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The discovery of the Japanese midget submarine in 2002 served not only to bring an important heritage resource to light, but also to focus attention on the many other deep water resources in the vicinity of Pearl Harbor. These wrecks are newly discovered elements of our national heritage.

Bow of Martin  Marshall  Mars, inverted on seafloor
Bow of Martin Marshall Mars, inverted on seafloor (Photo: Hans Van Tilburg, NOAA NMSP)

In December of 2004, a joint agency team surveyed an area around the site of the Japanese midget-sub discovered by the Hawaii Undersea Research Lab in 2002. Pisces Submersible pilots Terry Kerby and Max Cremer, and NOAA maritime archaeologists Hans Van Tilburg and Kelly Gleason and Jeremy Weirich conducted non-invasive documentation of underwater shipwreck and aircraft crash sites. Also involved in the survey was Jon Jarvis, regional director of the National Park Service and Doug Lentz, Pearl Harbor National Park Service Superintendent. The survey featured U.S. Navy flying boats dating from as early as the 1930s. The dives in 2004 involved collaboration between NOAA's Marine Sanctuaries Program, NOAA's Office of Ocean Exploration, the Hawaii Undersea Research Lab, and the National Park Service.

One of four R-3350-8 engines (2400 hp), this one standing propeller down on the bottom.
One of four R-3350-8 engines (2400 hp), this one standing propeller down on the bottom. (Photo: Hans Van Tilburg, NOAA NMSP)

During the submersible dives, two significant aircraft sites were discovered and subsequently documented by the team. The sites represent the beginning and the end, the alpha and omega of the American flying boat era. A Keystone PK-1 patrol bomber, a bi-wing variant of WW1 designs, represents the early days of the flying boats. The World War II-era US Navy's large Martin Mars JRM-1, a giant flying boat with a 200 foot wingspan, represents the last days of flying boat designs.

In the decades before WWII naval aviation was in a formative stage. Flying boat squadrons stationed at Ford Island began operations in the 1920s with wooden and fabric biplane models. By the 1930s advances were being made with aluminum hulls and more powerful engines, but the bi-plane design of earlier days still predominated. Struts and wires supported the wings, and engine nacelles were situated separately from other components. Crews were exposed to the wind and elements. A number of different manufacturers produced important transitional versions of navy flying boats during the inter-war period. The historic hulls of these early craft now lie on the seafloor, intentionally scuttled in 1938 after years of Pacific service. The flaring hull sponsons and the open cockpits capture the features of the age. The squadron insignia, still sharp after decades under the sea, portrays the winking elephant of Patrol Squadron One, Ford Island. Design and document research identify these airborne boats as PK-1 patrol bombers, built by Keystone Aircraft Corporation in Bristol, Pennsylvania. Only 18 were ever delivered to the navy. Twelve of these operated out of Fleet Air Base Pearl Harbor between 1932 and 1938. These are the very same boats which participated in Advanced Base Operations throughout the Northwestern Hawaiian Islands and the remote Pacific, an era of testing and trials in naval aviation immediately preceding the outbreak of WWII.

Fuselage bow of an early flying boat (likely a Keystone PK-1) emerges from the darkness.
Fuselage bow of an early flying boat (likely a Keystone PK-1) emerges from the darkness. (Photo: Hans Van Tilburg, NOAA NMSP)

The wreck of the Martin Mars JRM-1 represents the other end of the technical evolution. By the 1940s flying boats like the PBM Mariner and the PBY Catalina had proven the concept of amphibious air operations for both transport and combat. The Glenn Martin Company of Baltimore Maryland capitalized on existing technology by creating the world's largest operational flying boat, second only to Howard Hughes H-4. With a wingspan of 200 feet, length of 117 feet, and the capability of lifting 25 tons of cargo and carrying that over thousands of miles, the JRM-1 Mars  was one of the most spacious and comfortable transport seaplanes to ever get airborne. Only five were put into service. These boats operated for years throughout the Pacific from Alameda Naval Air Station as part of Transport Squadron Two, each named for the area covered (i.e. Philippine Mars, Marianas Mars, Caroline Mars, Hawaii Mars, Marshall Mars).

The Martin Mars flying boats had a near perfect operational record, covering the equivalent of 23 round trips to the moon, and accumulating more than 87,000 hours of safe passage. Only one incident exists as the exception to this record. On April 5th, 1950, the Marshall Mars was carrying out a short test flight for a new number three engine. Only minutes from Honolulu, oil could be seen streaming from the engine nacelle, and a fire had broken out. Unable to extinguish the blaze, LCDR Glenn E. Simmons brought the Marshall Mars down for a safe landing just south of Pearl Harbor, and the crew abandoned ship. Crash boats on the scene were also unable to put out the fire, and the Mars exploded in a spectacular eruption. Fortunately, no lives were lost.

Martin Mars buno 76822 at sea and on fire, April 5th 1950.
Martin Mars buno 76822 at sea and on fire, April 5th 1950. (Photo: Official US Navy photograph)

The remains of the Martin Marshall  Mars now lie 1,200 feet underwater. The bow and forward section of the hull are inverted, the currents slowly scouring sediments from beneath the cockpit. A portion of the wing and three of the four engines rest a short distance to the south.

Just a few miles south of Pearl, NOAA researchers and their National Park Service agency partners are beginning to get an idea of what s been hidden for so many years on the seafloor. Hawaii had a special role to play in the development of naval aviation and the events of WWII. Aviation history in the Pacific is so much a part of the history of Ford Island NAS and the history of Pearl Harbor that the stories are inseparable. These sites record that history and bear testimony to the commitment and sacrifice made during those years.

Additional Resources and Links

Martin Mars News Story
Maryland Aviation Museum

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