MARTIN JRM MARS FLYING BOATCOMMERCIAL PROJECTS OF 1944

Jared A. Zichek

A MERICAN A EROSPACE A RCHIVE 1

The American Aerospace Archive is published periodically by Jared A. Zichek (6021 La Jolla Hermosa Ave, La Jolla, California 92037) and is printed and distributed by MagCloud (www.jaredzichek.magcloud.com). American Aerospace Archive Number 1.01 (ISSN 1943-9636) is copyright 2008 by Jared A. Zichek. All rights reserved. All featured text and images are copyright 2008 their respective copyright holders. Reproduction of any material in part or in whole without its creator's permission is strictly forbidden. The Ameri-can Aerospace Archive accepts no responsibility for unsolicited manuscripts, photos, art or other materials. Submissions are considered on an invitational basis only. Email your comments and suggestions to editor@aeroarchivepress.com and visit our website at www.aeroarchivepress.com.

ABOVE: Title page of the lavish 1944 marketing brochure for the commer-cialized Martin JRM Mars Flying Boat. The original document was printed in an oversized, landscape format and has been adapted to fit the smaller con-fines of this publication. The brochure was found in the National Archives, RG 72, and all images and information pre-sented herein originate from it.

COVER: Artist's impression of the com-mercial Martin Mars Transport in pseu-do-Pan Am markings.

offered superior economy, safety and dependability. Half of the Mars' gross weight was disposable load. It offered great capacity for cargo and greater comfort for passengers than any other existing airplane. The first Martin Mars had already set many world records; the commercial version was capable of ex-ceeding them.

General Description

The Mars Transport possessed great load carrying capability, tremendous size, and economy of operation. Its normal gross weight was 165,000 lbs. The two-deck hull alone—exclusive of the wing—contained 15,600 cubic feet within its 120 foot length. Translated into terms of transport, the Mars had ad-equate space to carry the enormous load of 25,500 lbs of cargo and 105 passengers for a distance of 1,500 statute miles or 9,050 lbs of cargo and 60 passengers for a distance of 3,500 miles.

The Mars featured a semi-mono-coque constructed hull. Four main water-tight bulkheads, closely spaced former frames and stringers provided the strength for the Mars' load-carrying ability. All sheet material in the wing and hull was 24 ST or SRT alclad aluminum

alloy. Stringers were either of formed al-clad sheet or extruded 24 ST material.

The Mars was a high-wing type of flying boat. The wing was of the time-proven, two-spar type with stressed skin cover. Both spars were of the tension field type, with no cut-outs except where access holes were provided for passage of the crew. Both top and bottom covers were of the flat sheet-stringer type. The upper cover was unique in that the cover gauge and string spacing were adjusted so that no wrinkles appeared in the skin at full design load. The nose skin was also designed to be non-wrinkling at 1.5 times the flight factor.

In 1944, the Martin Mars was the larg-est and longest-range production fly-ing boat in the world. Initially con-

ceived in 1938 as a patrol bomber, the type was subsequently converted to the transport role. The marketing brochure reproduced over the following pages presents several interior designs for a commercial version—all-passenger, all-cargo, and passenger-cargo arrange-ments. Martin claimed that "competent authorities" recognized these arrange-ments as "outstanding contributions to modern transportation."

By 1944, the Martin Mars prototype had been built, tested, and largely prov-en. It was in over-ocean service with the US Navy, carrying war materiel and troops. Twenty more were being rushed to completion for the Naval Air Trans-port Service—then one of the two largest airlines in the world, the other being Pan Am, the main target of Martin's market-ing efforts. (This order was later reduced to 5 at the end of the war).

The Mars Transport was the climax of years of Martin's development and experience in the design and building of flying boats; the aircraft offered "new and practical horizons" to those who were "planning the air lines of peace."

Martin claimed that the flying boat

2

Additional payload space was pro-vided in the cargo bays built into the wings. These bays were readily acces-sible by the use of ingenious elevators which hoisted cargo into the wings.

The vastness of the Mars was matched by its rugged strength. In stren-uous tests and full load dives the Mars had withstood strains of upwards of half a million pounds on its wing. The hull bottom had resisted equally heavy loads and impacts in landing in high seas. In structure as well as in design, the Martin Mars Transport incorporated the most advanced developments in aviation ex-perience.

Unfortunately for Martin, airlines were not convinced by the company's marketing prowess, preferring the economy and practicality of land-based airliners over large flying boats in the postwar era. Furthermore, the concept of the "flying hotel" would be superseded by less luxurious high volume passenger service targeted at the middle class. The JRM Mars would go on to serve the Navy admirably in the transport role until 1956, with only one being lost in an acci-dent. In 1959, Flying Tankers, Inc. pur-chased the four remaining surplus flying boats and employed them in the water bomber role to control forest fires. As of 2008, two survive in this role with Coul-son Flying Tankers in British Columbia.

A man could walk erect within the six-foot thick center portion of the wing, which spanned an impressive 200 ft. Mi-nor adjustments to engine and accesso-ries could be made in flight. Power was supplied by four engines—each develop-ing 3,000 horsepower. The total 12,000 horsepower was more than three times that of a giant two-car diesel-electric lo-comotive.

Two complete decks extended al-most the full length of the hull. They provided flexible and economic use of the space for disposal of either pas-sengers or cargo. On the upper deck, forward of the front wing spar, was the flight deck—nerve center of the ship. This flight deck, 30 x 12 ft was com-parable to the bridge of a large surface ship, and provided accommodations for desks, instrument panels, comfortable chairs and everything necessary for the efficient operation of the ship and the comfort of the flight crew.

The remainder of the upper deck, and the entire lower deck were available for transport requirements—either pas-senger, or cargo, or both. Typical interi-or arrangements are pictured on the fol-lowing pages. Variations were possible, according to the need. The lower deck was specially stressed for heavy, concen-trated loads. The upper deck had abun-dant space for lower density cargo.

Thus, while it never became a luxurious commercial flying boat like the prewar Boeing 314, the Martin Mars ultimately found success in a more critical role that its makers never anticipated.

Sources:

The Martin Mars Transport Airplane, Baltimore: The Glenn L. Martin Company, 1944

3

Retouched (and possibly staged) photo showing the terrific load-carrying capability of the Martin Mars, in this case the twin tail XPB2M-1R. Initially conceived in 1938 as a "flying dreadnought" for ocean patrol, it was subse-quently converted to a transport when its original role was deemed obsolete.

Deck drawings of the De Luxe Sleeper version of the Martin Mars Transport. The face-to-face passenger seating and over-all roominess is noteworthy.

4

5

ABOVE: Passenger Entry. In boarding the Mar-tin Mars, passengers would have stepped from the landing dock directly onto the lower deck of the ship, entirely eliminating the need of outside ladders or steps.

RIGHT: Cargo Loading. Even in the De Luxe Sleeper version, large cargo doors would have allowed for the safe and rapid handling of heavy and bulky freight.

6