The Cessna 210 Centurion is a 6 seat, high-performance, retractable-gear single-engine general aviation aircraft which was first flown in January 1957. Production was completed in 1985 In 1967 the model 210G introduced a cantilever wing replacing the strut-braced wing. Its planform changed to a constant taper from root chord to tip chord. In 1970 the 210K became the first full 6-seat model; this was achieved by replacing the flat-leaf main gear springs with tapered tubular steel springs of greater tread width (which allowed the tires to be nested farther back in the fuselage). In 1979 the 210N model eliminated the folding doors which previously covered the retracted main gears; the retracted tubular springs lie in shallow channels along the bottom of the fuselage and the wheels fit snugly into a closed depression on the fuselage bottom. Other developments included long side windows on the 210K's larger cabin, widely spaced nose landing lights on the 210L. Aerospace Systems and Technologies offers an ice protection system for the Cessna 210, models L, M and N. This system is a TKS technology that "weeps" chemicals which depress the freezing point of water and will both remove accumulated ice and then prevent ice formation.