DDH Hayler

Helicopters have long been recognized as one of the most effective anti-submarine (ASW) assets and ASW surface ships have routinely carried one or two helos for that specific purpose.  The problem with ship based helos is that the limited number (1 or, at most, 2) guarantees very limited coverage.  Helos are notorious for maintenance challenges and a ship with, say, two helos can be expected to have perhaps six to eight hours of airborne ASW coverage per day, on average.  One potential solution is to increase the number of helos on a ship thereby creating the aviation (helo) destroyer (DDH).  One such effort was the Spruance DDH 997 derivative, the USS Hayler.
 
Litton, the designer and manufacturer of the Spruance class, proposed a DDH 997 Spruance derivative with a hangar lengthened by 40 ft and widened to the full beam of the ship thereby allowing it to accommodate 4 SH-60B Seahawks.  Curiously, the flight deck remained sized for a single helo and precluded simultaneous flight deck operations by multiple helos.
 
In the event, the DDH version of the Hayler was never built.
 

DDH Hayler Design

Image from www.shipbucket.com,

MhoshiK, Mconrads, Hood, J. Scholtens

 
Destroyer Helo ASW Operations
 
Just as the value of an aircraft carrier is wholly dependent on the abilities of the air wing, so too is the value of a DDH dependent on the abilities of the helos.  With that in mind, let’s take a closer look at small number helo ASW.
 
Four helos might seem an ideal solution to providing helos for ASW as one might assume that a 4-helo ship could maintain one helo in the air continuously.  However, even if that were possible, that’s not really the way helos would be used in ASW operations.  More typically, helos would surge to a suspected contact which, regardless of the outcome, would then result in multiple helos being ‘down’ for some significant period of time and result in gaps in the desired 24 hour coverage.  Of course, this assumes that multiple helos were available to surge.
 
One also needs to recognize that a single helo, assuming one could keep one helo in the air continuously, is only marginally effective at detection.  The helo’s sonobuoys (whether dropped or dipping) are short range and the area/volume of ocean to be covered around a ship or surface group is immense and ever changing due to the movement of the surface ship/group.  Helos are highly effective at prosecuting contacts but much less effective at detecting submarines in a ‘cold’ search effort.  Ideally, one would like to detect possible contacts with surface ships, at long range, and then use helos to prosecute the contact.
 
As we consider the operation of ASW helos, we need to bear in mind what the definition of an ‘available’ helo is.  First, and foremost, it is a helo that can fly;  no easy task given helo maintenance needs!  Second, the helo needs to have the requisite weapons to be effective.  For example, a helo that drops both its torpedoes is, instantly, toothless.  Yes, it can still search and track a contact but it can’t do anything about it.  Two lightweight torpedoes is not a lot when dealing with a submarine.  In other words, in combat, when torpedoes will be dropped at a profligate rate at any marginal contact, four helos with just 8 torpedoes is not going to provide much effective coverage.  Helos will have to spend much of their time shuttling back and forth to a ship to reload torpedoes.
 
Of course, helicopter ASW is a numbers game.  To be ridiculous, if one had forty helos continuously searching the surrounding area/volume, they would likely be fairly effective.  However, that’s unrealistic.  What would be realistic is a squadron of, say, four DDH vessels with, in that case, 16 helos.  In the case of a convoy or task force, there might well be several to dozens of DDH escorts which would, indeed, provide useful numbers of helos, in the aggregate.
 
Recognizing the importance of numbers in the ASW helo game, this leads us to the true ASW helicopter carrier of which there are, have been, many examples.  The main characteristic of the helicopter carrier is, of course, the capacity to carry and operate large numbers of helos.
 
 
 
Other Examples
 
The Japanese developed two 2-ship DDH classes, the Haruna and Shirane, which could carry three SH-60 type helos while retaining conventional destroyer weapons and sensors.  I’m unaware of any other examples by any other countries.  It is interesting to note that the Japanese produced the two mini-classes and then abandoned the DDH for helicopter carriers in the form of the succeeding Hyuga class.  I do not know what the rationale was but it suggests that the DDH was found to be less effective and efficient than a true helicopter carrier.
 
There have been numerous examples of ASW helicopter carriers but that’s not what we’re looking at in this post. 
 
 
Conclusion
 
It seems clear that the DDH concept has limited value due to the limited number of helos unless the ships are grouped in fairly large numbers.  That being the case, one has to wonder whether the cost of fielding several to dozens of DDH’s could be better spent on a true ASW helicopter carrier.  A helicopter carrier with, say, 18-24 helos would be the equivalent of 4-6 DDH’s.  At a very optimistic $1B per DDH, that would equate to $4B-$6B available for a helicopter carrier.  At a more realistic cost of, say, $2B per DDH, that would equate to $8B-$12B which would allow two to several helicopter carriers for the price of the DDH’s, depending on the degree of commercial adaptation incorporated into the carrier design (a large merchant ship with a flat deck would suffice!).
 
It is also clear that the tactical use of ASW helos is not so much searching as fixing and attacking.  This suggests that if one did want to build a DDH, the ship’s ASW sensors would be just as important as the helos, themselves, as they would be counted on to provide the initial detection.  This means that the DDH design should be a highly specialized, intimately integrated ASW design, as opposed to a mere flight deck on a hull as was the case for the LCS.
 
The lack of actual DDH designs in naval history suggests that the navies who considered the concept found it wanting for whatever reasons.  Our analysis suggests this is the case.  A DDH could, under the right circumstances and with a carefully considered CONOPS, be useful.  Unfortunately, carefully considered CONOPS are not a characteristic of the US Navy.
 
The DDH would seem to have some potential but, overall, the resources would be better spent on ASW helicopter carriers.
 
 
 
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[1]Capt. Michael C. Potter, USNR, Electronic Greyhounds, The Spruance-Class Destroyers, Naval Institute Press, 1995, ISBN 1-55750-682-5