|Model 50 Twin Bonanza|
|operated by the US Army as the U-8 Seminole|
|Manufacturer||Beech Aircraft Corporation|
|First flight||November 15, 1949|
|Primary user||Private operators|
|Number built||975 (includes 195 L-23)|
|Developed into||Beechcraft Queen Air|
The Beechcraft Model 50 Twin Bonanza is a small twin-engined aircraft designed by Beechcraft as an executive transport for the business market. It was developed to fill a gap in Beechcraft's product line between the single-engined Model 35 Bonanza and the larger Model 18. The Twin Bonanza is dissimilar to the Bonanza, being much larger and heavier and using more powerful engines, while in its earliest form having only half the passenger capacity of the Model 18.
The Twin Bonanza was first flown on November 15, 1949 after rapid development, begun only in April of that year. The aircraft was first designed to use Franklin engines with superchargers, but engine company owner Preston Tucker diverted all of its aviation resources to support his ill-fated Tucker 48 automobile project, and the aircraft was hastily modified to accept the Lycoming GO-435. However, the engine nacelles were not redesigned to fit the smaller Lycoming, creating unusually generous internal clearances that facilitate engine maintenance. The Model 50's type certificate was awarded in 1951, and production began the same year.
The United States Army adopted the Twin Bonanza as the L-23 Seminole utility transport, making it the largest fixed-wing aircraft in its inventory at that time. According to Ralph Harmon, the airplane's designer, during an initial demonstration flight for the Army, Beechcraft test pilot Claude Palmer crashed while trying to land over a 50-foot (15 m) tree line with the aircraft full of soldiers and sandbags. Everyone on board walked away from the crash. The Army was impressed with the structural strength of the Twin Bonanza, eventually purchasing 216 of the 994 examples produced. It was also the first twin-engined aircraft in its class to be offered to the business market, but the Korean War was raging in the early 1950s and the US Army took almost the entire production for 1952 and 1953.
The Beechcraft Model 65 Queen Air and Model 90 King Air are both direct descendants of the Model 50 Twin Bonanza. All three aircraft share the same basic wing design, as well as landing gear, flaps, instrument panels, fuel cells, and more. The Queen Air added a larger cabin to the design, while the later King Air added turbine power and pressurization. Twin Bonanza production ended in 1963 while the King Air was under development.
The Twin Bonanza is an all-metal low-wing monoplane with a cantilever wing, initially powered by two wing-mounted Lycoming GO-435 piston engines, each with a wooden two-bladed propeller. The cabin seats six people on bench seats, three in the front and three in the rear accessed by a side door on the right side. To gain access to the door a retractable three-tread steps is used. The Twin Bonanza has tricycle landing gear with the nose wheel retracting rearwards and the main landing gears retracting partially into the engine nacelles, leaving the tires exposed to assist in the event of a belly landing. The 260 hp (190 kW) GO-435 was replaced by the 275 hp (205 kW) Lycoming GO-480 in 1954; this engine was subsequently upgraded with fuel injection and then superchargers, increasing power to 295 hp (220 kW) in 1956 and 340 hp (250 kW) in 1957.
Despite its name, the Twin Bonanza is a substantially larger and heavier aircraft that is mostly dissimilar to the single-engined Bonanza; the only major shared parts are the front fuselage sides and windows, and on early models, the main cabin door. The Twin Bonanza fuselage is 12 in (30 cm) wider than that of the Bonanza.
The Twin Bonanza had trouble competing with the similarly capable but substantially lighter Cessna 310 and Piper PA-23, so Beechcraft used the basic single-engined Bonanza fuselage and many other Bonanza parts to create the Twin Bonanza's effective replacements: the Travel Air and the closely related Baron. The Twin Bonanza has been plagued by a reputation for slow cruise speed, poor fuel economy and high engine overhaul costs relative to other six to eight-seat light piston twins; this has historically kept resale values low, but many owners praise its reliability, good outwards visibility, stable flying qualities and generous interior space, particularly when the three-wide seats are not fully occupied.
The Twin Bonanza is popularly known as the "Twin Bo" or the "T-Bone".
In January 2012 the Australian Civil Aviation Safety Authority issued an airworthiness directive grounding all Bonanzas, Twin Bonanzas and Debonairs equipped with a single pole-style yoke, having forward elevator control cables more than 15 years old, until they could be inspected. The AD was issued based on two aircraft found to have frayed cables, one of which suffered a cable failure just prior to takeoff and resulting concerns about the age of the cables in fleet aircraft of this age. At the time of the grounding some Bonanzas had reached 64 years in service. Aircraft with frayed cables were grounded until the cables were replaced and those that passed inspection were required to have their cables replaced within 60 days regardless. The AD affected only Australian aircraft and was not adopted by the airworthiness authority responsible for the type certificate, the US Federal Aviation Administration. The FAA instead opted to issue a Special Airworthiness Information Bulletin (SAIB) requesting that the elevator control cables be inspected during the annual inspection.
There have been numerous accidents and incidents involving the Beechcraft Twin Bonanza. Listed below are a select few of the most notable ones.
Data from Jane's All The World's Aircraft 1956–57
Aircraft of comparable role, configuration, and era
Media related to Beechcraft Twin Bonanza at Wikimedia Commons