ASW Helicopter Procurement for the Philippine Navy

An AW159 in flight. Photo courtesy of Cpl Kellie Williams, RLC/MOD thru Wikipedia Commons

The Department of National Defense (DND) recently announced the allocation of P5.4 Billion (USD 120 million using the Exchange Rate of USD 1 = P 45) for 2 brand-new Anti Submarine Warfare (ASW) Helicopters for the Philippine Navy (PhN), and they expect the acquisition process for these helicopters to be completed within the year.^[1] The news item says that the 2 ASW Helicopters will be assigned to the Del Pilar-class ships, but I am not sure about the accuracy of this as we do have 2 brand-new Frigates which will be needing helicopter support also, hence it makes more sense to assign these units to those Frigates. It is possible that if the helicopters arrive first, they will initially be assigned to the Del Pilar-class ships, but will eventually be moved to the new Frigates once those arrive.

The budget of USD 60 million per helicopter came as a bit of a surprise for me mainly because first, I found it a bit high. At that budget, each helicopter will be almost twice the price of the FA-50 Fighting Eagle Advanced Jet Trainer (AJT) we are getting which is valued at only USD 35 million each.^[2] Second, it seems that while we are getting top-of-the-line ASW Helicopters, there doesn't seem to be any effort to get any sonar equipment for the Del Pilar-class ships, while the sonar requirement for the 2 new Frigates are only generally/loosely defined or not very specific.^[3]

Because of this, I get the impression that the PhN plans to use these ASW Helicopters as the MAIN ASW tool for either the Del Pilar-class ships or the 2 new Frigates. I could be wrong, of course, but right now this is the impression I am getting, and if that is really the case, then I have some doubts about it.

'ASW 101'
First off, ASW Operation is a pretty complex affair, hence let me just share this fantastic reference I found on the web about it. I think the people who wrote it should've spun it off to a book, I definitely would've bought one. It can be used as reference for the terms used in this blog.
- ASW Tactics 101 Part 1
- ASW Tactics 101 Part 2
- ASW Tactics 101 Part 3

'ASW Helicopter Operation'
Helicopters are very useful in ASW operations because they can be used in a number of ways. First is that they can scout ahead of a ship to look for submarine contacts using equipment such Dipping Sonar (sonar equipment that is lowered from the helicopter into the water via cable) and/or Sonobuoys (disposable, remote sonar equipment dropped into the water).

But the main way an ASW Helicopter is normally used is to CONFIRM suspected submarine contacts. For example, if a sonar-equipped ship detects POSSIBLE submarine contacts around the ship and is able to get its approximate BEARING (direction relative to the ship) and estimated RANGE from the ship, then it can direct the ASW Helicopter to that suspected location. The ASW Helicopter can then confirm the presence of a submarine by using the variety of equipment at its disposal to “triangulate” the location of the sub.

This can be done using a number of ways, like if a Dipping Sonar is used then the sonar is dipped in multiple locations around the suspected submarine area and activating its active sonar. The idea is to get a bearing and range reading from each dip, and then calculating their intersections to determine the submarine's exact location. Using Sonobuoys will be easier and faster as their will be no need to make multiple passes or dips as each Sonobuoy is already at different locations, but Sonobuoy use are expensive as they are disposable and each one costs at least USD 250.^[4]

Alternatively, the helicopter can also use a Magnetic Anomaly Detector (MAD) (detects the variation in the Earth's magnetic field due to the presence of a submarine's hull) to confirm a submarine's location by making a series of parallel and then perpendicular passes to determine a submarine's location.

'ASW Helicopter Attack'
Once the ASW Helicopter has the exact location of the enemy sub, if given the permission then it can go and attack it with a Lightweight Torpedo it normally carries. Helicopters are ideal platforms to launch weapons against submarines because they can travel quickly to a location, much faster than a torpedo can. The ASW Helicopter can then drop the torpedo literally almost on top of the submarine, giving it less time to detect and react to the threat and thus increasing the chances of a kill.

Torpedoes when launched from surface ships or submarines are S-L-O-W to arrive to their target, making interceptions of moving targets more complicated. For example, a torpedo traveling at 45 knots or 52 kph will take almost 6 minutes to travel 5 km, upon which time a moving target would've gone a certain distance already hence the need to account for that also. This is why it is more ideal to have helicopter drop a torpedo nearer to an enemy sub (either that, or use Rocket-Assisted Torpedoes).

'ASW Helicopter Limitations'
However, helicopters do have limitations of their own. First is that they have limited endurance of only up to a couple of hours before they need to refuel or even change to a “fresh” crew if needed. Second, all aircraft like helicopters have “consumable” flight hours, hence every time you use them you are eating away at those flight hours, and the faster you use them the faster you will reach the required next maintenance overhaul period.

A Kongsberg ST2400 Variable Depth Sonar (VDS). Photo courtesy of Wikipedia Commons

Also, the more a helicopter is used, the more it wears out which could lead to maintenance problems causing downtime as the aircraft is being repaired. Lastly, helicopters can also be lost due to combat attrition (i.e., shot down). Most ships also only carry 1 helicopter at a time, hence if the helicopter is lost due to some reason and the ships rely on it as its main ASW asset, then the ship will be vulnerable to a submarine attack.

'Ship-Based Sonar Equipment'
Because of this, ASW Helicopters need work in conjunction with ships to ensure that there will be no “gaps” in ASW coverage that a submarine could exploit. In fact, ship-based ASW equipment should be considered as the MAIN tool for ASW, with ASW Helicopters as SECONDARY tool for ASW to COMPLEMENT the ship's ASW equipment. Ships also can carry better sonar equipment because they are less limited in terms of space, weight or power requirements than a helicopter, hence ship-based sonar equipment can be bigger, heavier and more powerful and thus are generally better than helicopter-based sonar equipment.

Actually for me, it is better to have a ship with advanced sonar equipment paired with a smaller ASW Helicopter rather than have a ship with mediocre or no sonar equipment paired with a large, advanced ASW Helicopter. The former is not ideal because it means less ASW capability overall for the ship-helicopter combination.

One of the best sonar equipment available for ships right now are what's called a “Variable Depth Sonar” (VDS), basically a towed sonar equipment which can vary its depth also. Towed sonar means that the sensor is located away from the noise of the ship's engines and propellers, making it more effective at detecting submarines. Another advantage of a VDS is that it can be lowered to the Thermocline Layer where submarines usually hide as it can reflect some of the active sonar signals activated from above the layer. An example of a VDS system is the CAPTAS-4^[5] used on the newest FREMM Frigates by France and Italy.

VDS are usually used in conjunction with Bow or Hull Sonars as the VDS do provide some speed and maneuvering limitations when being used, and also time has to be spent when reeling them in or out. Hence in times when you need to travel faster and/or do a lot of maneuvering, you would want to still have some sonar capability with your Bow/Hull sonars to detect submarines and/or (worst) their torpedoes.

'Torpedo Decoys'
Lastly, despite all of these equipment, my opinion is that current ASW technology tilts slightly in favor of the submarine as shown in the Falklands War on BOTH sides of the opposing forces, hence if the Philippines plans to have a really serious naval deterrent against China, then it has to acquire submarines. I plan to blog more about this later, but in the for now this means that PhN should also invest in TORPEDO DECOYS as it is likely that no matter how good your ASW technology is, advanced Submarines with a well-trained, experienced and determined crews will likely be able to get at least a Torpedo shot off, hence the importance of decoy systems against Torpedoes.

Among these systems would be the AN/SLQ-25 “Nixie”^[6] which is a towed decoy that mimics a ship and is designed to draw torpedoes to it. Even though I think current ASW technology favors the submarine, it still pays to have a strong ASW capability to discourage more attacks from submarines. A weak ASW capability only encourages more submarine attacks, increasing the chances of a submarine severely damaging or even sinking the ship.

'Parting Shot'
These 2 ASW Helicopters were supposed to be paired up with the planned purchase of 2 Maestrale Frigates a couple of years ago,^[7] and the ship-helicopter fit THEN would've been excellent because despite its age, the Maestrale Frigates are great ASW ships. It could carry 2 helicopters for redundancy, had a Prairie-Masker system that made it harder for submarines to detect it, and it had a VDS system.^[8] However, the purchase of the Maestrales were cancelled, but the acquisition of its ASW Helicopters continued.

Getting these expensive ASW Helicopters is actually still very good news, but I think the PhN should also acquire advanced sonar and decoy equipment for its ships to ensure a “proper fit” or “proper pairing” between ship and the advanced helicopters, and right now there are no publicized plans yet to acquire any such equipment.

The PhN has expressed preference for the AW-159 Wildcat for the ASW procurement,^[1] and it seems to be a good choice as it is going to be the main ASW Helicopter for the Royal Navy,^[9] although how it fares with other ASW Helicopters right now in the market remains to be seen. Note that we are getting a lot of helicopters from Agusta-Westland (AW), 5 AW109s for the PhN and another 8 AW109s for the Philippine Air Force, and so far the PhN has been very satisfied with the service provided by AW^[10] hence probably the preference for another AW product which is the AW159.

An AN/SLQ-25 Nixie Torpedo Decoy being reeled in. Photo courtesy of Wikipedia Commons

SOURCES:

[1] DND earmarks P5.4B for anti-submarine choppers, 

http://www.interaksyon.com/article/82880/dnd-earmarks-p5-4b-for-anti-submarine-choppers

[2] PAF going back to supersonic age with South Korean jets, 

http://globalnation.inquirer.net/99297/paf-going-back-to-supersonic-age-with-south-korean-jets

[3] Philippine Navy New Frigate Acquisition Timeline, 

http://rhk111smilitaryandarmspage.wordpress.com/2014/03/06/philippine-navy-new-frigate-acquisition-timeline/

[4] NAVAIR Sonobuoy Team Innovation Earns DoD Recognition, 

http://www.navy.mil/submit/display.asp?story_id=8246

[5]CAPTAS-4 Variable Depth Sonar, 

https://www.thalesgroup.com/en/content/captas-4-variable-depth-sonar

[6] AN/SLQ-25 Nixie, 

https://en.wikipedia.org/wiki/AN/SLQ-25_Nixie

[7] Philippine Navy To Buy Two ASW Helicopter, 

http://malaysiaflyingherald.wordpress.com/2012/11/20/philippine-navy-to-buy-two-asw-helicopter/

[8] Maestrale-class frigate, 

https://en.wikipedia.org/wiki/Maestrale-class_frigate

[9] AW-159 Wildcat, 

http://www.agustawestland.com/product/aw159-0

[10] Navy pleased with support of AW-109 suppliers, 

http://ptvnews.ph/bottom-news-life2/11-11-nation-submenu/27325-navy-pleased-with-support-of-aw-109-suppliers