H.I.J.M.S. Hiryo

Ships in class (1)
  • Hiryo

  • Dimensions:
  • Disp: 106,233 fully loaded
  • LOA: 1200' - 6"
  • Beam: 121' - 7"

  • Performance:
  • SHP: 180,000
  • Boilers: 12 Kanpon
  • Turbines: 4 shaft Kanpon turbines
  • Oil: 23,100 tons
  • Top Speed Trials: 30 knots

  • Armor:
  • Sides: N/A
  • Deck:
  • N/A

  • Main: 32 - 5" in twin mounts
  • Light AAW: 150 - 25mm in triple mounts
  • Torpedo: -

  • Aircraft:
  • Total: 210
  • VF: 84
  • VB: 66
  • VT: 60
  • Scout: 0

  • Ordnance storage:
  • 135 – Type 91 Aerial torpedoes
  • 180 – 800kg bombs
  • 180 – 500kg bombs
  • 936 – 250kg bombs
  • 1056 – 60kg bombs
  • 144 – 30kg bombs

  • Aviation gas – 2,320 tons

    Operation History:
  • June the 14th, 1941 - Commissioned; the Hiryo was the best kept secret of the IJN to that point. She cruised around Mutsu Harbor for several months.
  • November 1st, 1941 – The ship is introduced to the outside world, running her official trials in Tokyo Bay. The Western powers were outraged at the deception and stealth of her beginnings.
  • December 7th, 1941 – She, along with six other Aircraft Carriers of the IJN, attack Pearl Harbor, thus participating in the opening moves of the Pacific War.
  • Early 1942 – She raids into the Indian Ocean attacking the British in Ceylon.
  • May 7th and 8th, 1942 – Battle of the Coral Sea – Hiryo, Shokaku and Zuikaku battle with the Yorktown and Lexington in the first carrier versus carrier battle in history. The Americans manage to escape the overwhelming air attacks on the eve of the 7th. On the 8th the Lexington is caught in the early morning by the full weight of the strike force. 89 Kate (VT) descend on the helpless carrier as the 92 Zero (VF) escorts swat the American CAP from the sky. The Lexington is hit no fewer than 12 times and the first Japanese force withdraws. Thirty minutes later the second strike arrives. 89 Val (VB) dive bombers and their 45 escorting Zeros (VF) descend on the Yorktown. As the dive bombers begin lining up their attacks the Yorktown slips into a rain squall. Three direct hits from 250kg bombs rock the carrier. The remaining Vals turn their attention to the escorting ships that were not so lucky to find shelter in the rain. The Japanese retire their aircraft.

    The Japanese were not the only ones to get off a strike force. The American force of 34 (VT), 34 (VT) and 34 Wildcats (VF) find the Japanese main force before the first IJN strike wave has returned. They are greeted by a large CAP of 18 Zeros (VF). The American VBs are hammered as the USN VTs slip past the Japanese CAP. No less than four torpedoes slam into the Hiryo and the Shokaku receives two as well. The USN VBs manage to plant a single 500lb bomb into the forward deck of the Shokaku.
  • American losses:
    • U.S.S. Lexington sunk
    • U.S.S. Yorktown heavily damaged
    • 2 USN Heavy cruisers sunk
    • 4 USN destroyers sunk
    • 28 VB shot down
    • 21 VF shot down
    • 15 VT shot down
  • Japanese losses:
    • Hiryo heavily damaged
    • Shokaku heavily damaged
    • 1 Heavy cruiser moderately damaged
    • 7 VB shot down
    • 9 VF shot down
    • 10 VT shot down
  • June 23rd, 1942 – Enters Aomori Harbor for repairs
  • September 12th, 1942 – Repairs complete
  • April 4th, 1943 – Returns to Aomori harbor for reconfiguration. At this time her aircraft complement is reduced to 160 attack aircraft plus 25 Myrt recon craft. Her forward lower hangar is converted into extensive repair facilities for aircraft and extended crews quarters.
  • 0645 hrs - August 1944 – Before the Mariana debacle began a lone USN submarine fires a full spread of six torpedoes at the Hiryo. The first passes in front of the ship, continuing on and striking the Taiho. The remaining 5 torpedoes tore into the starboard side fore. The bow of the ship from 100’ aft to 600’ aft was opened completely. The ship careened to starboard and took on tons of sea water. The order to reverse engines was given in the vain hope to reverse course and empty the hull of some of the water now filling her guts. The order had barely been given when the ship shuddered. Electrical power was lost and the ship began lowering by the bow at an alarming rate. Within 30 minutes the chrysanthemum was awash. The order to abandon ship was given.
  • 0745 hrs – August 1944 – The Hiryo sinks.

  • Special Notes:
    At 1200 (365.76 meters) feet long overall the structural strength of the hull was the first major concern. Two options presented themselves: Allow for certain levels of hull flex or reinforce the keel extensively. One or the other had to be adopted lest the ship break in half in heavy seas. Unfortunately allowing a flex to the length of the hull was quickly dismissed. A warship (especially a flat decked carrier of her size) could not be afforded a “weak” hull, which was what a flex hull basically was. Over 15 tons of steel went into the reinforcement of the keel of the ship.

    Aircraft handling was another major concern. With over 250 aircraft for a complement the standard 3 elevators would not suffice. Six elevators were planned – five finally adopted - as were large aircraft repair facilities and enormous magazines and avgas storage. The Hiryo could refuel other aircraft carriers with both fuel oil and avgas during operations.

    The construction yards built to construct and berth the Hiryo in Mutsu Bay (Named Aomori Harbor) were also used to build the Yashima.

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