Thursday, July 17, 2014

CV 5 Yorktown

Yorktown - first modern US carrier

CV 5       Yorktown

Class:     Yorktown            CV 5       1937, 30 September:      commissioned
                Enterprise           CV 6       1938, 12 May
                Hornet                 CV 8       1941, 20 October

                19,875 tons         standard
                25,500 tons         deep displacement

                809ft 6in / 246.6m            overall
                770ft / 234.6m                  waterline
                802 x 86ft                         flight deck
                244.3 x 26.2m

Beam:   83ft 3in / 25.4m

                21ft 6in / 6.5m                   standard
                26ft / 7.9m                         deep load

Aircraft:                96
Crew:                   1,875 men

Armament          (as completed):
                5in    / 127mm guns x 8
                1.1in / 28mm guns x 16
                0.5in / 12.7mm mg x 24

                2.5 – 4in / 64 – 102mm   vertical belt
                1.5in / 38mm                   deck

                Geared steam turbines
                9 boilers
                4 shafts

                120,000 hp / 89,500 kW
                32.5 knots

Range:  12,000nm / 22,220km @ 15 knots
Fuel:       4,300 tons

Note biplanes on crowded flight deck

The Yorktown, CV 5, was the first in a series of three carriers that included the legendary Enterprise, CV 6, and the Hornet, CV 8, famous for the Doolittle Raid on Tokyo in 1942.  The design of the Yorktown class of carriers was the result of compromise between treaty restrictions and fleet experience with large carriers.  The Washington Naval Treaty of 1922 was an agreement primarily between Britain, Japan and the United States to limit the number of their warships.  Its effect was to hold the size of the Yorktown to 20,000 tons.  Experience with the 36,000 ton Lexington and her sister carrier, the Saratoga, demonstrated the offensive capability of large ships carrying extensive air wings.  By contrast the 14,500 ton Ranger was considered a failure by the Navy because it was inadequately powered, poorly protected and its aerial operations were too easily disrupted by rough seas.

With tanker in Coral Sea

Despite Yorktown’s compromised size it would be the first true modern carrier of the United States and it would provide the basis for the next-generation Essex class carriers that emerged with great impact during the Second World War.  The Lexington class carriers were battle cruiser conversions and lacked the efficiencies that might have come with being designed as a carrier from the keel up.  The Navy could have improved on the Yorktown’s protection had it build the ship closer to 27,000 tons but then treaty limits would have limited carrier production to just it and the Enterprise.  Navy admirals wanted three ships so the Yorktown class carriers were reduced by 7,000 tons, enabling a third Ranger-size carrier to be built – the Wasp.  Unfortunately the Wasp suffered from the same vulnerabilities as did the Ranger and it was sunk by torpedoes within three months of being introduced to the Pacific Theater in 1942.

Struck by torpedo at Coral Sea

Carrier speed is important when operating with the fleet and the Yorktown, like the Lexington that preceded it, was as fast as the heavy cruisers that were its escort.  These ships could top 32 knots when needed.  Launching heavy aircraft from a short deck is not as dangerous as landing on that same pitching deck but it is a challenge having its own peril.  A plane falling into the drink from an unsuccessful launch is almost always fatal – being that it’s in the path of the oncoming carrier.  Carriers divert from the fleet’s course when needed to launch into the wind.  Its speed and oncoming wind combine to maximize the plane’s lift but it also means the carrier must quickly regain lost ground with the fleet after the planes are launched.  Smaller carriers like the Ranger and Wasp weren't large enough to hold the massive power plants necessary to generate fleet carrier speed.

Recovering from dive bomber attack

Both the Lexington and Saratoga came initially with eight inch guns and the armor needed to do battle with an enemy cruiser.  These were America’s first real carriers and it was believed they would have to hold their own in battle with surface ships.  The armor and large guns needed for this role created a substantial weight penalty for the carrier.  At this time the aircraft carrier’s purpose was primarily to provide reconnaissance for the Navy’s large battleships.  The biplanes that populated the carrier’s air wing were too light and underpowered to be anything more than pesky gnats when it came to a clash between twelve inch guns and foot thick armor.  During the 1930s the transition was made to heavy, more powerful monoplanes and it became increasingly evident that the carrier was by itself an offensive force of reckoning.  The carrier’s defense was not measured in guns and armor but in the size of the air wing it carried.  The measure of its power was in getting all your planes into the air in the shortest possible time.

Dealing with bomb damage below deck

Getting quick patch-up at Pearl

By now dive bombing techniques had countered a ship’s ability to rapidly maneuver out of the way of plane-dropped bombs.  Aircraft had become muscular enough to make airborne torpedo attacks lethal for most any naval vessel.  By 1940 a carrier’s air wing was a mix of fighters for defense and the offensive power supplied by dive bombers and torpedo planes.  Just prior to December 7, 1941 the Yorktown’s mix of fighters and bombers was typical for the time.  It consisted of:

                Fighters:              F4F Wildcat –                 19
                Dive Bombers:  SBD Dauntless –             36
                Torpedo plane: TBD Devastator –             18

Normally there were a few additional planes stored on the hanger deck as a reserve.   The torpedo plane could also be used as a horizontal bomber but this approach was rarely effective in naval battle.  Dive bombers were used for scouting duty by replacing bombs with external fuel tanks and fighters could provide escort to the carrier’s bombers. 

Dousing fires at Midway

The installation of radar on the fleet’s carriers in 1940 significantly enhanced the effectiveness of the carrier’s fighter protection.  Approaching aircraft could now be identified from 70 miles out giving the flattop time to beef up its routine combat air patrol circling overhead.  One possible hitch was the displacement of aircraft on the flight deck.  Whereas the British and Japanese policy was to store aircraft on the hanger deck, American naval practice was to have as much of the air wing as possible positioned on the flight deck.  This arrangement saved time in getting all your planes airborne.  The obvious problem occurred when you wanted to launch specific aircraft that happened to be at the rear of the pack.  Placing the fighters at the front made them immediately available for rapid defensive response but it didn't provide space needed for landing when it came time to refuel.  This brings up one of the advantages of having two carriers working in tandem.  One flattop could have its flight deck loaded and ready for offensive action while the second carrier could keep its flight deck cleared of all aircraft but fighters, dedicated to providing the necessary overhead combat patrol.

Destroyer takes torpedo intended for Yorktown 

In practice, the task force surrounding the carrier, whether American or Japanese, was always searching for the opposing carriers.  Discovery of an enemy’s carriers invariably resulted in a quick launch of the task force’s complete air wing.  Whoever struck first was the most likely victor.  The age of the aircraft carrier had arrived.  Knock out an enemy’s carriers and their surface ships must either flee the scene or risk being sent to the bottom of the sea from a swarm of airborne bombs and torpedoes.  The battleship has an offensive reach of no more than twenty miles.  Aircraft from a carrier can strike suddenly out of the blue from their floating base two hundred miles away.  This was dramatically demonstrated at Pearl Harbor and, again, at Midway six months later. 

Bomb punches through wooden flight deck

The Japanese were slow to appreciate the defensive need for radar.  Had their carriers at Midway not relied exclusively on air patrols they might have been able to counter the devastating blow inflicted on them by the squadrons of SBD Dauntless that pounced unexpectedly from nearly straight overhead.  Like their American counterparts, the flight decks of Japanese carriers were not armored.  Effective armor would have made them top heavy and would have required them to make unacceptable cuts in the number of aircraft they carried.  This vulnerability made dive bombing possibly the greatest risk to a carrier’s survival.  One well-place bomb could leave the flight deck unavailable for further aircraft operations.  Fighters were the best means of carrier defense.  By the time of the Battle of the East Solomons, in August, 1942, both the Enterprise and the Saratoga had doubled their fighter complement to 36 F4F Wildcats.  The Yorktown might have done likewise had it not been sunk at Midway – sent to the bottom by a submarine’s two torpedoes, having first been slowed from three bombs in a dive bombing attack. 

Destroyer pulls survivors from water

It took an extraordinary effort on the part of repair crews at Pearl Harbor for the Yorktown to even make it to Midway.  The vessel managed to survive three bomb hits and two torpedoes to her port side at the Battle of the Coral Sea just the previous month.  At Pearl the Yorktown was given a quick 48 hour patch job and sent back to sea along with her sister ships, the Enterprise and HornetYorktown’s squadron of SBD Dauntless would be responsible for sinking the Japanese carrier Soryu while dive bombers from the Enterprise would destroy both the carriers Kaga and Akagi.  A last gasp attack from the carrier Hiryu led to the Yorktown’s demise.  Hiryu, the fourth and final Japanese carrier, was itself dispatched the following day.  The entire battle had been waged without either fleet sighting the other except from the air.

Yorktown capsizes and sinks

The design of the Yorktown, CV 5, displays the confidence the US Navy had developed for the offensive role the aircraft carrier brought to the fleet.  This respect was first earned in fleet exercises by the Lexington and Saratoga during the twenties and early thirties.  The Navy’s faith in a carrier-based task force would be vindicated in battle during the first difficult months of the Second World War by Yorktown and her sister ships, Enterprise and Hornet.  They would each achieve a distinguished place in history.

Yorktown in its early days

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