James Martin filed for his first retractable landing gear patent, No. 1,306,768, in June 1916, and it was issued three years later. He applied for a second patent, No. 1,418,008, on November 14, 1918, which was issued on May 30, 1922.

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Through a simple system of cables and pulleys, the undercarriage retracted directly backward and up. It drew the upper half of the spoked wheels into semicircular fairings alongside the fuselage, with a pair of underwing fairings behind the exposed part of the wheels for additional streamlining. The lower half of the wheels protruded underneath the plane. The patent examiner noted that the plane ‘may land with gear only partly extended.’

Martin’s was one of the few–if not the only–aircraft to feature retractable landing gear during World War I. One reason that retractable undercarriages were not more widespread at that time–or in the 1920s and 1930s, for that matter–was because the added weight of the retracting mechanism cancelled out the benefits of drag reduction. The K.III’s wing structure was comprised of one set of Martin’s novel K-shaped interplane struts plus two cabane struts attached to the front wing spar. A third cabane strut was fixed to the middle of the upper wing’s rear spar; it slanted downward and backward into the small headrest behind the cockpit. Ailerons were externally pivoted in the middle of the upper wings, which (excluding the ailerons) were shorter in span than the lower wings. Even with the protruding ailerons, the wingspan was only 20 feet 3 inches. The K.III’s fuselage, at 13 feet 4 inches, was even shorter than that of the Grain Kitten.

Retractable landing gear was not the only innovation that Martin saw fit to install in his Kitten. In anticipation of high-altitude combat, he fitted it with an oxygen cylinder and an electrical outlet into which the pilot could plug a special heated flying suit. Curiously, though, Martin never got around to installing any armament.

The airplane had a gross weight of 582 pounds, which was hauled around by a 45-hp engine. Martin’s performance expectations for his Kitten were singularly optimistic. He projected a top speed of 135 mph at ground level, 112 mph at 10,000 feet, and 97 mph at 25,000 feet. He also expected to upgrade the plane later with a 60-hp engine that would endow it with a speed of 145 mph at 10,000 feet.

It was not until December 1918, after the armistice had been signed and World War I concluded, that the K.III arrived at McCook Field for testing. The U.S. Army promptly rejected it as structurally unsound and refused to test-fly it until it was strengthened. When Martin flatly refused to allow any changes to be made on his original design, the Army dropped the K.III from consideration.

In January 1919, about a month after the K.III’s appearance at McCook Field, Martin delivered another design–a three-seat biplane bomber with a wingspan of 96 feet 3 inches, a length of 49 feet and a gross weight of 12,000 pounds. The bomber, which used the same K-shaped interplane struts as the Kitten, was ground tested with 400-hp Liberty engines, but it was never test-flown for the same reason the K.III wasn’t–the Army considered it structurally too weak to trust in the air.

Martin reacted by taking his case to Congress. Touting the exaggerated virtues of his fighter and bomber designs, he insisted that he had been unfairly treated by the Army. He managed to spark a congressional investigation in the 1920s, but it ultimately moved him no closer to having his strange planes test-flown, let alone accepted.

The Army soon lost its affection for the Kittens, but Martin subsequently went to the Navy to propose another of his designs–the K.IV, a less fragile-looking version of his original K.III. The K.IV’s fuselage looked similar to that of the K.III, but was longer (17 feet) and deeper, allowing the upper wing to be fixed to it directly, without cabane struts. The wings themselves had an equal span of 24 feet 2 inches, with conventional ailerons plus two sets of K-shaped interplane struts each. Empty weight was 686 pounds, and gross weight was 980 pounds. The plane had the advantage of more power, courtesy of a 60-hp, three-cylinder Lawrence L-3 engine.

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