The Beechcraft Model 18, or "Twin Beech", as it was better known, is a 6-11 place, twin-engine, low-wing, conventional-gear aircraft that was manufactured by the Beech Aircraft Corporation of Wichita, Kansas. This model saw service during and after World War II in a number of versions including the United States Army Air Forces C-45 Expeditor, AT-7 Navigator, AT-11 Kansan, and for the United States Navy, UC-45J Navigator and the SNB-1 Kansan. An estimated aggregate total time in service for the aircraft time is in excess of 20,000,000 hours of flight time.
The Beech 18 is the most modified US-certified aircraft design, with over 200 FAA approved Supplemental Type Certificates on record for the aircraft.
The aircraft uses have included aerial spraying, sterile bug release, fish seeding, dry ice cloud seeding, aerial fire fighting, airborne mail pick up and drop, ambulance service, numerous movie productions, skydiving, freight, gun and drug smuggling, engine test bed, skywriting and banner tow. A number of Model 18s were operated as passenger aircraft, The Model 18 was also the first aircraft flown by Philippine Airlines, Asia's first and oldest airline. Many are now in private hands as highly prized collectibles.
Design and development
By the late 1930s, the winds of war had blown across Europe. Beechcraft management knew the company would be called upon to help the allied cause and they bet the future on increased production facilities and a new design dubbed the Model 18. The design was mainly conventional for the time, including twin radial engines, all-metal semi-monocoque construction with fabric covered control surfaces and "taildragger" undercarriage, while less common were the twin tail fins. Early production aircraft were either powered by two 300 hp (225 kW) Jacobs L6s or 260kW (350hp) Wright R-760Es. The 450 hp (295 kW) Pratt & Whitney Wasp Junior became the definitive engine from the prewar C18S onwards. The Beech 18 prototype first flew on 15 January 1937.
The aircraft has used a variety of engines and has had a number of airframe modifications to increase gross weight and speed. At least one aircraft was modified to a 450kW (600hp) Pratt & Whitney R-1340 powerplant configuration. With the added weight of approximately 200 pounds per engine, the concept of a Model 18 fitted with R-1340 engines was deemed unsatisfactory due to the weakest structural area of the aircraft being the engine mounts. With the exception of the center truss, the central component around which the entire aircraft is built, nearly every airframe component has been modified at one time or another.
Construction of the Beechcraft Model 18 ended in 1970 with the last Model 18 built going to Japan Airlines. Beechcraft set a record that still stands today for longest continuous production of a piston engine aircraft. Through the years, 32 variations of the basic design had flown, over 200 improvement modification kits were developed, and almost 8,000 aircraft had been built. Some aircraft were almost unrecognizable as having originated as a Beech 18. In one case the aircraft was modified to a triple tail, tri-gear, hump backed configuration and appeared similar to a miniature Lockheed Constellation.
Operational history
China sent the company 750k USD in return for light bombers based on the Model 18 design, but by the beginning of the war, only 39 Model 18s had been sold. Work began in earnest on a variant specifically for training fledgling military pilots, bombardiers and navigators. The effort resulted in the Army AT-7 and Navy SNB. Further development led to the AT-11 and SNB-2 navigation trainers and the C-45 military transport. There was even, eventually, an experimental XA-38 attack version with a huge cannon in the nose, although it never went into production. The USAF Strategic Air Command had Beechcraft Model 18 (AT-11 Kansans, C-45 Expeditors, F-2 Expeditors, the "F" standing for "Fotorecon", and UC-45 Expeditors) from 1946 through 1951. The C-45 flew in US Air Force service until 1963, the US Navy retired their last SNB in 1972 while the US Army flew their C-45s through 1976.
Some of the modifications created by independent engineering entrepreneurs were adopted in concept by the factory in later production versions in similar fashion to the current practice Harley Davidson copying of custom motorcycles built in the 1960s and 1970s. Among the most notable cooling air and exhaust modifications were those engineered by Benjamin Israel while employed by Conrad Conversions. His modifications were based largely on creating a more efficient use of cooling air to reduce cooling drag, a major detriment to aircraft cruise performance. The difference in cruise performance was a significant 10% or better at the same power settings as before the modifications. These modifications were largely copied on the factory produced G and H models.
A factory option at one point was the addition of JATO bottles on each engine nacelle which added the equivalent of 200 horsepower per engine for about 12 seconds. The most successful powerplant upgrade was that of the Pratt & Whitney PT-6 turbine engine and Hartzell propellor. This combination of engine and propellor successfully extended the commercial life of the aging aircraft.
Survivors
Below is a list of museums or sites which have a Beechcraft Model 18 on display:
- Alberta Aviation Museum
- Castle Air Museum
- Museum of Transport and Technology
- Western Canada Aviation Museum
Operators
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Argentina
- Bolivia
- Brazil
- Canada
- China
- Colombia
- Costa Rica
- Côte d'Ivoire
- Dominican Republic
- Ecuador
- El Salvador
- France
- Guatemala
- Honduras
- Indonesia
- Italy
- Mexico
- Nicaragua
- Niger
- Nigeria
- Peru
- Philippines
- Portugal
- Somalia
- South Africa
- Spain
- Sri Lanka
- Sweden
- Thailand
- Turkey
- United Kingdom: Royal Air Force, Royal Navy
- United States: US Army, US Army Air Corps, US Army Air Force, US Air Force, US Marine Corps, US Navy
- Uruguay
- Venezuela
- Zaire
Specifications (UC-45 Expeditor)
General characteristics
- Crew: 2 pilots
- Capacity: 6 passengers
- Length: 34 ft 2 in (10.41 m)
- Wingspan: 47 ft 8 in (14.53 m)
- Height: 9 ft 8 in (2.95 m)
- Wing area: 349 ft² (32.4 m²)
- Empty weight: 6,175 lb (2,800 kg)
- Loaded weight: 7,500 lb (3,400 kg)
- Max takeoff weight: 8,727 lb (3,959 kg)
- Powerplant: 2× Pratt & Whitney R-985-AN-1 "Wasp Junior" radial engines, 450 hp (336 kW) each
Performance
- Maximum speed: 225 mph (195 knots, 360 km/h)
- Range: 1,200 mi (1,000 NM, 1,900 km) at 160 mph (260 km/h)
- Service ceiling: 26,000 ft (7,930 m)
- Rate of climb: 1,850 ft/min (9.4 m/s) |
