Dive discovers missing aircraft hangar of sunken WWII-era Japanese submarine

April 28, 2015  |   |  9 Comments
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The dramatic discovery of a lost World War II-era Imperial Japanese Navy mega-submarine by a University of Hawaiʻi and U.S. National Oceanic and Atmospheric Administration (NOAA) team in December 2013 inspired a new search by NHK, the Japanese Broadcasting Corporation, to find key missing pieces of the battleship.

The recent survey, the first to return to I-400 submarine since its discovery, successfully located, mapped and captured on video for the first time not only the submarine’s hangar and conning tower (navigation platform), but an unexpected and significant new discovery—the submarine’s bell. Torn from the submarine by the explosive forces that broke apart and sank I-400, the bell lies close to the conning tower on the seafloor.

I-400 hangar

World War II-era Imperial Japanese Navy mega-submarine I-400 hangar door

The massive aircraft hangar, large enough to launch three float-plane bombers, was the defining feature of the I-400. After the end of the war, the I-400 was deliberately sunk at sea outside of Pearl Harbor to keep its technological innovations safe from the Soviet Union.

“We didn’t have detailed enough bottom mapping data to help locate the hangar, conning tower and other signature features missing from the wreck of the I-400,” said Terry Kerby, operations director and chief submarine pilot of the Hawaiʻi Undersea Research Laboratory (HURL). “With only one dive day to try to find anything, we knew there was a strong chance we might spend the dive looking at the barren sandy bottom.”

Kerby continued, “We made a lucky guess where to start when we approached the main hull of the I-400 from the northwest. Our guess started to pay off when the giant hangar door came into view, followed by the conning tower and hangar. Many items were amazingly intact for something that had ripped out of the hull of a sinking 400-foot-long submarine.”

The survey was conducted in cooperation with NOAA’s Maritime Heritage Program in the Office of National Marine Sanctuaries, with NOAA’s Hans Van Tilburg joining the dives as project archaeologist.

“The Office of National Marine Sanctuaries has been a partner for over a decade with HURL on many of the amazing and significant historical and archaeological discoveries they have made off Oahu,” said James Delgado, director of the Maritime Heritage Program. “The waters off Hawaiʻi not only encompass an important part of Native Hawaiian culture, but are also a veritable museum of our maritime past. As America’s ocean science agency, we’re committed to working with partners like HURL and NHK to learn more, and to share more of what lies beneath the waves.”

The new I-400 footage will be shared in a 73-minute special television program to be broadcast nationwide in Japan on Wednesday, May 6.

HURL-NHK I-400 submarine survey

The recent survey, the first to return to I-400 submarine since its discovery, successfully located, mapped and captured on video for the first time not only the submarine’s hangar and conning tower (navigation platform), but an unexpected and significant new discovery—the submarine’s bell.


HURL video of I-400 initial sighting

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Category: Research

Comments (9)

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  1. I have researched and built 1/72nd scale models of the I-401 and its aircraft. The Submarines built were with specific targets in mind. The first was to attack and bob the Panama Canal so that ships and supplies had to travel around the Horn or overland. The second was to use stealth and find and sink America’s Aircraft Carriers. The war for the IJN was over before the could be used. The USN converted all the Japanese language aboard to English, labeled all and then sailed the to Pearl Harbor. The sailing as well as the study research helped the Americans with Tech info For future use. However, the Russians were demanding one of them and unfortunately they had accidents and were sunk
    before the Russians could get them. (ie:scuttled in deep water)
    I have the model sub and photos if you would care to see them. It is a rare item now. Send me email and I will post Photos. You will be Amazed.
    Richard J. Melillo

    • JSpirit says:

      @Richard Melillo,

      I’d enjoy seeing that. I can’t see your email but you can email me at 64bit.jimmy [at] gmail [dot] com if you’d like.


  2. Le Lan says:

    I am currently writing an article on I-400 for a French magazine on submarines ( to see http://www.sub-marine-naval.com/ . Would it be possible to have your permission to publish my article in the pictures of your homepage and in particular that of the hangar door found at the bottom of the sea.

    Do you have other photograph of the wreck of I-400 in good definition that I could use?

    Best regards

    Jean-Yves Le Lan

    • Hello!
      Please find that the IJN submarine I-400 had an exact sister ship- the I-401. That is the submarine I have in 1/72nd scale of which the photos were taken. I would be more than happy to send you a disc of all the photos. Terry visited both subs.
      With this note, feel free to use these High Def Photos and just give me credit for them. I have boxes of research material for all the Imperial Japanese Navy submarines. I would be glad to share that information with you. Please send your email address, I will send a photo or two, also I can send a disc to you of all the photos with your mailing address.
      Be Happy to help!

      • Le Lan says:

        Dear Richard,

        Thanks for your answer. I traded with Terry Kerby and he sent me some pictures. But I want your photos well as those of Terry is not very good definition. Here is my e-mail address ; jy.lelan@neuf.fr .

        Tell me what I have to for the photo credit.

        Best regards


    • Yes, please contact me to discuss.

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