<p>Evaluated for the role of artillery spotting and front-line liaison, as were the Aeronca L-3 and Taylorcraft L-2, four examples of the Piper Aircraft Corporation's Cub Model J-3C-65 were acquired for this purpose by the US Army Air Corps in mid-1941. These were allocated the designation YO-59 and, almost simultaneously, 40 additional examples were ordered as O-59s. These were all delivered quickly enough for the US Army to employ them on a far wider evaluation basis than had been anticipated, using them in the field as if on operational service during annual maneuvers held at the end of 1941.
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<p>There was no doubt at all after this very practical test that the little Cubs were of more value than had been envisaged, and this useful experience made it possible to procure a new version more specifically tailored to the US Army's requirements. This, designated O-59A, was of braced high-wing monoplane configuration and was of composite construction comprising wooden spars, light alloy ribs and fabric covering. The fuselage and braced tail unit had basic structures of welded steel tube and were fabric-covered. Landing gear was of the fixed tailwheel type, and the powerplant of the O-59A comprised a 655-hp (48-kW) Continental O-170-3 flat-four engine. Primary requirement of the O-59A specification was improved accommodation for pilot and observer, which was achieved with a modified enclosure for the tandem cockpits to provide better all-round visibility.
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<p>Orders for this version totalled 948, but designation changes resulted in all becoming L-4As, the previously applied YO-59s and O-59s becoming L-4s. Subsequent procurement covered 980 L-4Bs with reduced radio equipment, 1,801 L-4Hs which had only detail changes, and 1,680 L-4Js which introduced a variable-pitch propeller that made a significant improvement to take-off performance. In addition to the various L-4 Grasshoppers procured specifically for the US Army, more than 100 were impressed from civil sources and designated L-4C (J-3C-65s), L-4D (J-3F-65s), L-4E (J-4Es), L-4F (J-5As), and L-4G (J-5Bs). Those impressed for use in Panama received the designations UC-83 (four J5As), UC-83A (two J3Ls) and UC-83B (one J4A).
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<p>In 1942 Piper was requested to develop a training glider from the basic L-4 design, this involving the removal of the powerplant and landing gear. In its modified form it had a simple cross-axle landing gear with hydraulic brakes, and the powerplant was replaced by a new front fuselage to accommodate an instructor, and he and both pupils were provided with full flying controls. A total of 250 was built for the USAAF under the designation TG-8, plus three for evaluation by the US Navy which designated them XLNP-1.
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<p>Apart from the three XLNP-1s which the US Navy acquired for evaluation, this service also procured 230 NE-1s, basically similar to the US Army's L-4s, and these were used as primary trainers. Twenty similar aircraft procured at a later date were designated NE-2, and 100 examples of the Piper J-5C Cub which were acquired for ambulance use (carrying one stretcher) were originally HE-1.
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<p>L-4 developments included the YL-14, of which five were produced. This was an enlarged three-seater with a 130-hp O-290-3 engine, but plans for 845 production L-14s were cancelled. The L-18 and L-21 were military versions of the PA-18 Super Cub, primarily for US Army use from the early 1950s, but a handful served in USAF colours, and many more were operated by the USAF civil flying schools in civilian colours.
<item><hi format=bold>Performance:</hi> maximum speed 85 mph (137 km/h); cruising speed 75 mph (121 km/h); service ceiling 9,300 ft (2,835 m); range 190 miles (306 km)
<item><hi format=bold>Weights:</hi> empty 730 lb (331 kg); maximum take-off 1,220 lb (533 kg)
<item><hi format=bold>Dimensions:</hi> span 35 ft 3 in (10.74 m ); length 22 ft 0 in (6.71 m); height 6 ft 8 in (2.03 m); wing area 179 sq ft (16.63 m<su>2</su>)
