Correct answer is... 280 km/h. It is equal to 151 kn or 174 mph. It is lower value then max speed of other aircrafts of a similar size. Average is about 290 km/h (157 kn or 180 mph).
The maximum speed most frequently is a term for so-called never exceed speed. Above this speed, the Curtiss YA-10 Shrike can suffer considerable damage. There are also three other types of speed that can be called "maximum speed": Vno (normal operation speed) is the maximum allowable speed of normal operation, Vb (design speed for maximum gust intensity) is the maximum speed in rough air, and Va (design maneuvering speed) is the maximum speed at which the rudders can be maximally deflected.
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