11th May 2022 – British ASV Bombsights 1941-1946

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Talk by Simon Watts MBE DSc FREng – British ASV Bombsights 1941-1946

During 1940 and 1941 the detection performance of ASV systems, searching for targets on the sea surface, steadily improved.  This was due to both advances in technology and improved training of ASV operators.  However, it was found that often good radar contacts failed to convert into successful attacks.  This was due to systematic errors in the final approach to the target, with insufficient allowance being made for the relative drift between aircraft and target.  This was particularly evident at night, when visual homing was not possible in the closing stages of an attack.  The introduction of the Leigh Light in 1942 greatly assisted with night attacks but often no target was found when the light was switched on, at a range of about 1 mile, due to the aircraft approaching on the wrong bearing.

The development of ranging and homing devices to enable ASV to be used throughout an attack had been started early in the war by the Air Ministry Research Establishment (AMRE).  During the course of the war a series of ASV bombsights were developed, in attempts to address this requirement.  Bombsights were also developed in the USA for use with their ASV systems and these were used by Coastal Command in some of the US aircraft supplied through the lend-lease programme.

This talk describes the various British ASV bombsights developed for RAF Coastal Command and the RN Fleet Air Arm, covering ASV bombsights Marks I to V.  Brief mention will also be made of the US systems used by Coastal Command, which had British designations of Marks VI and VII.  First, the ASV systems for which bombsights were developed will be briefly introduced.  The requirements for a bombsight will be explained and then the various systems, mainly designed at TRE, will be described.

Simon Watts was a deputy Scientific Director and Technical Fellow in Thales UK until 2013 and is a Visiting Professor in the department of Electronic and Electrical Engineering at University College London.  He received an MA in Engineering Science from the University of Oxford in 1971, an MSc in Radiocommunication and Radar Technology from the University of Birmingham in 1972 and a PhD from the CNAA in 1987.  In 2013 he was also awarded a DSc by the University of Birmingham, for research on sea clutter modelling.  He joined Thales (then EMI Electronics) in 1967 and worked on a wide range of radar and EW projects, with a particular research interest in airborne maritime radar and sea clutter.  He is author and co-author of over 80 journal and conference papers, two books on sea clutter, various book chapters on clutter and several patents.  He has also published two books on the history of airborne maritime surveillance radar.  Simon Watts was chairman of the international radar conference RADAR-97 in Edinburgh UK.  He received the IEE JJ Thomson Premium Award in 1987, the IEE Mountbatten Premium Award in 1991 and the IEEE AES Warren White Award in 2020 for “contributions to airborne maritime surveillance radar design and the modelling of radar sea clutter”. He was appointed MBE by HM the Queen in 1996 for services to the UK defence industry and is a Fellow of the Royal Academy of Engineering, Fellow of the IET, Fellow of the IMA and Fellow of the IEEE.