Operation Storm: Japan's Top Secret Submarines and Its Plan to Change the Course of World War II (15 page)

Meanwhile, the first test flight of Aichi’s special attack plane was held on November 8 that same year.
⁵
Lt. Cdr. Tadashi Funada was her chief test pilot. A highly respected member of the Flight Technology Test Group at Yokosuka, Funada was probably the foremost seaplane pilot in the Imperial Japanese Navy. And because of his extensive experience, he was as much involved in the plane’s design as in her flight testing.

Aichi’s special attack plane must have created quite a stir when she first rolled out of her top secret assembly building.
⁶
For one thing, experimental aircraft were painted bright orange,
⁷
and the plane was so big, her cockpit stood more than 15 feet off the ground. She was the largest aircraft ever carried by a submarine.

Aichi’s M6A1 was designed to do two mutually exclusive things: dive steeply to drop a bomb or come in low to launch a torpedo.
⁸
The first type of attack required “dive brakes,” which slowed a plane enough that it didn’t tear apart while diving. A torpedo attack, however, required a plane to fly low, straight, and fast. Each attack required different wing flap configurations and plenty of
practice to master. In other words, Aichi’s special attack plane was not for beginners. Then again, Funada was hardly a beginner.

It was a cold, gray day when Funada climbed into the cockpit. As he taxied down the nearby river, he looked forward to how the prototype would handle. But when he began climbing over Ise Bay,
⁹
he quickly realized something was wrong. The elevator controls on the plane’s horizontal tail stabilizer, which controlled the plane’s angle of climb or descent, weren’t working.
¹⁰
A plane losing elevator responsiveness is akin to a car losing its steering. That’s why Funada knew he had to make an emergency landing, and in a hurry.

The only way Funada could get the plane to descend was to throttle back her engine. As the plane’s speed decreased, she began dropping through the snow-laden clouds. Careful not to stall, Funada became conscious of another problem as he made his approach. Floatplanes are notoriously difficult to land. They tend to be nose heavy, and if pilots aren’t careful, they can easily flip over. Fortunately, Aichi had designed the aircraft to be less nose heavy than other seaplanes. As Funada eased back on the throttle, he felt the plane make contact with the waves. He had barely made it back alive.
¹¹

It might have been a successful landing, but it wasn’t a successful test flight. The ailerons had to be redesigned,
¹²
one of several aerodynamic problems that plagued the prototype.
^*
13
Another of the plane’s “x factors” was its floats. They were so large, the design team worried they’d create too much drag. The plane’s wing area was increased to provide more lift,
¹⁴
but there were also problems with the plane’s vertical stabilizer, which had to be lengthened to improve handling.
¹⁵
Unfortunately, the increased tail height meant the aircraft no longer fit inside the sub’s low-ceilinged hangar. At first Toshio Ozaki, the plane’s chief designer, considered making the tail assembly detachable.
¹⁶
But anything that had to be attached, like floats, required more time to assemble and launch the
plane. Ozaki fixed the problem by hinging the vertical stabilizer’s tip so it could be folded down, allowing the aircraft to fit inside the hangar. The plane’s horizontal stabilizers were also hinged for similar reasons.
¹⁷
It was an ingenious if simple solution, leaving the floats the only detachable element.

One of the unusual characteristics of the attack plane was its water-cooled engine. Most Japanese seaplanes relied upon an air-cooled engine, but a water-cooled engine offered several benefits. First, it enabled the plane to warm up inside the sub. This not only reduced the plane’s launch time—it minimized the time a sub had to be surfaced. Given that every minute increased the sub’s risk of discovery, this was an important improvement. A water-cooled engine also lowered the aircraft’s nose enough that it could fit inside the hangar. Additionally, it provided the necessary clearance between the propeller and the overly long torpedo the
Seiran
would have to carry, as well as better visibility from the cockpit,
¹⁸
an improvement
Sen-toku
pilots would come to appreciate.

The water-cooled engine was licensed from Germany’s Daimler-Benz, further refined by Japanese designers, and named
Atsuta
, after a local Nagoya shrine. Based on Daimler’s DB 601A engine, the
Atsuta
engine had 12 cylinders and delivered 1,400 horsepower at takeoff.
¹⁹
The
Atsuta
engine was not without problems, however. For one, lack of materials and poor metallurgy meant they required more maintenance than air-cooled engines. They also had a tendency to leak oil. As a result, it took a while before mechanics had the engine functioning properly, and even then it suffered from occasional problems. For now though, wing flaps, not the engine, were the main concern.

Aichi evaluated the special attack bomber against its own
Suisei
, since the plane was a naval dive-bomber too. Tests showed they had a similar rate of climb, but the combined weight and drag of the M6A1’s floats reduced its cruising speed. Without floats, the plane was specced to achieve a maximum air speed of 345 mph, more than the comparable Curtiss SB2C Helldiver. With floats, however, the plane’s performance was only 295 mph, comparable to the Helldiver’s top speed but still a substantial decline. The attack bomber’s
range was almost a third less than the
Suisei
. Fortunately, since the plane would be launched from a submarine close to shore, range was less important.
²⁰

Despite problems with the maiden flight, the navy was satisfied enough to order 44 aircraft.
²¹
Given the importance of the mission, however, the plane needed a proper name. The Imperial Japanese Navy didn’t always use utilitarian names when it came to its aircraft. Aichi’s
Suisei
means “comet” in Japanese;
Saiun
, a reconnaissance aircraft, means “painted cloud.” So, when Funada was asked by the Naval Air Command to come up with an appropriate moniker, he wanted something that did justice to the aircraft’s special mission. He named it
Seiran
.

Composed of two kanji characters,
Seiran
can be translated as “storm from a clear sky.” The name was inspired by an eighteenth-century woodblock print by Hiroshige.
²²
Called
Seiran of Awazu
, the print shows the village of Awazu after a storm with mist rising from a nearby mountain. Funada hoped that the
Seiran
special attack planes would surprise the enemy by suddenly appearing “like a ninja out of the fog.”
²³
Therefore the name was not only inspiring because of its glamour, it accurately captured its purpose as well.

As far as Japan was concerned, the United States had turned a blind eye toward her aspirations for nearly 40 years. When America wasn’t ignorning, belittling, or discriminating against Japan, she was seeking to hem her in. First the United States, Britain, Italy, and France had refused Japan a comparable-sized navy to limit her potential as a strategic rival; later the United States embargoed the precious oil that the IJN needed to function.

Nevertheless, the majority of Americans had been surprised by the attack on Pearl Harbor. Many of them had to look it up on a map to find out where it was. But if U.S. politicians had owned up to their machinations, they shouldn’t have been surprised at all. America had consistently underestimated Japan—whether out of arrogance, ignorance, or ingenuousness, it was impossible to say. Now Japan would launch a surprise attack on the Panama Canal in the same spirit as the attack on Pearl Harbor. If everything went well, America would be caught off guard again, and the Imperial
Japanese Navy would strike just as Funada imagined it: like a storm from a clear sky. It wasn’t just poetic, it was poetic justice.

The initial order for 44 aircraft included two trainers called
Nanzan
. Each
Nanzan
had hand-cranked landing gear rather than floats and dual controls for pilot training.
²⁴
Nanzan
were meant to replicate the
Seiran
flying experience, with several important differences. The
Nanzan
’s lack of floats meant the plane flew faster. Though the vertical tail stabilizer was shortened to compensate, it still handled differently.
²⁵
Nanzan
means “southern mountain,” but one source claims the plane was jokingly referred to as
Serian-kai
, which translates as “difficult childbirth.”
²⁶
Whether this name referred to the training experience or the problem-plagued production process is unclear.

Despite troubles with his first test flight, Funada fell in love with the
Seiran
. In his postwar memoir, he wrote, “I piloted many kinds of aircraft … [but] the
Seiran
’s … responsiveness and controllability was unforgettable. To me, it was a masterpiece.”
²⁷

This affirmation was to be echoed by many
Seiran
pilots, a testament to Aichi’s design skills. Ozaki and his team had not only built the world’s first sub-borne attack bomber, they’d built a plane that handled beautifully too.

W
HILE
S
EIRAN
FLIGHT TESTS CONTINUED
, F
UJIMORI WAS BUSY
at the Naval General Staff conducting research on the Panama Canal. Second only to Pearl Harbor, the canal was the most ambitious military installation the Japanese had ever targeted. But a lot of details were unknown, including the canal’s design, construction, and defenses.

The first thing Fujimori did was to get his colleague, Technical Maj. Gen. Ariki Katayama, to assign him three of his most capable engineers. Their job was to analyze everything Fujimori could find about the canal. Information was understandably scarce; not only had the canal been built more than 25 years ago, it was on the other side of the world.

Fujimori’s first bit of luck came when a Japanese engineer who’d worked on the canal provided him with a set of blueprints.
¹
His next was when an NGS colleague told him about an American at the Ofuna prison camp who had guarded the canal. During questioning, the prisoner revealed that the canal had been heavily protected after the attack on Pearl Harbor, but once the war shifted in the Allies’ favor defenses had been relaxed.
²

Fujimori and his team worked in utmost secrecy as they gathered information and quickly had a stack of documents more than a yard high. Weekly meetings were held in the NGS strategy room to review the canal’s topography and analyze its features.
³
One thing they learned was that the canal had been built to last. Hit by an earthquake only four days after it opened, the canal was undamaged, even though the quake was bigger than the one that had helped devastate San Francisco in 1906.
⁴

It had taken 34 years and two nations to build the canal.
^*
The largest engineering project ever undertaken at the time, the canal was considered a technological marvel along with the Pyramids and the Great Wall of China. It had two major lock systems: the Pedro Miguel locks on the Pacific side and the Gatun locks on the Atlantic.
^†

Fujimori realized that the locks were the most vulnerable part of the system and investigated attacking them from either the Pacific or the Atlantic side. A Pacific attack would offer an underwater strike force the best chance of concealment, since it was the most direct route from Japan. But Fujimori estimated it would take only a month to repair the locks on the Pacific side. However, if the Atlantic locks were destroyed, it could take up to six months to fix the damage.
⁵
Shipping would come to a standstill.

Destroying the Gatun locks wasn’t going to be easy. They were as much fortress as transit system. The three chambers were each 1,000 feet long, with concrete walls 45 to 60 feet thick.
⁶
Also, the topmost lock was only 110 feet wide, less than three times a
Seiran
’s wingspan. Any plane coming in for attack would have a narrow margin for error.

But Fujimori wasn’t as concerned about the locks, which appeared indestructible, as he was about their gates. It was their gates that had to be destroyed. Each lock contained double gates 65 feet wide, seven feet thick, and varying in height between 47 and 82 feet.
^‡
7
Built by a company specializing in steel bridge construction, the heaviest gate weighed 745 tons,
⁸
two to three times heavier than any lock gate ever built.
^§
Load-bearing parts like hinges were cast from vanadium steel, a durable alloy used to make car engines.
⁹
It would take more than one bomb to destroy gates like this.

Additionally, each lock had not just one but two sets of gates—one
behind the other in case the first set failed.
¹⁰
Each lock also had an intermediate set of gates for smaller ships, and there was even an emergency dam that could be lowered in case the gates failed.

One fact that improved their chances was that the lock gates were hollow.
¹¹
At least a bomb or torpedo wouldn’t have to punch through seven feet of solid steel. Nevertheless, destroying them would be a daunting task. At minimum eight main gates, three interim gates, and an emergency dam had to be broached to offset the system’s redundancy. Additionally, flying more than 30 attack bombers into such a narrow, well-defended area was asking for trouble. It would be hard enough getting the
Sen-toku
squadron within striking distance; concentrating all those bombers against three separate locks would be like Luke Skywalker flying against the Death Star.