Tuesday, June 20, 2017

Fitzgerald Collision

You’ve all read about the recent collision between the 505 ft long, 9000 t, Burke class destroyer, the USS Fitzgerald, and the 730 ft long, 40,000 dwt, Philippine-flagged container ship ACX Crystal.  I’ve had no comment, thus far, because there has been insufficient factual information to comment about.  There was no information on the circumstances of the collision, the exact extent of damage, or even the specific damage control measures beyond general statements about some flooding. 

Now, however, some snippets of information are becoming available.

“USS Fitzgerald suffered damage on her starboard side above and below the waterline. The collision resulted in some flooding.” (1)

“…
Fitzgerald is under her own power, although her propulsion is limited.” (1)

Navy Times reported , “that Auxiliary Machine Room 1 and two crew berthings were completely flooded.” (1)

“A top Navy admiral acknowledged Sunday that the destroyer Fitzgerald was in danger of sinking …” (2)

“… Fitzgerald suffered an enormous gash in its hull under the waterline, causing both berthing compartments and the auxiliary machine room to flood rapidly …” (2)


However, one of the pieces of information that I’ve been waiting for has become available and I’ll offer an analysis.  That information is pictures of the damage to the ACX Crystal.

Look at the Fitzgerald and note the degree of visible damage.  From the comments and visible damage, it is clear that the ship was very badly damaged and was in danger of sinking.







Now, look at the ACX Crystal.  The only visible damage is the bent bulwarks above the deck line and a possible small tear in the ship’s plating at the bow.







How do you reconcile the extremes of the visible damage?  That the larger ACX Crystal would inflict more damage on the smaller ship is to be expected but that the Crystal would show almost no hull plating damage at the point of impact speaks volumes about the relative thickness and strength of the two ships construction, framing, and hull plating.  The Fitzgerald’s hull plating crumbled like tissue paper while the Crystal’s was barely dented other than the thin bulwarks above the main deck.  In other words, the container ship was, apparently, built like you’d expect a warship to be built and the warship was built …  well …  weakly.

Let’s be fair and acknowledge that we have no description of the Crystal’s damage other than what can be seen in the photos.  It could be that the ship suffered serious damage and flooding below the waterline but there is absolutely no indication that that is the case.

The Navy needs to seriously rethink its warship design philosophy and construction practices and standards.  From a construction perspective, this is embarrassing and ominous.  What will happen when missiles and torpedoes start impacting our ships in combat?  All historical evidence suggests that our ships will prove to be extremely fragile.



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(1)USNI News website, “7 Sailors Missing, CO Injured After Destroyer USS Fitzgerald Collided with Philippine Merchant Ship”, Sam LaGrone, 16-Jun-2017,

(2)Navy Times website, “Fitzgerald Crew’s ‘Heroic Efforts’ Saved Their Ship From Sinking, Admiral Says”, David B. Larter, 18-Jun-2017,


30 comments:

  1. I'm no expert, but I expect the different areas of impact on each ship account for much of the difference, in addition to the obvious discrepancy in mass.

    USS Fitzgerald certainly came off better from her collision with a larger vessel than USS Frank E. Evans did from her collision with HMAS Melbourne: https://en.wikipedia.org/wiki/Melbourne%E2%80%93Evans_collision

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  2. No expert either, looks to me like the cargo ship came "down" which might explain the "crumbling" effect to DDG? Would seem that DDG structure would crumble like the front end of a modern car to absorb the hit.

    I do hope lessons are learned from this, I'm sure somebody with a lot more math skills than me can deduce how much energy was used to create this much damage and compare it to a what a ASM would do for starters.....

    Condolences to the families.

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  3. To be honest, I see nothing to illustrate a weakness in the Burke's armor scheme. I would imagine the bow to be the strongest part of the ship. That explains the lack of damage to the crystal. Likewise, something had to give in the collision, and it happened to be the fitzgerald.

    My concern is this the second incident to this region this year. Maybe it's time to review our procedures.

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  4. Its also a case of 4x the mass being and all the forward momentum of the M/V being focused on a small, sharp area on the TOP of the the destroyer. Note less damage lower down. An online calculator shows that a 40,000 ton (metric) at 12 mph is 42,000,000 foot-pounds of energy which is far greater than any warhead most ASM missile warheads could generate. Had the point of impact been lower the ship would probably have sunk.

    Rather than the Burke's weakness it shows how much stronger a steel ship meant to keep 40,000 dwt is by sheer necessity.
    When some have argued for things like an arsenal ship built on a merchant hull this is what they were thinking of, not the LCS which might as well be balsa wood.
    I seem to recall back during the "tanker war" when the Iranians were mining the gulf that a a big commercial ship or two hit mines but were able to make port with much less repairs than anyone would expect and no damage to their cargo.

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  5. I suspect you might find that the point of impact on ACX Crystal is a bulbous bow - not visible in the phots - below the surface. Would also explain why there was substantial underwater (hence flooding) damage to Fitzgerald.

    Bulbous bow plating on ACX Crystal probably of the order of 1" thickness, vs DDG hull plating in the deckhouse of around 1/4", maybe 3/8" at a push.

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    1. Additional - the bulbous bow would have hit the below water strake of plate on the DDG which is probably 5/8" to 3/4".

      The bit that impacted the deckhouse would probably have been a stem casting (fairly solid given the straight stem above the bulb), plus 1/2" to 5/8" plating in way of the flare around the foc'sle.

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    2. "Additional - the bulbous bow would have hit the below water strake of plate on the DDG which is probably 5/8" to 3/4"."

      I have a cross sectional construction drawing of a Burke IIA and it shows the side hull is composed of strakes of either 15.3# (3/8") or 17.85# (7/16") plating.

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  6. Still very early but there while it's possible this is just two ships with lax crews acting like cowboys there is also some strange signs. Marinetraffic.com indicates that the tanker pulled off the equivalent of a hit and run. Of course the data could be at fault but needs to be verified if it is inaccurate. Secondly the chain of custody vessel is quite murky. THe vessel is Japanese owned but through a series of holding companies seems to have been chartered to a company in the Philiippines who crews the vessel.

    Rumors are that their running lights and transponder were off. There are also no reports of the freighter crew condition. It is possible that maybe they were carrying something ilicit. Extreme theories are that it may be linked to North Korea. It could just be something as simple as the ship may be in danger of repossession. The global freighter market is over leveraged.

    Either way publicly available data indicates that were extremely odd speed and course changes from the freighter. If it is not excluded then something very strange happened beyond a simple collision. I tend to discount the North Korea theory since if the Navy were covertly tracking illicit cargo then a collision would be avoided by both sides, and why would the captain be in his quarters. \

    Maybe the freighter crew freaked out and thought no one would notice, did not report things until an hour later and now refuse to say anything so they don't get in trouble with whoever really runs the ship.

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    1. For some reason the incident was reported an hour after it happened- which means the strange course data came after the collision not before
      "Investigators were expected to want to interview the Crystal’s crew to ask, among other things, why there was nearly an hour’s delay in reporting the crash. The Crystal reported the collision at 2:25 a.m. on Saturday, but Nippon Yusen determined that it occurred around 1:30 a.m." NY Times

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    2. The so called strange course is easily explained. Crystal hit the ship, stopped, turned around to render assistance,and then when that was done, turned back around to continue on course.

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    3. "The so called strange course is easily explained. "

      Except that I've read no report that they rendered any assistance and, in fact, some reports have described the collision as a "hit and run".

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  7. If Port Royal was totaled after riding the shoals, and the resulting Radar mis-alignment, I expect this ship to be totaled also. This one might actually be bent down below. But the Cole was fixed so maybe not.

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  8. I suspect the container ship had it screws in full reverse and just bumped the Fitzgerald at a slow speed. If it were cruising at 24 knots it would have cut her in half. I still can't believe it t-boned her smack in the middle. You'd think the Fitzgerald would at least be making a turn away.

    I read the Cole was totaled. It cost more to rebuild her than a new ship, but pride was at stake. Maybe we should call them "tin cans".

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  9. As pointed out by others the Crystal is larger, the bow is a strong part of any ship, and it has that bulbous bow which acts as a ram in this case


    As to the strength of the Fitzgerald, it’s a destroyer and its built to destroyer specification. Now it’s a $ billion plus destroyer and weighs almost 9,000 tons but its build not that much different then a WW2 destroyer or even a WW1 destroyer

    It has no armor, it has some Kevlar, but that is mostly to give some electronics splinter protection

    Its underwater layout is not much different from a WW1 destroyer which has vertical solid bulkheads separating each of the major underwater spaces. So those berthing were separated from Auz 1 by a vertical bulkhead which has no doors in it below the waterline. Aux 1 is separated from Main 1 by a similar bulkhead. The same for the rest of the spaces. Unfortunately the ship hit below the waterline near that bulkhead between Aux 1 and the berthing and so all three spaces flooded since the bulkhead was damaged

    If you were to go to either Aux 1 or those berthing and put you hand on the side of the ship there would only be around half inch of steel between you and the ocean. The bottom of the ship is similar though it does have some fuel or water tanks welded in, but there are spots you can put your hand where there is just a half inch or less of steel between you and the ocean.

    So with the Burkes and even more so with the DDG 1000 they have put a $ billion dollar plus of equipment into a noversized destroyer hull.

    Its not a cruiser hull, even though it weighs as much as a WW2 cruiser and even some pre ww1 battleships, not only is it missing the armor, but its missing the double hull that a cruiser would have. Cruisers and above have a outer hull which starts above the waterline, goes all the way down the side of the ship, turns and becomes a double bottom and then goes up the other side of the hull to above the waterline.

    It won’t stop a modern torpedo but it can stop major damage from collisions, or near misses by bombs and torpedoes or even stop major damage if some speedboat fires a .50 cal machine gun at the waterline. A Burke or a DDG 1000 would have major flooding if someone did that since a half inch of steel or less is not going to keep the bullets out and there are major pieces of equipment on the other side of that steel.

    So lets stop building cruiser sized and cruiser costing ships with destroyer hulls.

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    1. Yes , its surprising they dont have double hulls. This story about changes for Flight IIIA shows a hull section being lowered to confirm the very light structure below
      https://news.usni.org/2015/11/12/navy-industry-working-through-ddg-51-flight-iii-detail-design-draft-rfp-for-ship-construction-released
      Fitzgerald was one of the very early builds but wouldnt have changed much under the water line.
      What is surprising is the reports from the USN that the ship 'nearly sunk' Warships like this are supposed to have much higher stability margins even when they have compartments filled with water. Maybe the watertight bulkheads werent up to the required standards and flooding spread through various apertures. Could be a worry for the whole class, but we need to wait till more information about below water line breaches of the hull

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    2. Reply to Ztev

      That is a good picture showing the light construction of these destroyers

      The piece that being held by the crane shows that the bottom of that space has fuel or water or waste tanks welded in, but the sides just have a single layer of steel between the ocean and the inside of the ship

      That large assembled piece on the ground shows one of the major bulkheads (painted mostly green) that separate sections of the ship. The big hole on the right in the bulkhead is for the starboard shaft coming from the Main 1 engine room which is forward and back to the propeller. The shaft is not that big but there is a watertight seal where it goes through the bulkhead.

      If however you are rammed where one of those watertight bulkheads are you can flood spaces on both sides since the bulkhead would be ruptured

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    3. I'm pretty sure our cruisers stopped having cruiser hulls in the 60s with the Long Beach. Ticonderoga-class cruisers were built on top of Spruance-class hulls starting in the 70s.

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    4. I think what will surprise most people is how large of a hole that container ship caused. It won't be obvious until it's in dry dock. A similar situation happened to the Arthur W Radford (DDG-968) in 1999 when it collided with a 30,000 ton RoRo. The hole was forward of the 5 inch mount, so the damage wasn't as extensive as the Fitz, but check out the size of the hole: http://www.shipstructure.org/radford.shtml
      That was 67 million and 8 months to get back to sea. The Fitz will be much worse off.

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    5. Scott, the link you provided with detailed damage to the Radford showed the post damage analysis meant the ship still was within stability limits
      "The ship maintained sufficient transverse stability following damage (as indicated by the righting arm curve and a GM of 3.16'). Subsequent evaluation of the righting arm curve indicated that the stability met underway wind heel and roll criteria of DDS079-1"
      To me this means they would have had no concerns about sinking. But that maybe hindsight of course.

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  10. If you make the DDG's more heavily armored, you will increase their weight while decreasing their range and speed. The slower and shorter legged DDG's could get so slow that they would no longer be capable of escorting fast CVN's.

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    1. Oh come on, now. Surely you're familiar with the WWII destroyers and cruisers. They had twice the thickness of plating plus additional armor and still were capable of 30+ kts and 5500-10,000 miles range! Check out the specs on WWII ships. We've forgotten what a warship can be capable of!

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    2. Build a large tin can....it is still a tin can...

      Did we philosophically forget building these cheap cold war disposable assets for the 'big one' tm that we carried it over building what are major capital assets?

      Is a Burke more a Fletcher DD in construction method vice a Cleveland or Baltimore cruiser - or hell the Long Beach?

      We lost something somewhere.

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  11. It appears that Navy has had concerns re the hull of the ABs for years and taken the opportunity with the Flight IIIs to change it.

    From memory the Navy has specified thicker hull plating and scantlings from mid hull to stern plus widening the stern above the waterline to avoid water over flight deck, one helicopter was washed overboard and crew drowned, Navy issued a pdf with specs., but it seems to have been pulled as unable to find it now.

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  12. It's very interesting the Burkes don't have a thicker hull for sure I'm starting to think though this accidental collision may not have been so accidental after all no proof yet mind you but just imagine the coupe for a terrorist organization to say hey look at us we sunk a US warship especially as some reports are suggesting it was making a U turn prior to the collision really weird

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  13. I am not an expert on marine warship construction but the berthing area was well below the waterline the pictures depicted above only show part of the merchant ship 4 times the displacement of Fitzgerald. What doesn't show under the bow of the merchantman is the huge bulbous construction (look up a dwg) that inflicted the most damage well below what is visible. Consider that. I'll wait and hear about what happened.

    It's clear there is fault and that will lie with both ships probably... however one can reliably predict that the US warship watchstanders will fry and the Skipper will be relieved..
    b2

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    1. Here's a pic showing the solid bulbous centerline hull that is almost directly south of the bow tip. Imagine that punching into berthing below waterline...:

      http://www.abc.net.au/news/2017-06-18/acx-crystal-after-collision-with-uss-fitzgerald/8628994

      It is a wonder they were able to compartmentalize, equalize and most escape in time at o'dark thirty . Depending on the speed of the cap-T collision and the loaded weight of the merchant ship this was almost worse than a direct torpedo hit!

      b2

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  14. I'm sceptical of this idea that modern warships should be built like battleships, but to be fair one thing we commonly hear -- and which certainly appears to be the case -- is that the cost of a modern warship isn't so much associated with the steel that makes up the hull, but rather all the delicate systems inside and the crew that operate them. If that is the case, then the marginal costs of opting for heavier construction standards would seem worth it even if they only marginally improve survivability against anticipated threats. More than the cost of steel, the greater factor against such standards is probably increased operating cost and reduced endurance due to increased displacement requiring more power and fuel burn.

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    1. "the greater factor against such standards is probably increased operating cost and reduced endurance due to increased displacement requiring more power and fuel burn."

      I'm starting to get irritated at this constant incorrect and ridiculous refrain from so many commenters - sorry it had to be your comment that finally triggered this rant. Do any of you study WWII warship designs? We had ships with twice the weight of armor and plating and yet twice the endurance! How do you explain that??????!!!! And all while maintaining 30+ kts capability.

      Go back and do some research, everyone.

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    2. "I'm sceptical of this idea that modern warships should be built like battleships"

      Who said that? No modern ship should be armored like a battleship unless it IS a battleship. All ships, however, should have the degree of armor commensurate with their size and purpose.

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    3. The closest WW2 ship to an AB Flt 1 at 8184tons loaded is the Juneau class light cruiser at 8450 tons loaded.
      Juneau is 165m and AB1 is 154 m, so shorter but AB1 beam is 20 m and draft is 9.3m compared to Juneau with 16m and 6.25m
      Clearly the longer but thinner Juneau would require less HP to get to 33 kt and it had 79,000shp while AB1 has top speed 'exceeding 30 kts' and has 105,000shp.
      if you wanted a 100,000shp ship you would have the Fargo class cruiser which was 14500tons full load and 185m length and similar beam to AB1 at 20.2m but draft is still only 6.7m.

      The biggest changes have come going away from lots of weight low down such as heavy turbines and boilers to modern light weight gas turbines and modern electronics putting weight high up. As well the power available means top speed isnt achieved by making a very long thin hull.
      The greater max draft now may be because the underwater hull is shallower towards the propellors but would need a full comparison of the below waterline form

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