Fleet versus Escort Carriers

Hi All,

During World War II, a fleet carrier had a capacity of approximately 90 aircraft compared to that of an escort carrier with a capacity of approximately 30 aircraft.

For each fleet carrier produced, it seems that the same fighting power could have been achieved with the construction of three escort carriers. Consequently, prior to battle, three escort carriers would have sailed forth for each fleet carrier.

What were the tradeoffs (advantages and disadvantages) of each of these concepts? Please don't just include tactical advantages/disadvantages during battle but include all factors such as cost, time to construct, intimidation factor, manpower requirements, etc.

Thanks in advance,

Bob Guercio

 

One consideration that strikes me right away is speed. Escort carriers would not need to be fast, since they would only have to keep up with merchant ships. A look at Wikipedia confirms this, with most being capable of less than 20 knots.

By contrast, fleet carriers could be capable of 30 knots (32 for the Essex class). This would be a great advantage tactically, since a fast fleet carrier could choose whether or not to engage slower escort carriers. Also, it would assist in takeoff operations.

 

However, in the scenario of using escort carriers in all battle conditions, they would have been designed to be fast!

I guess this takes us into the realm of "what was" and "what could have been".

I think we should consider what could have been because you should decide which way to go before you go there and, once decided, you design accordingly.

Bob Guercio

 

A few quick ones (no doubt others will add more and better argumented things)

1. The speed (already mentioned) but apart from the tactical and strategic disadvantage you also get the fact that escort carriers need more wind to create enough over deck wind for flight operations so are more dependent on the wheater .

2. Protection, barely protection in the escorts.

3. Size = ability to absorb damage

4. No heavy AA (only symbollically one or two guns), especially important when the VT fuse came in use.

5. the only escort carriers that could handle the Hellcat were the Commencement Bay's, but then you are already talking about 18.000 ton ships, so you get only two for an Essex. (so 54 aircraft with all the disadvantages listed)

Escort carriers were very useful in a number of roles and did play the role of fleet carriers a few times when the latter were in short supply.
They could be mass produced on smaller slipways than the fleets. And freed fleet carriers for the front line (but they also ended up in the front line sometimes) And they were an irreplacable part of the fleet that won the atlantic and pacific war.
But they were surely not a replacement and in actual task force not even an addtional asset due to the lack of speed.

Many Greeetings

Aglooka

 

Norman Freidman in his US warship Design History series, Aircraft Carrier Volume, discusses both the history and rationale for building both escort carriers and fleet carriers. There had been a debate within Navy circles since the inception of aircraft carriers, over whether it was better, considering the limited resources (money mostly), to build a few very large and powerful "flight decks" or to build many smaller, but less capable, "flight decks". There were good theoretical arguments on both sides, but basically, the trade-offs involved cost and time versus efficiency and offensive/defensive power. The US Navy consensus had always favored large heavily armed carriers (usually designated "fleet" carriers) with large airgroups, because ton for ton, these ships were demonstrably more efficient and cost-effective than smaller, cheaper "light" or escort carriers.

However, with the rapid approach of war, it became imperiative to produce as many carrier flight decks as possible in the shortest time possible. Franklin Roosevelt, who often injected himself into technical debates on the relative merits of naval ships, favored the more austere and cheaper ships because these were easier to build quickly, and ship for ship, were cheaper. The USN argued that they might be cheaper, but weren't really that much quicker to build (one Essex clas carrier was launched just 14 months after it's keel was laid) and weren't cost-efficient. They also pointed out that escort carriers, because they were smaller and slower, couldn't operate certain newer aircraft and were easier to sink because passive defensive measures like anti-torpedo bulkheads and extensive compartmentation could not be incorporated in their designs. It was really a form of the old classic question, "how many eggs should you put in one basket"?

Escort carriers however could be converted from merchant ship hulls which did speed their entry into service and, if they were not used in areas of intensive combat, their lack of armament, aircraft operating capabilities, and passive defensive measures wouldn't really matter that much. To give satisfactory service, fleet carriers had to be built from scratch. Although it wasn't always possible to guarantee that escort carriers wouldn't accidently be exposed to heavy attack by enemy forces, it was generally the case that they were not used in the front lines without being protected by regular fleet units. Escort carriers were invaluable for duties such as aircraft ferrying, invasion air support, pilot training, etc. which otherwise would have required the services of fleet carriers, and would have wasted most of the fleet carrier's capabilities.

To make the trade-offs really work to advantage though, one needs enough carriers to fulfill both the separate and different roles of the fleet carriers and the escort carriers. Japan built both Fleet carriers and escort carriers for the same reasons the US did, but the IJN did not find the trade-offs very useful because it didn't have enough of either type and ended up trying to use escort carrer equivalents in the roles of fleet carriers and vice versa. They found out that neither type gave satisfactory service in both roles and ended up being wasteful of resources. Being able to design, build, and properly utilize both fleet and escort carriers does save time and resources, but it is a strategy that only wealthy countries can use.

 

Yes, but what price in tonnage would that cost ?

greetings

Aglooka

 

Exactly.

Building fast (25+ knots) escort carriers would have negated most of the inherent advantages of escort carriers. It would make them more expensive, larger, and would increase building time appreciably. In addition, one of the attractions of escort carriers for the US was that they used standard merchant ship propulsion plants which were far easier to build, maintain, and operate, thus reducing costs drastically.

Essentially, a "fast" escort carrier would be what the US Navy termed a "CVL" or Light Fleet Carrier. The USN converted only nine of them from cruiser hulls in 1943, as basically a stop-gap measure for the temporary lack of CV's. They weren't considered as useful in combat as Fleet carriers, or as cheap and easy to build as escort carriers, but they did have the advantage of quickly increasing the number of flight decks which could be used in front line combat.

 

The question becomes more interesting in my view if we balance the building of fleet carriers against the light fleets as the Brits did. Any opinions on that ?

Aglooka

 

I thought that a fleet carrier was designed to carry out offensive tasks, and the escort carrier is a defensive tool.

I'm a landlubber so never mind if it seems stupid.

 

Well let's look at it like this:

Cost of a CVE vs the cost of one Japanese 550 lb bomb or a torpedo. Because that's about all the IJN had to hit it with to make a CVE disappear. All that steel invested, and a number of trained personnel go with it. That's why CVE's were always kept to the rear (Samar notwithstanding), they couldn't take ANY punishment, really.

Way too slow for any operations that might involve an enemy fleet. They'd just get run down and stomped.

 

Not always.
USS Santee survived torpedo hit from Japanese sub, although it was not deadly 610 mm. Long Lance, but 533 mm. torpedo.
http://en.wikipedia.org/wiki/USS_Santee_(CVE-29)

Regards.

 

No. As mentioned before, some aircraft needed the full size (faster) CV to operate.
Another consideration is that subs have difficulty targeting the fast CV's, but can more easily pace and hit slower CVE's.

So it isn't a good idea to build CVE's instead of CV's, but it is a good idea to use smaller yards that CAN'T build CV's to convert mechant ships to CVE's

 

That one really is the exception. And the Santee was very lucky.

 

Merchant derivation CVE are not likely to be effective in a carrier battle or other high intensity scenario, they have just too many limitations (speed and ability to absorb damage) , a different story is the "light" carrier, a ship built from the keel to military requirements but smaller than the "heavy" carriers.

IMO the best comparaison is Zuikaku (29.500t 75 planes) vs two Zuhio (14.000t 30 planes), no story there on which I would choose,
The British "light" carriers are more difficult. they were built to civilian navy standards, so probaby not very good at surving damage, but a comparison to Essex (30.000t 100 planes) or two Majestics (13.000t 52 planes) seems to show no marked advantage for the "big" ship.
BTW I picked Essex for comparaison as the armoured deck Illustrious CV have a different design philosophy.

 

I have a feeling that the little "Jeep" carriers are getting sort of short shrift here, since they were never supposed to do the job of "Fleet Carriers" but to supplement them at less expense. Here is a pretty decent "history" of the concept and the carriers themselves.

Goto:

U.S. Navy - A Brief Carrier History: The Escort Carriers

 

The escort carriers were quite adequate for ASW work or proving air support to invasion forces after the opposing airpower had been beat down or to ferry planes forward as others have mentioned. I'm not sure that they could launch a fully loaded torpedo bomber though. US CVE's did operate Avengers but I don't think they even carried torpedoes in their magazines. The constraint on naval construction in WWII was for the US largely one of slips and slip sizes. Thus CVEs, CVLs, and CVs all made sense and complimented each other to a fair extent.

 

Maybe it's just me, but I see a difference between an 8" AP, which usually went through the CVE's at Samar, and an aerial bomb or torpedo that usually explodes on contact (but didn't pass though the ship without exploding). True, the cruisers inflicted heavy damage on the CVE's, but not the extent a torpedo or bomb would.

The other part of my point is that the slow CVE's would be easy prey to faster ships of the line, or aerial attack. That the IJN didn't press home their attack at Samar was more because of bad orders and lack of direction by Kurita, then anything Taffy 3 actually did. If Kurita had not ordered a general attack (equivelent of a cavalry charge), and his advance on Taffy 3 had been more carefully planned, not to mention if his men had correctly ID'd Taffy 3 for what it really was, the Taffy's might have all gone down.

 

Of Six US CVE's lost during WWII, two were lost to torpedoes, three to bomb/kamikaze hits and one to gunfire.
Liscome Bay, CVE-56, Japanese torpedo
Block Island, CVE-21, German torpedo
Gambier Bay, CVE-73, gunfire
St-Lo, CVE-63, bomb/kamikaze
Ommaney Bay, CVE-79, bomb/kamikaze
Bismarck Sea, CVE-95, bomb/kamikaze

I'm fairly sure a number survived bomb hits, need to confirm that only one survived a torpedo hit (which seems likely).

 

I think we are neglecting the impact of the CVE's in the battle of the Atlantic escorting convoys and as hunter/killers against German U-boats.As to being far easier to sink than fleet or light carriers, that may be true, but remember the only US CVL lost during the war was also to a single aircraft.