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.
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| 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
