A Detailed Look At The Martin JRM Mars: The Largest WWII-Era Production Allied Flying Boat

It was in August 1938 when the U.S. Navy first granted Glenn L. Martin Aircraft Company to create a brand-new flying boat, which could have parallel uses as a slow-moving patrol bomber. The spectacular JRM Mars was of record-breaking size, being the largest military flying boat ever produced and to serve in the U.S. military. The Martin JRM Mars spent most of its life nestled in the Canadian Fire Services, battling never ending blazes across the forests of British Columbia.

The Martin JRM Mars sure did pack a powerful punch compared to the smaller but similar Fire Boss. The JRM was able to unload 27,276 gallons of water in a couple of seconds – enough to cover 4 acres of burning land – in comparison to the 819 gallons a single Fire Boss could release.

The Martin JRM Mars was the largest WWII-Era Production Allied Flying boat in history, and here’s everything you need to know about it.

The Martin JRM Mars Was Heavily Inspired By The PBM Mariner


When compared to the PBM Mariner, the JRM Mars was viewed as its evolutionary successor by the team at Glenn L. Martin. The initial prototype, known as the BuNo1520 was ready in November 1941. This rudimentary version was slightly different from the final product as it carried twin mega vertical tails, which would later be removed.

December 1941 saw the prototype put to test during taxi testing, where the BuNo1520 suffered a catastrophic end when one of the propellors malfunctioned, causing a leaking fuel tank which subsequently caused an engine to set alight. Following the disaster, repairs would be delayed, as two days later the USA entered World War II following the Japanese attack on Pearl Harbor.

As the war raged on, advances in military technology developed at a rapid rate, with the long-awaited JRM ready for action. Slow-moving bombers were a thing of the past, with larger warplanes boasting extra speed and range replacing them. As the Martin JRM Mars, now given the new moniker XPB2M-1R, was not designed with the sole purpose of unleashing bombs, the US Navy decided that it would be more useful as military transport. With this decision came some clever modifications – its wing bomb bays, gun turrets, and armored plating swapped for cargo hatchings and loading equipment.

The Martin JRM Mars Was The Best Flying Boat The World Had Ever Seen


The whopping size of the Martin JRM Mars must be well appreciated, with four 180-cylinder Wright R-3350 Duplex-Cyclone engines. The super flying boat came booming with 2,200 horsepower, and a top speed of 221-mph. The Mars could usually be seen zooming through the skies at its cruising speed of 190-mph, and an altitude of 14,600 feet, with a range of 4,949 miles.

Like other conventional flying boats, it had a huge, rounded hull and its flight deck was mounted high up, which offered an amazing range of visibility to ensure its pilots would drop the masses of water in the needed area. Its elongated wings were straight, with curved red tips, and were each fitted with a two-strutted pontoon to prevent it from tippling over into the water each time it picked a load up. The Martin JRM Mars had a cool special feature, being that after scooping up its 27,276-liter of water, it could then be turned into a foam by combining it with a chemical concentrate that sat in a separate tank.

The Martin JRM Mars Was A Fire-fighting Legend


During the mid to late 1950s, masses of forest fires were destroying western Canada’s land. These natural disasters were effectively destroying the Forest Industries Flying Tankers depot, which produced tankers that would combat this burning issue. Dan Mclvor, the chief pilot at Macmillian-Bloedel, recognized that there were very few airfields but an extensive number of lakes surrounding the affected area, which lead him to suggest a flying boat with cool fire-fighting capabilities may be the solution to their growing problems. The Martin JRM Mars was the perfect solution, and in the 1960s the 6 JRMs were completely refurbished at Victoria Airport by Fairway Aviation. Engineers worked tirelessly to remove all unnecessary features which were originally fitted to maximize its military transport potential. The Martin JRM Mars flying boat were furnished with massive water tanks which were well-filled by a striking retractable scoop system – transforming the JRM into an aerial fire-fighter superstar.

There is one final flight-worthy Martin JRM Mars remaining and has been given the nickname ‘Hawaii Mars’. This massive beast is up for sale towards the end of 2022, and if you were interested, a gigantic lake is a must! This fire-fighting legend broke boundaries during its serving days and aided the US Navy in tremendous ways. Hopefully, its next keeper can treat this piece of legendary history with the appreciation and respect it deserves.

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