From Aero Digest, April, 1935:
The Glenn L. Martin Company, Baltimore, Maryland
• President: Glenn L. Martin. Vice-president and Assistant General Manager: L. C. Milburn. Chief Engineer: B. C. Boulton.
Fifty-place closed high-wing flying boat.
Four Pratt & Whitney twin-row Wasp (geared) engines, 800 horsepower each. Span 130 feet. Length overall 90 feet 10.5 inches. Height overall 24 feet 7 inches. Wing area (including sponsons or “sea wings”) 2315 square feet. Power loading 15.9 pounds per horsepower. Wing loading 22 pounds per square foot.
Weight empty 23,000 pounds. Useful load 28,000 pounds. Payload varies with range. Gross weight 51,000 pounds. Fuel capacity 4000 gallons.
Maximum speed 180 miles per hour at 8000 feet. Cruising speed 155 miles per hour. Landing speed 70 miles per hour. Cruising range 4000 miles.
Hull: two step type, aluminum alloy construction, transverse bulkheads and frames, supplementary keelson, corrugated bottom skin and deck covering, smooth side skin. Four watertight bulkheads. Sponsons: riveted aluminum alloy, longitudinal and transverse framing, corrugated bottom skin, smooth top skin.
Wing: riveted aluminum alloy, braced center-section, cantilever outer panels. Box girder type primary structure with tension field web beams acting as side members, smooth stressed-skin bottom covering, corrugated sheet top with corrugations parallel to span and covered by thin smooth sheet. Stiffeners added to beam webs and former-ribs support corrugations. Nose ribs and metal leading edge covering attached to front beam. Tail ribs and fabric covering attached to rear beam. Balanced ailerons, metal framework, fabric covered. No flaps.
Tail group: Riveted aluminum alloy stub fin integral with hull. Wire braced stabilizer, detachable upper fin, riveted aluminum alloy framework, fabric covered. Balanced elevator and rudder. Hamilton Standard controllable-pitch propellers. Also see data in January, 1935, AERO DIGEST.