Frigate Helge Ingstad Design - Damage Survivability


Absolutely correct. Except that I believe the navy requirements for damage stability and survivability have been incorporated in the current rules. ABS Rules for Naval Vessels were written in collaboration between USN and ABS so that USN could capitalize on ABS proficiency in maintaining the rules. In general, they trace back to original Bureau of Ships (BuShips) design data sheets. BuShips was established by Congress on 20 June 1940, by a law which consolidated the functions of the Bureau of Construction and Repair (BuC&R) and the Bureau of Engineering (BuEng). The Bureau of Construction and Repair (BuC&R) was the part of the United States Navy which from 1862 to 1940 was responsible for supervising the design, construction, conversion, procurement, maintenance, and repair of ships and other craft for the Navy. So, one would have to go way, way back in time to find a period in history when warships were designed only by first principles.


Hm! ABS and similar classification societies Rules are only about hull strength scantlings/dimensions and machinery capabilities of merchant ships to be insured against loss. ABS, DNV, BV, GL, etc have no rules about hull subdivision and damage stability of any ships. Why should they? It is the IMO and its SOLAS rules that explain that. Cargo ships (and war ships!!!) are 0 compartment ships and sink like stones in incidents. Various passenger ships are 1 or 2 compartments ships and sinks less frequently. War ships are not considered at all. They are not insured. Sailors on them are not passengers. They are idiots and soldiers. If they are attacked and sunk, nobody really cares except the enemy.


All hull compartments below main deck/water line on all ships are supposed to be watertight, i.e the bulkheads up to the man deck shall have no openings and the manned compartments shall have two escapes. If you are in one compartment and want to go to the adjacent compartment, you have to go up to the main deck via one escape and down into the other compartment. But seamen and sailors are lazy. They want doors in those bulkheads, so they do not have to climb up and down. And plenty authorities agree. That’s why such ships are not seaworthy, ever…


Yes, except for the navy ship which is on bottom of the sea, and the merchant ship which is getting a new paint job.


The obvious difference between a naval craft and a commercial craft is that a naval craft is designed and built to go into harm’s way. The Naval Administration determines, on a case basis, the levels of threat from enemy aggressions (weapons and weapons effects) that the vessel will face, the manner in which the vessel will avoid them (e.g., by signature reduction), and the level of survivability against those threats. However, naval craft also encounter hazards at sea during their normal operations, due to the environment, accidents or the inherent risks involved in training for war, and must be able to survive them. Therefore, the requirements for Classification under class rules distinguish between “inherent” survivability requirements against fire, collisions, flooding and the operation of own-ship weapons (e.g., gun blast), and requirements imposed by the Naval Administration on survivability and signature reduction against enemy threats. These distinctions are as follows:
Mandatory for Class:
• Flooding and damaged stability
• Fire protection
• Damage control
• Protection against own-vessel weapons effects
• Structural redundancy and residual hull girder strength
• Propulsion system redundancy
• Electrical system redundancy

Guidance for supplemental requirements determined by Naval Administration:
• Protection against chemical, biological and radiation
• Protection against underwater threats, e.g., shock and whipping
• Protection against above-water threats, e.g., blast, fragmentation, electromagnetic pulse
• Signature reduction


US Navy’s stability requirements (DDS 079-1) can be found online:

Chapter 2.5.3 discusses damaged ship stability and defines the longitudinal, transverse and vertical extent of damage that the ship must be able to survive without foundering. In case of combatants, the longitudinal extent of the damage is 15% of length between perpendiculars. I would expect this to translate to two adjacent compartments in way of machinery spaces and three compartments elsewhere unless they have managed to make the engine rooms short enough. While this applies to US Navy vessels, I would expect a NATO country such as Norway to adhere to similar rules for general compatibility.


Well, whatever you call it is just a stupid joke. I doubt HI were built according to that nonsense.


Hm, are naval vessels built to more stringent damage stability criteria than commercial ships? Please give an example.


Are you asking if a 15% * L criteria is more stringent than a two-compartment standard? The answer is yes.


A simple proof of this is a) - a two-compartment standard is considered a relaxation of the baseline standard (12.5% or 15% LBP).

edit: Note that SOLAS 2009 requires probabilistic stability analysis for civilian ships which is difficult to compare to traditional 1/2/3-compartment approach. However, it should be noted that the old SOLAS damage extent was 3…11 metres in longitudinal, B/5 in transverse and unlimited in vertical direction. Compared to this, DDS 079-1 is best described as “B/5 bulkhead won’t save you this time”.


Anyway, the real risks of naval ships are to be hit by torpedoes, blown up by sea mines, bombed by enemy planes, gunned by enemy ships, etc, and it seems HI were designed with little protection against those. I wonder if HI had a double bottom and how it could have protected against a sea mine? Or maybe it was single bottom?


I’m on an extremely restricted internet connection at the moment, but maybe someone else can root out and post some video footage of old destroyers and frigates being used for target practice? If reason doesn’t do the trick, maybe the pretty visuals will drive the point home.


Not commenting on any navy in particular, but I think that it has been so long since they have been in a proper war they have lost sight of survivability. Look at the HL, Fitzgerald, Mcain etc. They have virtually the equipment of a cruiser packed into a sardine can. They depend on defensive systems, stealth, CIWS, missiles, etc like a fly weight boxer depends on speed and agility, but one hit and they are out.

Look at the Washington treaty ships of the 30’s, still constrained but far more survivability.


It’s always a race between developing weapon systems and means to either defend against them or survive their effects. Modern torpedoes and, to some degree, sea mines are designed to explode under the keel and “break the back” of the vessel, and you can’t really build a strong enough hull girder to withstand such blast. However, I have the feeling that modern (western) anti-ship missiles with relatively small warheads are designed primarily to disable the target (by destroying antennas, radars and deck-mounted weapon systems), not to outright destroy and sink it. In a way this is a more economical approach: it’s better to stop two enemy ships from carrying out their missions with lighter munitions compared to completely destroying one with a twice heavier shot. There’s also a humane aspect - there’s no need to kill a thousand sailors if you can just make them go back home. A smaller and faster missile, preferably launched as a swarm, is also more difficult to detect and intercept. Of course, in the meanwhile, the eastern bloc is developing heavier systems with the Chinese already deploying ballistic anti-ship missiles designed primarily to hit American aircraft carriers.

Anyway, in the meanwhile, modern ships are rarely armored against anything but small arms and shrapnel. Instead, they rely on active protection - close-in weapon systems, jammers etc. Having to carry less armor (=weight) also makes modern ships smaller, faster and more agile without requiring excessive power.

edit: …as @Tellarian already pointed out in his message above mine. However, are you comparing modern destroyers and cruisers to ships of similar size and function from the pre-war era and not the capital ships?


It looks like the collision damaged the HI superstructure side above main deck in way of the aft generator room, aft engine room, stabilizer room and forward engine room below. The damaged HI hull side below the main deck only affected the cabin/store room, aft generator room and aft engine room. Only the watertight bulkheads of the aft generator room were damaged. So maybe the aft generator room was first up-flooded above the double bottom causing total Black Out and loss of electrical power minutes after the collision. And then the ship was lost. Not even the bilge pumps (to pump out water) could be started.Interesting case. Imagine a warship totally lost when the generators fail! The aft peak, the stabilizers room and the forward engine room were not affected at all by the collision but were apparently subject to progressive flooding trough openings in the bulkheads.

Tanker Sola and Norwegian navy frigate Helga Ingstad collide off Norway

I’d say it’s possible that the transverse bulkhead between the aft machinery room and stabilizer room was also damaged considering the high-energy impact at the bulkhead deck level. However, the leak may have been relatively small (say, a ruptured welding seam), but coupled with the faulty stuffing boxes it may have accelerated the progressive flooding.

Assuming HI was built to similar standards as US Navy ships, I’d say it would have survived the three-compartment damage without progressive flooding to undamaged spaces.


Modern warships have to a greater degree become multi purpose vessels. The admirals want to show politicians they are getting more bang for the buck. The one shot/one hit to disable weaponry works fine against lightly built vessels. Exocet missiles did more harm from the unburnt fuel than the warhead. Thats was the reason that many were not so successful against merchant ships in the tanker war - the Iraqis launched at extreme range for fear of the Iranian Tomcats.



That reminds me of the Dutch tug Pool Zee which was hit by an Exocet missile in the Persian Gulf in September 1985. The missile entered the bridge deck on the starboard side, shot under the CE’s bed and exited on the port side without exploding. However, a fire broke out which destroyed the bridge and the crew had to leave the ship. She was towed to Bahrein but was declared total loss and arrived at the ship brokers at Gadani Beach in January 1986.


You are right. Only close up inspection of that bulkhead after removal/salvage of the wreck will provide the answer. I wonder why the Norwegian authorities will not already, today provide photos/films/videos by divers already taken. This is just a stupid accident of great interest! Why the secrecy? Norwegian, national security? What do you think?


This is from the initial report:

To start with, flooding occurred in three watertight compartments on board ‘KNM Helge Ingstad’: the aft generator room, the orlob deck’s crew quarters and the stores room. There was some uncertainty as to whether the steering engine room, the aft most compartment, was also filling up with water. Based on this damage, the crew, supported by the vessel’s stability documents, assessed the vessel as having ‘poor stability’ status, but that it could be kept afloat. If more compartments were flooded, the status would be assessed as ‘vessel lost’ on account of further loss of stability.

Next, the crew found that water from the aft generator room was running into the gear room
via the hollow propeller shafts and that the gear room was filling up fast. From the gear room,
the water then ran into and was flooding the aft and fore engine rooms via the stuffing boxes in the bulkheads. This meant that the flooding became substantially more extensive than
indicated by the original damage. Based on the flooding of the gear room, it was decided to
prepare for evacuation.