ASW and Helicopters

Most people seem to take it as an article of faith that every ship that conducts anti-submarine warfare (ASW) must have a helo or two; that it’s impossible to conduct effective ASW without a helo.  This is absurd.  ComNavOps, on the other hand, has proposed an austere, small, cheap, expendable corvette-ish ASW vessel without a helo.

Can ASW be effectively conducted by a surface vessel without a helo?  Let’s analyze the concept and see.

A good place to start any analysis is by looking at history.  History has much to teach us if we’re willing to learn.

In WWII, ASW was conducted by a variety of platforms ranging from small corvettes to destroyer escorts to destroyers to full fledged hunter-killer ASW groups centered around small aircraft carriers.  Even sailing ships and small commercial vessels took part in the ASW effort!  These efforts were supplemented by carrier and land based aircraft of all sizes and types.

Interestingly, none of these ships had helos!

The backbone of the WWII ASW effort in the Atlantic was the corvette.  The British Flower class corvette was a good example of the type with 267 (numerically, almost equal to the entire US Navy fleet today!) being built during the war.  These small ships were not individually supremely capable at ASW but they were effective due to their numbers and presence.  A submarine will go far out of its way to avoid detection.  With enough corvettes around, a submarine can be forced away from potential targets or suppressed enough to allow the potential target to safely pass the submarine by – a mission kill on the submarine.  Even if the corvettes never detected the enemy sub, their very presence was often enough to “defeat” the sub.

Another lesson from WWII and the Cold War against Soviet submarines is that ASW is not conducted in isolation, one ship against one sub.  ASW is a team effort.  Just because a ship does not have a helo attached does not mean that it cannot call on aircraft when a submarine is detected. 

Having acknowledged some historical lessons about ASW, let’s now turn to the fundamental question, what are the characteristics that make helos effective in ASW?  The answer is speed and standoff.

Speed – The speed of a helo, relative to the speed of both the submarine and the helo’s host vessel, is much greater than either and that confers an enormous tactical advantage to the helo.  The helo can reposition faster than the sub.  The helo can dart from location to location while finding and fixing the sub’s location while the sub is limited to ponderous, slow movements by comparison.  The same speed advantage applies to the helo’s host vessel which can only move at the same speed as the sub and cannot readily gain a positional advantage.

Standoff – The helo’s relative immunity to counterattack by the sub, coupled with the helo’s range, allows the host vessel to remain out of effective range of the sub.  Thus, the prosecuting ASW ship gains a standoff advantage over the sub.  The ship can attack via its helo while remaining at a safe standoff distance.

That suggests that helos should be included on every ship.  Is that really the case?  No, it’s not.

The problem with equipping every ship with helos is the cost.  A helo requires around 70 ft of added flight deck length, 70 ft or so of hangar, fuel storage, munitions storage, maintenance spaces, parts and tool storage, berthing for the twenty or thirty additional pilots and maintainers, larger galley space to support the aviation crew, larger food storage, more fresh water generation and storage, and on and on. 

A thousand foot flight deck to operate fixed wing strike fighters is a highly effective system.  It’s not even debatable and yet we don’t put those on every ship.  Why not?  Cost.  So, why would we think we have to put helos on every ship?

As we noted, helos add enormous costs to a ship.  If you take the helo component away from the LCS, for example, what you have left is a Cyclone class PC which cost $15M-$20M when they were built.  Okay, that’s not an exact match but it’s not that far off.  The point is that the financial impact of a helo is immense and unaffordable.

That’s all well and good but if we don’t put helos on every ship, won’t our ships be sunk as fast as submarines can reload their torpedoes?  I mean, after all, enemy subs will be lined up waiting for our ships to run the submarine gauntlet – I’m guessing one sub in every square mile of ocean, if submarine alarmists are to be believed.  Our ships will have no hope, whatsoever.

Of course, that’s absurd.  For the foreseeable future, China or Russia would be hard pressed to keep ten or twenty subs at sea at any given moment in a war.  China, for example, has around 60 attack subs of which a dozen or so are SSNs and the remainder are SSKs of varying age and capability.  So, the submarine population density in the ocean is almost non-existent.  Of course, submarines don’t just randomly distribute themselves throughout the ocean.  They congregate at known convoy paths, chokepoints, and transit locations.  That has the effect of increasing the apparent submarine density, somewhat.  That still, however, results in a remarkably submarine-free ocean.

Consider the WWII U-Boat experience.  Contrary to popular impression, despite Germany’s large submarine force (almost 1200 U-boats built from 1935-45), submarine encounters were not all that common.

In all, during the Atlantic Campaign only 10% of transatlantic convoys that sailed were attacked, and of those attacked only 10% on average of the ships were lost. Overall, more than 99% of all ships sailing to and from the British Isles during World War II did so successfully. (1)

So, despite an incredible fleet of 1200 U-boats, vectored to well known convoy routes, submarine attacks were relatively uncommon.  China, with a fleet of 60 odd submarines, will simply not have enough subs to mount more than occasional nuisance attacks.

Submarine alarmists also proclaim that the US carrier fleet will all be torpedoed and sunk within an hour of the start of a war.  Is this really the case?  Are warships that susceptible to submarines?  No, they’re not.  Not even a little bit.

As always, let’s turn to history for some data.  How many warships did the US Navy lose to submarines?  The answer is very, very few.  The US Navy had a fleet of 6000 ships and lost around 21warships to enemy submarine attacks.(2)  In addition, a handful of small patrol boats were also lost.  Of those 21, one was a small carrier (Wasp), two were escort carriers, one was a heavy cruiser, one was a light cruiser, and the rest were destroyers and destroyer escorts. That’s it.  That’s the entire loss to enemy submarines.  Of course, there were a few additional sub attacks that resulted in damage but not sinking.  As a point of reference, Japan built around 200 submarines for WWII.

Those 21 or so warship losses represent a loss rate of 0.3% of the total fleet.  That’s an utterly insignificant loss rate.  That’s approaching zero losses!

So, why was the warship loss rate so small in the face of a thousand U-boats and a couple hundred Japanese subs?

The answer is that because warships don’t travel repetitively across the same predictable paths, as convoys do, submarines can’t congregate against them.  Encounters tend to be random or the result of a warship being operationally ‘anchored’ to a location such as the Wasp which was ‘tied’ to the Guadalcanal operating area which allowed enemy subs to congregate.  The fact is that warships, by the unpredictable nature of their operations, are very hard to find.

In addition to being hard to find, warships travel much faster than convoys.  A WWII convoy would travel at around 12 kts or so.  Warships tend to travel around 18-20+ kts.  This makes achieving an intercept solution very difficult for a submarine even if the sub detects a warship.  If the sub speeds up to achieve an intercept it becomes louder and more detectable.  Unless a warship has the bad luck to, literally, stumble across an enemy submarine, the risk from subs is very low.

There are some who will claim that modern subs are quieter, faster, and have better sensors so ships will be helpless before them.  Well, this would be true if ships hadn’t progressed at all since WWII.  However, they have.  Modern ships have helos, better sensors, better fire control, networked data sharing, better sonobuoys, bi/multi-static sonobuoys, etc.  Thus, the performance gains by submarines since WWII are offset by the gains by surface ships.

Nothing has changed today in the submarine/anti-submarine battle.  Subs still have a hard time finding warships in the open ocean.  Subs still have to maneuver to achieve weapon launch positions.  Submarines still make more noise when they speed up. 

None of this should be construed as implying that the submarine threat can be dismissed.  The threat is real and deadly.  However, a logical analysis demonstrates that the threat is nowhere near as common or automatic as submarine alarmists would have us believe.  The combination of substantially fewer enemy subs than were operating in WWII and the inherent surface ship advantages of unpredictability and speed guarantee that the threat is not particularly prevalent.  Thus, and this is the key point, not every ship needs helos!

Inevitably, some readers will interpret this to mean that ComNavOps is against helos on any ship.  Well, that’s absurd.  Aside from the fact that I haven’t stated that, it would just plain be foolish.  We need ASW helos – just not on every ship.

What ship(s) should have ASW helos?  I’ve discussed this in previous posts but, to briefly recap, we need helo-equipped hunter-killer ASW carriers and true helo-equipped destroyers, not the cruiser/battleship Burkes that are tied to high value AAW escort duty and are too expensive to risk in ASW.

The lesser destroyer escorts and ASW corvettes (see the blog Fleet Structure page), without helos, fill the role of presence and suppression, as discussed above in the example of the WWII corvettes.

So, what have we learned from the preceding discussion?

• The submarine threat, while serious, is vastly overblown as regards frequency of encounters.
• The main submarine threat is to convoys which follow repetitive, predictable routes.
• Due to their speed and unpredictability, warships are unlikely to encounter submarines.
• Effective ASW is as much about suppression as detection and attack.
• Based on cost and the unlikely chance of submarine encounters, not all ships need ASW helos and there is no justification for such.

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(1)Wikipedia, “Battle of the Atlantic”, retrieved 22-Nov-2019,

https://en.wikipedia.org/wiki/Battle_of_the_Atlantic#Outcomes

(2)Wikipedia, “List of United States Navy Losses in WWII”, retrieved 22-Nov-2019,

https://en.wikipedia.org/wiki/List_of_United_States_Navy_losses_in_World_War_II