The Avro Type 557 Ava was a British twin engined biplane torpedo bomber of the 1920s. It was developed by Avro to meet a requirement for a heavy torpedo bomber for the Royal Air Force, but was unsuccessful, only two prototypes being built.
The British Air Ministry produced a requirement in 1922 for a long ranged land based torpedo bomber. The specification required that the aircraft be capable of carrying a 21 inch torpedo or an equivalent weight of bombs, and produced responses both from Blackburn Aircraft (the Cubaroo) and Avro. Roy Chadwick, chief designer of Avro, initially produced a single engined design, the Avro 556 powered by a Napier Cub engine, similar to the Cubaroo. This was however rejected in favour of a twin engined aircraft using two Rolls-Royce Condor engines, this being designated the Avro Type 557 Ava, and winning an order of two prototypes from the Air Ministry. Completed in secret (owing to its armament with a 21 inch torpedo, thought able to sink the largest warships), the first prototype Ava (serial number N171) flew in mid 1924.
The Air Ministry dropped its plans to use the 21 inch torpedo, but Avro continued with construction of the second prototype, which was of all metal construction but was otherwise similar to the first prototype, flying on 22 April 1927. While a modified version of the Ava was proposed to meet a specification for a heavy bomber, it was unsuccessful and no further aircraft being built.