Mathematician. Died aged 77.

New Zealander David Allan Spence, who has died in England, had a distinguished career applying his mathematics skills to studying various practical phenomena.

He worked particularly on aeronautical problems, having joined the scientific staff at the world-respected Royal Aircraft Establishment at Farnborough in 1952.

According to the Times newspaper, Spence worked especially on the "jet flap", used to eject a thin jet of air at the trailing edge of aircraft wings. This enables the performance to be enhanced by increasing the lift of the wing and decreasing drag.

He also worked on the propagation of shock waves and how these waves are weakened by viscosity, questions beyond the ken of most people but of great importance to supersonic flight.

David Spence was born in Auckland and educated at King's College and the University of New Zealand (at Auckland), graduating BSc and MSc, before taking a doctorate in engineering at Clare College in Cambridge.

In 1964 he moved to the engineering department at Oxford, becoming a Fellow of Lincoln. About 20 years later he was appointed a professor of mathematics at Imperial College London.

A friend, eminent New Zealand judge Lord Cooke of Thorndon, described Spence as perceptive and analytical of human motivation to an extent bordering on cynicism.

While deeply respectful of significant achievement in any walk of life he nevertheless had an "attitude towards authority markedly less than reverential - which may at times have hindered his career".

David Spence is survived by his wife, Isobel, and their two sons and two daughters.