sentences:  On being given this piece of rather pointed evidence to the contrary by prominent aviation author Charles Gibbs-Smith, James Watson promptly changed his story.As with his first aeroplane, it is safe to assume that Watson's primary concern about the No.2 would have been its powerplant; above all other considerations, he had to equip it with an engine that was able to get it into the air.Quite probably, his choice of engine was driven by cost and availability.