Lightweight Torpedoes for the Philippine Navy - a Re-introduction to ASW Weapons Systems

Earlier we discussed the possibility of having the MBDA FASGW(H), also known as the Sea Venom or the ANL, for the Philippine Navy (PN). This is due to entry of anti-submarine warfare helicopters being contested between the AW-159 Wildcat and the AS565MB Panther. Both helicopters are capable of carrying the FASGW(H), and both helicopters are the top contenders for the PN's ASW Helicopter acquisition project.

With the impending acquisition, it is worth noting that aside from helicopter launched anti-ship missiles, the PN is also looking at helicopter launched lightweight anti-submarine torpedoes, as specified in the ASW helicopter acquisition specifications. With no decision from the DND and PN on the helicopter platform yet, MaxDefense will be discussing the possible torpedoes models being offered to the PN.

The Eurotorp MU90/IMPACT torpedo, as carried by a French Navy NH90NFH naval helicopter.
Photo taken from aerobuzz.fr website.

Lightweight Anti-Submarine Torpedoes

The DND and PN's Technical Specifications for the ASW Helicopters indicated the following conditions for the anti-submarine torpedo requirements:

- 6 warshot and exercise torpedoes per helicopter (total of 12 torpedoes);

- lightweight;

- impact detonated;

- with sub-surface target homing capability in active, passive, or mixed acoustic modes;

- with a range not less than 10 kilometers;

- seawater battery operated with electrically rechargeable power source;

- to include Flight in Air Material (FIAM) gears;

- torpedoes should be the same as those being procured for the PN's new frigate (pending PN's updated technical specifications for the frigate's torpedo system).

The specifications did not indicate the torpedo's calibre, although it is expected that the PN will be acquiring those in the 323.7mm (commonly known as the 324mm) NATO standard LWT calibre. 

Based on the size alone, the possible candidates for the PN's requirement may include the following torpedo models:

1. Raytheon Mark 54 MAKO (USA);
2. BAE Systems Sting Ray Mod 1 (UK);

3. Eurotorp MU90/IMPACT (France/Italy);

4. LIG Next1 K745 Blue Shark (South Korea)

The US Mark 46 and the Italian A244/S Mod. 3 are probably not being considered, as they are already being replaced by the newer Mark 54 MAKO and the MU90/IMPACT, respectively.

Torpedo Propulsion System:

But each of these torpedo models have different propulsion systems, although majority uses the seawater battery type, which are believed to have less heat signatures and left no wake as compared to thermal propulsion systems like those using liquid propellants. Seawater battery means that it can be activated by exposing them to seawater. So far, only the Eurotorp MU90/IMPACT, the LIG Nex1 K745 Blue Shark and the BAE Systems Sting Ray are powered by seawater batteries. Both the MU90/IMPACT and the K745 Blue Shark are powered by Aluminum-Silver Oxide (AlAgO) seawater battery, while the Sting Ray Mod1 with the Magnesium/Silver-Chloride (MgAgCl) seawater battery from SAFT. The Mark 54 MAKO uses the Otto II liquid fuel, effectively taking it out of the possible choices.

The Mark 54 torpedo being launched from a USN destroyer. Being powered by liquid Otto Fuel II, it does not meet the specifications provided by the PN, which specifically mentioned the use of seawater battery system found in other torpedo models like the Sting Ray, MU90 and Blue Shark.
Photo taken from Wikimedia.

The Possible Candidates:

According to most defense journals, the MU90/IMPACT is the most modern, and probably the best lightweight torpedo in the market today, with its capabilities in terms of speed and range, depth requirement for launching being applicable to shallow waters, high immunity to countermeasures, having an insensitive warhead, broadband sonar and a tactical computer. But this also means that it could be the most expensive of the possible offers. It also suffered some problems with the Australian Navy, which could be a possible reason for doubt by other countries including the Philippines. The MU90/IMPACT is currently in use by France, Italy, and many other nations including Germany and Denmark, and can be carried by the AS565MB Panther, the NH90NFH, and the AW101 Merlin. It can also be carried by the AW-159 and the MH-60/S-70 helicopter, which can be modified to do so and were tested with such configuration a few years ago.

The Eurotorp MU90/IMPACT in both the ship-launched and aircraft-launched variants.

The LIG Nex1 K745 Blue Shark was said to have been developed closely using the MU90/IMPACT as a basis. It uses the same technology for the propulsion and power source, but may cost far less that its European counterpart. It was reported that the torpedo only had a success hit rate of 50% during tests by the Republic of Korea Navy (ROKN) and confirmed by the Defense Acquisition Program Administration (DAPA) in 2012. It is expected that the ROKN will equip its upcoming AW-159 Wildcat naval helicopters with the K745 Blue Shark, in anticipation of their current policy of nationalizing its weapons system as much as possible.

Scale models of the LIG Nex1 C-Star anti-ship missile (above) and the K745 Blue Shark lightweight torpedo.

The BAE Systems Sting Ray, currently in its Mod.1 version, is the foremost lightweight torpedo used by the Royal Navy. Compared to the older Mod.0, it uses a new sonar system, an insensitive munition warhead, a new tactical and navigation system and a new seawater battery system. It also prides itself of being a low maintenance torpedo using longer life seals and improved bearing lubricating system. The Sting Ray Mod.1 is the initial torpedo model carried by the AW-159 Wildcat, and can also be carried by the NH90NFH, and is currently in service with British Royal Navy and Royal Air Force, and the Norwegian Navy.  

A Royal Navy AW-159 Wildcat carrying a pair of Sting Ray torpedoes.

All torpedoes mentioned above can be carried and launched by helicopters, are impact detonated, with sub-surface homing capability in both active and passive modes. All mentioned torpedo models have ranges exceeding the 10 kilometers, 

Ship-Launched Lightweight Torpedoes:

With a requirement from the PN for the helicopter-launched torpedoes to be of the same model as the frigate-launched ones, the selection of torpedoes for both platforms will be dependent on which project will be awarded first. 

The PN also has a requirement for lightweight torpedoes to arm its upcoming new frigates, as well as a possibility to upgrade its existing naval assets to fire torpedoes as well.
Photo taken from Wikimedia.

So far the PN's frigate acquisition project is already going for the second stage bid, but since the PN already decided to separate the acquisition of weapons systems from the frigate itself, there might be some changes in their requirement that can still be made. Although based on commonality and practicality, the original requirement for the frigate and helicopter to have a common torpedo model is still probably the way to go.

Conclusion:

Whatever the outcome is of the acquisition plans for anti-submarine lightweight torpedoes, the main point is that the Philippine Navy will finally be having torpedoes in its arsenal again after a long absence. And not only will it have ship-launched torpedoes, but also air-launched as well. This will definitely boost the PN's capabilities as compared to what it has now, and with proper training, maintenance, and funding, as well as close coordination with its neighbors and allies, the PN may well again be returning to regain its lost prestige as one of the most proficient ASW combat force in the Pacific region. 

MaxDefense anticipates that the acquisition of torpedoes will be separated from the acquisition of the helicopters, as what was done with the PN's new frigate project.

Aside from the Philippine Navy, it is also expected that the Philippine Air Force will benefit from such acquisition plans, with their Long Range Patrol Aircraft (aka Maritime Patrol Aircraft) also expected to be armed with air-launched torpedoes as ASW missions are part of its requirement. 

A C-295 maritime patrol aircraft dropping an air-launched anti-submarine lightweight torpedo during tests. Aside from the PN, the PAF is also expected to acquire lightweight torpedoes for its upcoming Long Range Patrol Aircraft.