 When the original engines were not available, the 300 hp (220 kW) Siddeley Puma engine was substituted on the second prototype in November 1918, this acquiring a new designation, the Avro 533A Manchester Mk II, and first flying in December that year.An American 400 hp (300 kW) Liberty engine was also proposed as an alternate engine.The Avro 533A Manchester Mk II flew for the first time in December 1918 with flight testing continuing with No.