not too good for rough seas as well (foils down anyways).

  11. I served aboard USS Aquila (PHM-4) from September 1989 until the squadron was decommissioned. I then transferred to Pre-commission duty aboard USS John S. McCain (DDG-56). I was the EW1(SW) for the Aquila. I was also a Master helmsman for the ship. They were very capable vessels. The costs to operate the squadron command, Mobile logistics Support Group (MLSG) and the six hydrofoil ship was at that time 6% of SURFLANT's annual budget. The ships actually could run on diesel fuel or JP-5 fuel. JP-5 fuel was primarily used to keep the fuel injectors cleaner. During hull ops fuel consumption was 230 gallons per hour for the two diesel engines and the two ships service power units (SSPU). During foil ops we used 1035 gallons per hour. The ships did have RBOC MK-34 mounted on the port and starboard sides on the 01 level.


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