The Cessna 421 was first produced in May 1967, the 1968 model year. It had "Stabila-Tip" fuel tanks on the wingtips (like the Cessna 310). Its electro-mechanical landing gear are similar to that of the 310. It was an immediate hit, selling 200 planes in its first year. The very next year, 1969, the design was refined, with a three-inch stretch of the fuselage, five more gallons of fuel capacity, and a 40-pound increase in gross weight. The plane was redesignated the Cessna 421A. In 1971 the design was again improved. Both empty and gross weight increased, the wingspan was increased by two feet, raising the service ceiling by 5,000 feet. The nose was stretched two feet to accommodate a larger nose baggage section. This new plane is designated the Cessna 421B. In 1975 the plane was offered with a package of equipment enabling flight into known icing conditions. In 1976 the 421C appeared which featured wet wings, the absence of wingtip fuel tanks and landing gear that was changed from straight-leg to a trailing-link design from the 1981 model year onwards. Production ended in 1985 after 1,901 aircraft had been delivered. The 421 was first certified on 1 May 1967 and shares a common type certificate with models 401, 402, 411, 414 and 425. Some 421s have been modified to accept turboprop engines, making them very similar to the Cessna 425, which itself is a turboprop development of the 421. The 421 is an all-metal low-wing cabin monoplane with a retractable tricycle landing gear, and powered by two geared[a] Continental GTSIO-520-D engines, wing-mounted in tractor configuration. The cabin is accessed from a door, on the left hand side behind the wing, and has seating for six on the basic 421, or up to ten on later variants. For details of the variants, click here. Specifications below ae for the 421C model.