Charlie Ellington (1952-2019) – a career in animal flight mechanics

Abstract

Charles Porter Ellington was born on December 31st 1952 in the State of Maryland, grew up there and in the State of Georgia, and gained his first degree at Duke University, North Carolina, all in the USA. Under the leadership of Steven Vogel and Stephen Wainwright, Duke at that time was the hub of biomechanics in the USA, and several of Charlie’s near contemporaries went on to establish influential laboratories on other US campuses. He took a different route, coming to Cambridge in 1972 on a prestigious Churchill Scholarship to work for a PhD under the supervision of Torkel Weis-Fogh, a brilliant Dane who was then the world leader in insect flight research. Weis-Fogh had recently broken new ground in aerodynamics. Using high-speed cinematography of the tiny wasp Encarsia formosa in free flight, he had described the first non-steady state mechanism for generating high lift by flapping wings. Charlie’s remit was to develop and extend this approach to other insect groups and to work towards a greater understanding of the aerodynamics of hovering flight. Disaster struck soon after, when Weis-Fogh took his own life. Charlie’s supervision was taken over by Ken Machin, a radio-astronomer turned zoologist whose outstanding experimental flair lay behind much important research in Cambridge at that time. The result was a PhD thesis that must rank among the most remarkable in the history of the degree, and spectacularly demonstrated what the disciplinary breadth of the American undergraduate system could achieve in an outstanding student. Building his own digitiser and using a computer the size of a wardrobe Charlie developed the first methodology and software for kinematic analysis of unimpeded flapping flight, and applied them to his own high-speed films of a range of hovering insects. He identified five new unsteady mechanisms for lift generation, and, crucially, was the first person to develop a vortex theory for flapping flight. He developed and extended the use of morphometric parameters in calculating aerodynamic and inertial forces and power requirements of flight. The work was published virtually intact in 1984 in a seminal series of six papers in Philosophical Transactions of the Royal Society B, and established the platform on which virtually all subsequent research on insect flight mechanics has been built. Now on the staff at Cambridge, Charlie replaced Weis-Fogh as the recognised world leader in insect flight mechanics. An excellent theoretician as well as a first-rate experimentalist, he began a programme of research and publications with a succession of postgraduates and post-doctoral assistants, primarily addressing the nature and relative importance of unsteady mechanisms in