This was a MkII Lancaster built by Sir W.G. Armstrong Whitworth Aircraft Ltd., Whitley, Coventry. Part of the second production batch of 100 aircraft (LL617-LL653, LL660-LL704 and LL716-LL739) as part of contract No. 239/SAS/C4(C), all powered by Bristol Hercules XVI radial air cooled engines of 1,735 hp each. Only 300 of these aircraft were built during a temporary hiccup in Merlin engine production. Deliveries commenced October 1943; completed March 1944 (average rate of production slightly over 4 aircraft per week). 115 was one of a very few Squadrons which operated this type.
The Hercules, a double-row, fourteen-cylinder, sleeve-valve radial engine was developed in 1936. Hercules production continued through the Second World War years when it was used in the Wellington, Stirling, Halifax and Beaufighter as well as the Lancaster.
Even though the Hercules XVI engines were more powerful than the legendary Merlin power plant, they did not give the Lancaster better performance. The Hercules engines used more fuel and caused more drag thus the rate of climb, top speed and range were less then that of the Lancaster Mk. I