A testbed aircraft is an aeroplane, helicopter or other kind of aircraft intended for flight research or testing the aircraft concepts or on-board equipment. These could be specially designed or modified from serial production aircraft.[1][2]
^Свищёв, Георгий, ed. (1994). Авиация : Энциклопедия [Aviation : Encyclopedia] (in Russian). Москва: Большая российская энциклопедия : TsAGI. p. 735.