Armstrong Siddeley Motors memo from Mr Lindsay to Mr Finch: re. the short Life Viper...

1. The Short Life Viper was designed for a flying life of 10 hours but it became clear during its development life that it should be capable of running longer than this and we suggested that 25 hours would be reasonable. 2. During the short running and flying in the Jindivik it was found, contrary to our original understanding, that the engine would have to spend some considerable time in the speed range 6500 to 8500 rpm. The compressor blades in the Short Life Viper suffer severely from vibration in this speed range and under these conditions are known to have a short and somewhat indeterminate life. In the last paragraph Mr Lindsey says that compressor failure is always a possibility at the above mentioned speeds