Flight Test: The Avro Arrow and a Career in Aeronautical Engineering

Inner Scale Publishing


The Inner Scale name was inspired by the Avro Arrow's combined Mach/Airspeed indicator which displayed the airspeed (in knots) on an outer scale and the Mach number (airspeed divided by the speed of sound) on an inner scale. One of the more significant documents published in the book is a graph drawn by Ralph Waechter in 1958 that shows the Arrow's Mach number as a function of time (as read from the inner scale) during the particular flight that achieved the Arrow's highest speed. The graph also shows the Arrow's altitude as a function of time, in addition to various engine parameters that were measured during the same flight. 

About the Author


David Waechter is a professional engineer who has worked in research and development for his entire career. He received B.A.Sc. and M.A.Sc. degrees from the University of Toronto and a Ph.D. from Carleton University (Ottawa), all in electrical engineering. He has worked on technologies for  aerospace, defence, energy, and medical applications. He resides in Southern Ontario.