Yakovlev Yak-40 Yak-40K

On Soviet local routes the Yak-40 replaced aeroplanes that had always carried people and freight interchangeably. The passenger version, with its ventral airstairs and narrow doors, could not do that job: loading a spare engine or a pallet of parts through the forward door was simply impossible. The answer arrived in 1975 as the Yak-40K, with a cargo door in the fuselage side wide enough to accept palletised loads.

The cabin is handled in modules: seats on rails that come out quickly, and a floor able to take concentrated loads. The changeover can be done at an ordinary field in a short time, so an aircraft can fly passengers in the morning and freight in the afternoon. All-cargo payload rises to 3,200 kg; the documented combi splits run from ten passengers with rather more than two tonnes of freight to eighteen passengers with a little over one.

The Yak-40K was produced next to the passenger versions from 1975 until the Saratov line closed in 1981. Spanish-language sources tie it to the fourth production series, the one that also brought the higher payload and the two-class interior, which makes the freighter less a separate derivative than the fullest expression of that last step in the type's evolution.

Cargo work kept the type earning long after passenger operations had stopped paying. In the late-2010s surveys several of the handful of active Yak-40s in Kazakhstan and the Russian Far East were in freight configuration, serving destinations with almost no infrastructure where no other jet could land.