Rolls-Royce Merlin prey, Rolls-Royce named the engine the "Merlin" after a small, Northern Hemisphere falcon ("Falco columbarius"). Two more Rolls-Royce engines developed just prior to the war were added to the company's range. The Rolls-Royce Peregrine was an updated, supercharged development of their V-12 Kestrel design, while the 42-litre (2,560 cu in) Rolls-Royce Vulture used four Kestrel-sized cylinder blocks fitted to a single crankcase and driving a common crankshaft, forming an X-24 layout. This was to be used in larger aircraft such as the Avro Manchester. Although the Peregrine appeared to be a satisfactory design, it was never allowed to mature since
General Electric/Rolls-Royce F136 program. This marked the first complete engine assembled following US Government validation of the F136 design in 2008. The milestone was achieved one month ahead of schedule. Citing the Weapon Systems Acquisition Reform Act of 2009, the GE Rolls-Royce Fighter Engine Team submitted an unsolicited fixed-price offer for the F136 to the Pentagon on 28 September 2009. The fixed-price approach would cover initial F136 engine production, beginning with the F136 second production lot. According to the GE Rolls-Royce Fighter Engine Team, the proposal would shift significant cost risk from taxpayers to the Fighter Engine Team until head-to-head competition begins between