Antonov An-4

An-4 is the design bureau designation for the An-2ZA, a variant of the Antonov An-2 intended specially for high-altitude meteorological research. It has a glazed position immediately in front of the tail fin for an observer. The ZA suffix stands for Zondirovanie Atmosfery, translatable as 'air sampling'. The Shvetsov ASh-62 engine has a TK supercharger mounted on the starboard side of the cowling. This arrangement enables the An-4 to maintain power up to an altitude of 10,000m. The spinner of the An-2 standard model is deleted to aid engine cooling, and the original ailerons have been replaced by an unslotted variety.