Failure Knowledge Database / 100 Selected Cases

Sinking of the aircraft carrier Taihocaused by one hit of a torpedo
Oct. 20th, 2005, On the Pacific Ocean in the vicinity of Saipan island
KOBAYASHI, Hideo (Tokyo Institute of Technology)(Summary)
On June 19th, 1944, the aircraft carrier Taiho participated in the battle of Mariana as the main flag shipof the Japanese first fle et and launched its first at tack team.

Soon after the start of the battle, a torpedo

launched by the U.S. submarine Albacore hit the Taiho. This hit caused some of the fitting of the gasoline
tank to become loose, a nd volatile gas began to leak. Unfortunately, the aircraft hanger became filled byvolatile gas because t he front si de elevator was broke n by t he s hock of t he torpedo hit and i ts apert ure
blocked of f. After a few hours, the volatile gas ca ught fire and explode d. Finally the carri er becam e
engulfed in flames and sank.
The Taiho was constructed to be an unsinkable aircraft carrier. However, the defense on flight deck wasof no use w hatsoever. The defense method of gasoline tanks and countermeasure volatile gas leaking wasinadequate. J ust af ter t his accident, a n e mergency m easure beyond naval engineer's wildest dreams was
adopted to all fleets of Japanese imperial navy.
1. Component
Here is the specification of the Taiho.
Displacement capacity : 34,200 t
Length water line : 253 m
Speed : 333 knot
Aircraft capacity : 53
The Taiho was called the strongest aircraft carrier ever made by the Japanese Imperial Navy. Kawasaki
Heavy Industry began construction of the Taiho in July 1941 at their dock in Kobe. For the construction of
the Taiho, the engineers implemented countermeasures obtained from lessons learned during combat in thewar.
As a result of the construction as rapidly as possible, the Taiho was finished in March 1944. Therefore,
the Taiho was expected to be the most effective vessel for actual combat in all regards.
2. Event
Kawasaki Heavy Industry began construction of t he Taiho in J uly 1941 at t heir dock in Kobe. For theconstruction of the Taiho, the engineers im plemented co untermeasures ob tained fro m lessons lear ned
during combat in the war. As a result of the construction as rapidly as possible, Taiho was finished in March
1944. Theref ore, Taiho is expect ed as the most effective for a ctual fight at all points. The T aiho is adefensive aircraft c arrier, and i ts duty w as t o co ntinue a n o peration in t he b attlefield longer than other1

Failure Knowledge Database / 100 Selected Cases

aircraft carriers. The Taiho w as d esigned carry suc h a large am ount of b ombs and gas oline t hat it c ould
supply them to airplanes carried in other aircraft carriers. As a result, the aircraft capacity of the Taiho wasdecreased in exchange for the capacity to carry bombs and gasoline.
In June 19th, 1944, the aircraft carrier Taiho participated in the battle of Mari ana as the main flag shipof the Japan first fleet and launched its first attack team. Soon after that, at 8:10, a torpedo launched by the
US submarine Albacore hit the Taiho. The torpedo hit the outer plate of the Taiho's front gasoline tank, andits explosion ease away the deck joint on the tank, causing volatile gas to begin to leak and fill the hanger
space. However, this hit did not result in critical damage to the Taiho herself, and the Taiho's speed did not
decline.
Unfortunately, the front elevator was broken by that torpedo hit so that it was stopped on the way to thedeck whi le carrying aircraft for the sec ond at tack team. As the elevator pl aced a t f ront s ide of t he fl ight
deck was opening its hatch, it was im possible t o ei ther launc h t he s econd attack t eam or accomm odate
returning a ircraft of the fir st a ttack te am u ntil the hatch was closed. Bec ause of t he haste in cl osing thehatch by using possible running repairs, the ventilation in the hanger was restricte d and vol atile gas fil led
the hanger. A fter a few ho urs, the volatile gas w as i gnited by som e ig nition so urce, an d t he r esulting
explosion blew apart the ship in an instant, engulfing the ship in flames. All fire extinguishing devices werealso destroyed by the explosion, and as the fire spread, the ship gradually leaned and sank.
The Taiho was constructed to be an unsinkable aircraft carrier. But the defense on flight deck was of nouse whatsoever. However, this was not the main cause of the wrecking of the Taiho. The measures taken toprotect the gasoline tanks and prevent volatile gas for leaking were inadequate. Just after this accident, anemergency measure beyond naval engineer's wildest dreams was adopted to all fleets of Japanese imperial
navy. The m ethod called sink-preventing method or bu oyancy-keeping m ethod in or der t o cha nge
engineer's way of thinking.
The disaster of the first fleet was not the only example of this failure. At 11:20 a.m., after the launching
the second attack team, the aircraft carrier Sho-kaku was also torpedoed by the US submarine Cavilla, anda hit of three torpedoes caused catastrophic fires. The Sho-kaku sank at 2:01 p.m., before the sinking of the
Taiho.
3. Course
The primary requirement for the Taiho by the Japanese Imperial Navy was t o be an aircraft carrier that
could participate in a ba ttle for a lon g time at the fron t line without losing its flight deck function even if
the ship were to be attacked.
Because an aircraft carrier has a lar ge body, its flight deck is a go od target for enemy aircraft. Just one
direct hit of a bomb on the flight deck is adequate to destroy the function of the aircraft carrier. In fact, thiswas proven to be true with the regular aircraft carriers of the Japanese Imperial Navy in the Battle of theCoral Sea, the Battle of Midway, and the Battle of Santa Cruz Island.
The requirements for the Taiho also included the ability to accommodate the aircraft from other aircraft
carriers w ere damaged, w hich m eant t hat the Taiho h ad to be ab le to lo ad en ough fu el an d weap ons t o2Failure Knowledge Database / 100 Selected Cases

relaunch the aircraft that had lost their own mother ship. An ordinary aircraft carrier only carries enoughfuel and weapons for its own aircrafts, so this point is a big difference between the Taiho and other aircraft
carriers before her. In summary, the Taiho was constructed as a novel aircraft carrier that could carry a large
amount of fuel and weapons and that could maintain the function of its flight deck even when under attack.
In order to accommodate these new features, the Taiho's aircraft capacity was reduced to 52. This number isslightly less than that of regular aircraft carriers.
In the construction of the Taiho, the dock engineers focused on the defense of the flight deck. In thosedays, the weapons assumed to be used by the enemy were armor piercing bombs. This kind of bomb could
destroy th e a bility to l aunch an d la nd a ircraft if it e xploded on the fli ght deck. I nitially, th e Taiho was
required to s urvive hits by 25 0kg arm or p iercing b ombs, b ut la ter in t he pr oject th e re quirement w aschanged to 500kg bombs. In order t o fulfill this requirement, thick armor had to b e attached to the flightdeck. The flight deck of the Taiho had a length of 257m and a maximum width of 30m. It is impossible toattach th e ar mor on t his large area fro m a stabi lity and m obility standpoint. Therefore, t he engineers
attached armor plates on minimum area that was used as the airstrip (length:150m, width:18m). In order tosurvive a hit by a 500kg bomb, 75mm armor was required. The engineers also attached 20mm special steel
plates below the armor.
Aircraft were lifted from the hanger to the flight deck by elevator. The elevator space on the flight deck
was a square area 14 m eters in l ength, and this area was the we akest point of the T aiho. Regular aircraft
carriers have three elevators, but the Taiho had only two elevators placed on the front side and the rear side,
and armor plates were attached to those elevators. The armor attached on the elevators was 50mm thick andweighed 100tonnes. That is an unimaginable weight for a land elevator.
Attaching armor on t he fl ight d eck raised t he center of gravi ty of the s hip. T hus the hei ght fro m thewater surface was designed to be 12.51m.
The side armors were designed to hold against the horizontal hit of a 500kg bomb. The defense of theammunition storage area was designed to endure hits by the 8 inch cannon of heavy cruisers. Double walls
containing a space filled with liquid were used as defense against torpedo attack. Oil or water was used forthe liquid. Liquid is an incompressible fluid, unlike gases. When a torpedo hits the outer wall, the impact of
the hit is propagated by the liquid to a large area of the inner wall. Then the inner wall receives the force of
the im pact di stributed over a lar ge surfa ce area a nd this ef fect de cline a bout 30become so we ak. So t heliquid lay er r equire 9 0cm thickness. T he ex plosive of a t orpedo is usu ally 4 00kg, and t he T aiho's
underwater diffuse was enough to survive a hit by such an explosive.
The armor of th e sh ip be lly was edg ewise with a n u pper-side thickness of 1 85mm and a lowe r-side
thickness of 70mm. Under draft-line part of berry were the armor anglet against center line of the ship. This
armor prevented a torpedo from hitting the ship vertically, which reduced the damage of the hit.
The bridge was isl and sha ped and placed on the c enter of t he s hip. I n a ddition, a n angled verticalchimney structure integrated with the bridge structure was adopted.

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Failure Knowledge Database / 100 Selected Cases

4. Cause
It is impossible for a defensive aircraft carrier such as the Taiho to be sunk by the hit of a single torpedo.
The main cause of the sinking of the Taiho was the fire disaster.
The Taiho was constructed to be unsinkable; however, its special fight deck defense turned out to be of
no use whatsoever.

But this is not an accident. The defense methods used to protect tthe gasoline tanks

and the fire precautions taken against leaking volatile gas were insufficient.
5. Immediate Action
Before the sinking of the Taiho, the issue of appropriate fire defense measures was brought up. The fire
defense m easures co nsidered w ere rem oving com bustible m aterials an d i nstallation of a completely
equipped fire extinguish system. Those m easures were not uncommon for fi ghting ships, and conceivablecountermeasures w ere th ough to be done. H owever, after th e b eginning of t he Pa cific War, n o limit thatindicates ad equate fire d efense level w ere fo und from t he investigations of a l arge number of dam aged
ships. Since the beginning of war, at first paint was considered to be a problem. Initially, there were somecases where soldiers pe eled of f the pa int before aship participated i n a b attle. After a sh ort tim e

incombustible paint was developed, but it was insufficient in stickiness and rust prevention.
The aircraft carrier Jun-yo that participated in the battle of Mariana in June 1944 was based on a kind ofpassenger boat, a nd it used a l ot of w ood for stru cture. Bef ore t he bat tle, a lmost al l t hings of Jun-y oconsidered to be combustible were discarded.
After the b attle of Mariana, a st udy grou p c onsisting of experts fro m all div isions developed
groundbreaking countermeasures that were to be adopted in the inhabited area and so on. These ideas weresuggested by Major Hisaemon Sakuraba and were unimaginable in ordinary times. More specifically, they
were as follows:･ Do not use wooden products･ Peel off all paint and coat with Art Metal Cement･ Dispose of all linoleum without a few exception.
･ Hanging-floor storage are to be water-proof and used as fire defense water tank.
･ Publick room is to have only a side table for surgery, and all other furniture are to be detachable.
･ Beds in private rooms are to be folding type made from canvas.
･ Curtains are all to be disposed.
･ Soldiers room has only a table combined with a bed.
･ Soldiers place a mat on steel plates on which they take their meals and sleep.
Enhancements of fire ex tinguishing capabilities were also carried out. Movable pumps were added andfire ext inguishing t ubes we re exte nded in areas t hat were easily fl ammable. C oncerning aircr aft carriers,
there w ere many e xamples w here fires caused crit ical damage. As a resul t of the disabling of a l arge
number of air craft c arriers i n t he ba ttle of Mi dway, a bubble fire extinguishing sy stem w as adop ted as a
drastic c ountermeasure. A carbo n-dioxide gas fire extinguishing sy stem was ado pted f or th e h anger, but

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Failure Knowledge Database / 100 Selected Cases

when hanger was damaged, there were also opened hole then the effect of the system was little. Therefore,
the bu bble fi re ex tinguishing syst em t hat sprinkles bu bbles o f so ap liquid in to hanger fro m a nozzl e o f apump in order to put out fires was adopted.
6. Countermeasure
The clearance of combustible materials and completion of fire control equipment as fire precautions wasreviewed. In addition, the defense measures for protecting gasoline tanks in aircraft carriers were reviewed
from the lesson of the Taiho.
Gasoline tanks in aircraft carrier s were b asically armored, b ut aft er the ba ttle of Midway wa ter was
filled around the tanks. However, as a re sult of the l oss of the Taiho at th e battle of Mariana, the fact t hat
those methods were inadequat e was reve aled. Then engineers buil d up rebar st ructure i n this space a nd
fulfil concretes. In the case of the aircraft carrier Z uikaku, an emergency countermeasure that local bulge
were made at the outside of outer plate of gasoline tanks and fulfilled with concrete was taken.
At the same time, an instruction to minimize the load of gasoline and to dry completely empty gasoline
tank and close the gasoline tube was ordered. The ventilation system in the hanger was reinforced in order
to avoid accumulation of volatile gas.
After those countermeasures listed above were implemented, the battle of Ph ilippine sea took place. In
the b attle, t he Jap an Imperial Na vy l ost f our aircraft ca rriers, but each of t he s hips seemed to ha ve beenremarkably well reinforced against damage.
7. Knowledge
The cause of the wreck of the Taiho was inadequate protection of the gasoline tanks and inadequate fire
prevention m easures against vola tile gas. Soon after this acci dent, a emergency measure beyo nd naval
engineer's w ildest dreams was ado pted to a ll f leets of Jap anese i mperial n avy. The m ethod ca lled
sink-preventing method or buoyancy-keeping method in order to change engineer's way of thinking.
The great damage caused by the lost of four aircraft carriers at the battle of Midway and the loss of the
Taiho was avoidable if commanders did not find out but engineers did. This affair revealed a critical breachin w hich e ngineers te nd t o respond o nly to t he req uirements of t he commanders. Engineers m ust st udy,
have insightful view, and do things with a great deal of subtlety. The result of the wreck of the Taiho tells usthat the insights, foresights and subtlety of the engineers dominate the destiny of a nation.
If y ou ge neralized this af fair, y ou ca n fi nd the fac ts t hat th ere wer e d iremption between the a ffairs
countermeasured a nd the a ffairs really happene d. There w as the hi ghly defensive co untermeasure th atenables the aircraft carrier to battle and cruising even a t orpedo hit the ship, but there was no at tention to
the hit causes leak of volatile gas and that cause fire disaster which dimise the most important functions. A
lot of phenomenon are chained process and discovery of worst scenario is engineers' insight and foresight.
They identified the danger of volatile gas, but they had no countermeasures that focused on the process likeleak, congestion, inflaming, and explosion.
In ord er t o help engineers to st udy and have foresi ght, w e n eed t he establishment an d treatment t hat
enable those things. In addition, the opinions of the engineers should be given considerable attention. We
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Failure Knowledge Database / 100 Selected Cases

should n ot re peat t he fail ures in h istory. If w e rep lace c ommanders w ith em ployers, this less on can beapplied to the engineers of today's business world.
8. Primary Scenario
01. Poor Value Perception
02. Poor Safety Awareness03. Lack of Awareness of the Risk
04. Insufficient Analysis or Research
05. Insufficient Practice
06. Planning and Design
07. Poor Planning
08. Mismatching of Expertness
09. Usage
10. Operation/Use
11. Aircraft Carrier
12. Battle
13. Failure
14. Fracture/Damage
15. Hitting of a Torpedo
16. Secondary Damage
17. External Damage
18. Fuel Tank
19. Leakage
20. Explosion
21. Failure
22. Large-Scale Damage
23. Wreck
24. Loss to Organization
25. Social Loss
26. Weakening national defense

6Failure Knowledge Database / 100 Selected Cases

Aircraft Carrier Taiho

Fore part of a ship

Elevator
Flying-off deck

Fig. 1 The Draft of the Aircraft Carrier Taiho.

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