The Beechcraft L-23/ U-8 Seminole was a general utility aircraft that remained in US Army service for four decades, from the early 1950s to the early 1990s.
The L-23 was originally a military version of the Beech Model D50B Twin Bonanza executive transport. Four standard Twin Bonanzas were ordered for evaluation early in 1952, becoming the YL-23. The Twin Bonanza was a low winged monoplane, powered by two Lycoming piston engines. It had a flat sided fuselage with a rather bulbous profile when seen from the side. It had a slightly odd shaped wing – the leading edge tapered from the wing root to the engine nacelle, then again on the far side of the engine, but the outer panel was almost straight. The trailing edge was straight from the fuselage to the nacelle then tapered towards the wing tip.
The YL-23 was ordered into production, starting with the L-23A of 1952. It was used as a general transport and utility aircraft, although one version was used for experiments in electronic warfare. All but one of the military machines were used by the US Army, and it was adopted with some enthusiasm – by the end of 1953 it was to be found all across the US, and in Army bases in Europe and the Far East, arriving just in time to play a part in the later stages of the Korean War.
The USAAF ordered the single XL-23C, but didn’t take any further machines.
In 1962 all surviving aircraft became the U-8, but otherwise keep the same type letters, so the L-23D became the U-8D.
Fifty five examples of the L-23A were produced. They were powered by the 260hp Lycoming piston engine, and used a two blade wooden propeller.
The L-23B was similar to the L-23A, but with a two blade metal propeller. A total of 40 were purchased, starting in 1954.
One example of the XL-23C was purchased for USAF evaluation
The L-23D was based on the Model E50 Twin Bonanza, which used a 340hp Lycoming engine. Work began on the design in January 1955, it made its first flight in October 1955 and the first of 85 built from new was delivered in November 1956. Another 93 L-23As and L-23Bs (from the original total of 95) were later converted to the L-23D standard. The new engines saw the aircraft’s top speed rise from 180mph to 233mph and its service ceiling from 24,300ft to 27,000ft. The L-23D was the fastest of the standard piston engine powered versions of the aircraft.
The RL-23D was the designation given to a number of aircraft used as ELINT aircraft. Sources differ on the exact number produced, varying from a low of eight to as many as thirty. The first aircraft were produced in 1959-60. Two were given the Motorola APS-85 Side-looking Airborne Radar system in 1959, designed to allow the aircraft to fly along the neutral or allied side of a hostile border and using its radar over the line. Another sixteen were give the Texas Instruments AN/APQ-86 SLAR, starting in 1960. Both systems carried their antenna in long ventral pods under the fuselage.
One aircraft was used to test the AN/APD-1 ground surveillance radar and another the nose-mounted AN/AVG-50 weather avoidance radar.
The designation L-23E was given to six commercial Model D50 Twin Bonanzas that were ordered in 1956. They used a less powerful 295hp Lycoming GO-480-G2D6 engine than the L-23D, and were thus somewhat slower.
The L-23F was a military version of the Beech Model 65 Queen Air. This had a deeper fuselage than the Twin Bonanza, and could carry two crew and seven passengers. The L-23F used similar 340hp engines as the L-23D. Three were ordered for evaluation in 1959, and they were followed by seventy-six production aircraft. In the 1980s those aircraft still in service with the National Guard were given more powerful engines, new engine mounts and three bladed propellers. Well over half of the original aircraft had been modified by 1986. These aircraft were significantly different to the earlier variants, with wider wings, and a longer and redesigned fuselage.
The designation U-8G was given to earlier U-8D, RU-8D and U-8F aircraft that were given a more modern version of the Lycoming O-480 engine and modified to carry six passengers.
The NU-8F was the designation given to a single Queen Air that was used as the prototype of Beechcraft’s turbo-prop powered King Air 65-90. The NU-8F was powered by two 525shp Pratt & Whitney of Canada PT6A-7 turboprops, and was by far the fastest member of the family, with a top speed of 290 mph.
Engine: Two Lycoming O-480-1 engines
Power: 340hp each
Crew: 2, six passengers
Span: 45ft 3.5in
Length: 31ft 6.5in
Height: 11ft 4in
Empty weight: 4,974lb
Gross weight: 7,300lb
Max speed: 233mph
Cruising speed: 203mph
Climb Rate: 1,560ft/ sec
Service ceiling: 27,000
Range: 1,355 miles