Cessna 421 Cessna's first 400-series twin appeared in 1962, the 411, which not only attracted a woeful and perhaps unjustified reputation for poor single-engined handling, it also heralded the arrival Just as the big bore 520 launched Cessna’s 400 series aeroplanes, there’s growing sentiment that these big comfortable piston twins are enjoying numbered days with legislation that will see the end of Tetra-ethyl lead as a vital ingredient of amongst other fuels, 100LL Avgas.