We have reports from NavalToday and Maritime-Executive that the Libyan Coast Guard, using a 30mm auto-cannon, opened fire on and sank a Russian owned, Comoros-flagged oil products tanker, the GOEAST, believed to have been smuggling Libyan oil.

It is not the first time the Libyan Coast Guard has used deadly force, and apparently not the first time the GOEAST’s parent company has been accused of smuggling.

I found this particularly interesting because it seemed to contradict my long held belief that the Coast Guard is unlikely to be able to forcibly stop, much less sink, a medium to large merchant ship in a timely manner with gun fire if it were employed in a terrorist attack. There are many questions about the sinking for which I have not seen answers. What might this incident say about our own ability to stop a terrorist attack using a merchant ship?

The GOEAST was a small and elderly tanker. Admittedly a terrorist organization is more likely to have control of a ship like this, than a larger and more modern vessel. It displaced 9700 tons and was built forty years ago in 1977. It would have been considered relatively large in WWII, but not now. We don’t know its state of maintenance, but it was probably poor. We don’t know how it was loaded, incomplete or asymmetrical loading, and the resulting free surface effect may have contributed to its loss. We don’t know how long it took to sink or how long it could steer and make way. Even after being damaged, could it have completed a terrorist mission before sinking?

The actions of the Libyan Coast Guard were probably an excessive use of force. We have no information about what happened to the crew of the amount of pollution that resulted. Whatever the justification for the attack on the GOEAST, it is good to see a degree of success in using a relatively small gun to stop a sink a ship, but there are reasons why we may not be able to take much comfort in this example.

The Libyan Coast Guard vessel appears to have been a former Italian Bigliani II  class patrol boat equipped with a twin Oto Melara-Mauser 30mm gun.

The Bigliani IIs are not big ships. They are 84.7 tons full load and 27 meters (88.6 feet) in length, 6.95 m (22.8 feet) of beam, with a draft of 1.26 m (4.13 feet). That is actually  slightly smaller than our 91 ton full load 87 foot Marine Protector class WPBs. This illustrates that even our small patrol boats could carry much heavier weapons.

The 30mm gun, visible in the video has a relatively high rate of fire, but that is largely irrelevant for our purposes (unless we are being shot at) since even our 180 round per minute chain guns can exhaust their ammunition in only a few minutes.

The 30mm gun fires common NATO rounds which include the armor piercing fin stabilized discarding sabot (APFSDS-T) round that A-10 Warhogs use against tanks. Compared to our 25mm gun’s corresponding APDS-T round, the 30mm has a higher muzzle velocity and weighs 71.6% more. This long rod tungsten penetrator is more likely to be able to disable a ship than even our 57mm rounds, which may penetrate the hull but will likely explode before reaching the engine.

The tanker was not returning fire, which could have kept the patrol boat at a distance, and radially reduced the accuracy of fire.

I still have doubts about the ability of a gun to reliably stop a medium to large merchant ship with a determined crew. There are other alternatives, but an upgrade to a 30mm gun on our patrol boats and larger vessels would certainly increase our chances of success.