The company went on to develop a short life engine to power unmaned target drones. This engine was called the Viper and was developed by Bristol Siddeley and subsequently, Rolls Royce. It defied its "short life" tag to sell in great numbers over many years.
Armstrong Siddeley's most powerful engine was the F9 Sapphire but this engine was developed by Metrovick and given to Armstrong Siddeley when the former company withdrew from the aircraft engine industry.
In 1959 Armstrong Siddeley merged with Bristol Aero Engines and the new company, known as Bristol Siddeley, went on to achive even greater things.
