|1957 Beechcraft D50 Twin Bonanza - N261B (sn DH-134)
Photo taken July 29, 2010 @ the
Oshkosh EAA AirVenture Fly-in, WI - USA (OSH / KOSH)
|Photo © Marcel Siegenthaler
The Beechcraft Model 50 Twin Bonanza was a small twin-engine 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-engine Model 35 Bonanza and the larger Model 18. The Twin Bonanza is about 50% larger than the Bonanza, has more powerful engines, and is significantly heavier, while in its earliest form having only half the passenger capacity of the Model 18.
The single-engine Bonanza is one of history's most successful civil aircraft, in production since 1947. Like many light aircraft, a twin-engine derivative was developed in an effort to improve performance, but that airplane was the Model 95 Travel Air (and later the Model 95-55 Baron, its descendant still in production till this day as the Model G58). The Twin Bonanza is not a true twin-engined derivative of the Bonanza since the cabin is wider and longer, however it did use some of the tooling jigs for the Bonanza as did the Travel Air (which was a closer derivative designed later).
The Twin Bonanza first flew on 15 November 1949 after a rapid development, only begun in April of that year. The Model 50's type certificate was awarded in 1952, 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 the inventory at that time. According to Ralph Harmon, the airplane's designer, during an initial demonstration flight for the Army, Claude Palmer, a Beechcraft Demonstration Test Pilot, crashed while trying to land over a 50-foot (15 m) tree line while 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-engine 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 descendents 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.
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 and that have forward elevator control cables that are 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 take-off 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 only affected 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.
- Model 50
Initial production version powered by two Lycoming GO-435-C2 engines, 13 built (6 for the US Army, remainder civilian versions, with the first 2 production numbers for factory evaluation). As of 2010, only one Model 50 is still registered & flying (serial number H-7).
- Model B50
Upgraded Model 50 with increased take-off weight, extra cabin windows and improved cabin heating, 139 built (40 for the US Army).
- Model C50
Superseded the B50; fitted with 275 hp (205 kW) Lycoming GO-480-F1A6 engines, 155 built (one to United States Air Force).
- Model D50
Superseded the C50; fitted with 295 hp (220 kW) Lycoming GO-480-G2C6 engines, 154 built (six to US Army).
- Model D50A
Upgraded D50 fitted with GO-480-G2D6 engines, 44 built.
- Model D50B
Upgraded D50A with new passenger steps and improved baggage area, 38 built.
- Model D50C
Upgraded D50B with starboard airstair entry door, three rows of seats, improved air conditioning, larger baggage area, 64 built.
- Model D50E
Upgraded D50C with extra port side window, squared-off rear starbord window, pointed nose and 295 hp (220 kW) Lycoming GO-480-G2F6 engines, 47 built.
- Model E50
Supercharged version of the D50; with increased take-off weight and 340 hp (250 kW) super-charged GSO-480-B1B6 engines, 181 built (mostly for the US Army).
- Model F50
Supercharged version of the D50A with GSO-480-B1B6 engines, 26 built including one converted to G50 standard.
- Model G50
Supercharged version of the D50B with 340 hp (250 kW) IGSO-480-A1A6 engines, increased fuel capacity and increased take-off weight, one conversion from F50 plus 23 built.
- Model H50
Supercharged version of the D50C with increased take-off weight and IGSO-480-A1A6 engines, 30 built.
- Model J50
Supercharged version of the D50E with 340 hp (250 kW) IGSO-480-A1B6 engines and increased take-off weight, 27 built.
- Excalibur 800
A modification designed originally by Swearingen Aircraft and taken over by the Excalibur Aviation Company which re-engines the Twin Bonanza with two 400hp (298kW) Avco Lycoming IO-720-A1A flat-eight engines in a new cowling and revised exhaust system. Other optional improvements were also available.
- L-23 Seminole
Chilean Air Force (C50)
Colombian Air Force (D50)
Swiss Air Force (E50)
Uruguayan Air Force
Crew: 1-2 pilots
Capacity: 5 passengers
Length: 31 ft 6 in (9.61 m)
Wingspan: 45 ft 3 in (13.78 m)
Height: 11 ft 6 in (3.51 m)
Wing area: 277 ft² (25.7 m²)
Empty weight: 5,010 lb (2,270 kg)
Max. takeoff weight: 7300 lbs (3311 kg)
Powerplant: 2 × Lycoming GSO-480-B1B6, 340 hp (253 kW) each
Maximum speed: 229 mph (199 knots, 366 km/h)
Range: 1,000 mi (870 nm, 1,600 km)
Service ceiling: 30,000 ft (9144 m)
Rate of climb: 1,614 ft/min (8.2 m/s)