Paper given at the 'Computers in Use' History of Computing Conference, University of Manchester, July 2006.

1. Can we have a modelling machine?
The choice between digital and analog
computer in British aeronautical research
Charles Care
“Computer in use”
Manchester
July 2006

2. Aeronautical technologies
• Aeronautics – a field of high technology
• Interesting to look at the technologies
supporting high technologies…
• In particular, the technology that
supports engineering design work

3. Computer as a modelling machine
• Computer as an information processor is an
well established ‘history’
• This research is investigating the history of
the computer as a modelling technology
• The focus is on scientists and engineers
• The computer (and associated technologies)
assists an engineer’s problem-formulating,
problem-solving activity.

4. Computer as a modelling machine
“A recent conference... attempted to
map out the history of software,
considering it as science, engineering,
labour process, reliable artefact and
industry... What the conference missed
was software as model, software as
experience, software as medium of
thought and action… It did not consider
the question of how we have put the
world into computers.”
Mahoney, M. “The histories of computing(s)”,
Interdisciplinary Science Reviews, 30(2), 2005.

5. Aeronautics, aerodynamics and
context of modelling technologies
• Trend towards general purpose and the
abstract
– Introduction of formalisms (aerodynamics)
– Also experimental formalisms as experiment
shifted from being field-based to become a
laboratory activity.
• The wind tunnel (abstraction of full-scale flow)
• The electrolytic tank (further abstraction, flow
represented with electrical fields)
• Each abstraction needs to become trusted by
engineering culture…engineering trust

6. Analog taxonomies
• Direct / indirect
– Used by contemporary writers on analog
computing (1950 – 1970)
– Shaped by usage
– Direct
• Direct mapping (analogy) between systems
• MIT Network Analyzer
– Indirect
• Relationship between two systems mediated by
mathematics… e.g. differential equations
• MIT Differential Analyzer

7. Aeronautical modelling:
the electrolytic tank
G. I. Taylor and C. F. Sharman, A Mechanical Method for
Solving Problems of Flow in Compressible Fluids. Proceedings
of the Royal Society of London,1928.

8. Post-war British aircraft design
and the application of computing
“There was a lack of design engineer because
so many were required for stress calculations
and it was hoped that better methods of
calculating would improve the position.”
Brig. Hinds, 1952
“The level of skill and initiative expected by the
firms of their [human] computers is not high. It
was suggested that the introduction of one or
two computers of higher calibre, would pay
handsome dividends…. computing activities
would be in the charge of a capable officer, who
would not only plan and lay out the work, but
would keep abreast of development in outside
centres, such as N.P.L. and R.A.E.”
Goodwin and Hollingdale, 1952

9. Post-war British aircraft design
and the application of computing
“There was a lack of design engineer because
so many were required for stress calculations
and it was hoped that better methods of
calculating would improve the position.”
Brig. Hinds, 1952
“The level of skill and initiative expected by the
firms of their [human] computers is not high. It
was suggested that the introduction of one or
two computers of higher calibre, would pay
handsome dividends…. computing activities
would be in the charge of a capable officer, who
would not only plan and lay out the work, but
would keep abreast of development in outside
centres, such as N.P.L. and R.A.E.”
Goodwin and Hollingdale, 1952

10. Post-war British aircraft design
and the application of computing
“There was a lack of design engineer because
so many were required for stress calculations
and it was hoped that better methods of
calculating would improve the position.”
Brig. Hinds, 1952
“The level of skill and initiative expected by the
firms of their [human] computers is not high. It
was suggested that the introduction of one or
two computers of higher calibre, would pay
handsome dividends…. computing activities
would be in the charge of a capable officer, who
would not only plan and lay out the work, but
would keep abreast of development in outside
centres, such as N.P.L. and R.A.E.”
Goodwin and Hollingdale, 1952

11. Post-war British aircraft design
and the application of computing
• Aeronautical Research Council (ARC)
– Established 1909, disbanded 1970
– “an ingenious mechanism… for peer review of secret work”
(Nahum, 2002)
– Establishment of a Computation Panel (which later grew into
a sub-committee) – around 10 members including:
• S. C. Redshaw (Prof. Civil engineering – Birmingham)
• M. Wilkes (Cambridge), F C Williams (Manchester)
• G. H. Hinds (Director of Weapons Research, MoS)
• E. T. Goodwin (NPL) and S. H. Hollingdale (RAE)
“…only a few people in the aircraft industry
realised the need for efficiency in computation
and many were content to take months over
work that could, and had, been done in a few
days.”

12. Post-war British aircraft design
and the application of computing
• Aeronautical Research Council (ARC)
– Established 1909, disbanded 1970
– “an ingenious mechanism… for peer review of secret work”
(Nahum, 2002)
– Establishment of a Computation Panel (which later grew into
a sub-committee) – around 10 members including:
• S. C. Redshaw (Prof. Civil engineering – Birmingham)
• M. Wilkes (Cambridge), F C Williams (Manchester)
• G. H. Hinds (Director of Weapons Research, MoS)
• E. T. Goodwin (NPL) and S. H. Hollingdale (RAE)
“…only a few people in the aircraft industry
realised the need for efficiency in computation
and many were content to take months over
work that could, and had, been done in a few
days.”

13. Deciding between analog and
digital: the case of flutter
• One of the major calculations that aircraft
designers had to make
• By 1955, it had “become an increasingly
serious problem due to the combination of
higher aircraft speeds and thinner wings and
tail surfaces”
“…calculations have to cover more degrees of
freedom, and the effects of variation in the
aerodynamic and structural parameters need to
be investigated to a greater extent… and high
speed computational aids have become a
necessary adjunct to flutter problems.”
(Templeton, 1955)

14. Deciding between analog and
digital: the case of flutter
• One of the major calculations that aircraft
designers had to make
• By 1955, it had “become an increasingly
serious problem due to the combination of
higher aircraft speeds and thinner wings and
tail surfaces”
“…calculations have to cover more degrees of
freedom, and the effects of variation in the
aerodynamic and structural parameters need to
be investigated to a greater extent… and high
speed computational aids have become a
necessary adjunct to flutter prediction.”
(Templeton, 1955)

15. Deciding between analog and
digital: the case of flutter
• Flutter simulators:
analog devices to solve
the ‘flutter equations’
– FS I, a prototype
machine with 2 degrees
of freedom
– FS II, 6 degrees of
freedom
– FS III, 12 degrees of
freedom
The RAE FS I

16. Deciding between analog and
digital: the case of flutter
The RAE FS II
Also other special purpose analog devices
to mechanise the other stages of the flutter
problem (NOMAD, INCA, MAYA)

17. Deciding between analog and
digital: the case of flutter
“...an analogue flutter simulator would be
preferred by the people working on flutter
because an all-purpose machine could be used
for other computations and therefore would not
be for exclusive use.”
Diprose, 1952
“… the popularity of analogue machines was
due to the fact that firms already employed staff
trained in electronics and servo-mechanisms
who could be used to service such machines.
Digital machines required more specialised
servicing teams and some training schemes
would be required to provide the necessary
staff.
Prof. Pugsey, 1952

18. Deciding between analog and
digital: the case of flutter
“...an analogue flutter simulator would be
preferred by the people working on flutter
because an all-purpose machine could be used
for other computations and therefore would not
be for exclusive use.”
Diprose, 1952
“… the popularity of analogue machines was
due to the fact that firms already employed staff
trained in electronics and servo-mechanisms
who could be used to service such machines.
Digital machines required more specialised
servicing teams and some training schemes
would be required to provide the necessary
staff.
Prof. Pugsey, 1952

19. Thirty year persistence, four
shortcomings of digitalisation
• Why did analog persist?
• Four major problems, three relating to programming
and one to engineering trust.
1. Engineers were not trained to program – either they
needed to learn how, or alternatively out-source to a
programmer.
2. Computing was not necessarily separable from the
design process.
3. Issue over whether the design process (and the
engineers) should be adapted to fit the technology.
Should computing be close-shop or open-shop?
1. Great engineering tradition in communicating
knowledge through physical analogies

20. Thirty year persistence, four
shortcomings of digitalisation
• Why did analog persist?
• Four major problems, three relating to programming
and one to engineering trust.
1. Engineers were not trained to program – either they
needed to learn how, or alternatively out-source to a
programmer.
2. Managing computations was not necessarily
separable from the design process.
3. Issue over whether the design process (and the
engineers) should be adapted to fit the technology.
Should computing be close-shop or open-shop?
1. Great engineering tradition in communicating
knowledge through physical analogies

21. Thirty year persistence, four
shortcomings of digitalisation
• Why did analog persist?
• Four major problems, three relating to programming
and one to engineering trust.
1. Engineers were not trained to program – either they
needed to learn how, or alternatively out-source to a
programmer.
2. Managing computations was not necessarily
separable from the design process.
3. Issue over whether the design process (and the
engineers) should be adapted to fit the technology.
Should computing be close-shop or open-shop?
1. Great engineering tradition in communicating
knowledge through physical analogies

22. Thirty year persistence…
Mr Diprose viewed with alarm the implied tendency to
build up large programmes and so have the arithmetical
processes divorced from the physical problem.
[In response] Dr Wilkes said there was less
danger of this happening with automatic
digital computers than with a team of hand
computers. The machine would employ no
short cuts or approximations which the
programmer did not put into his coding and
in general simple repetitive methods would
be used on an automatic digital computer.
The work could be carried out to any
accuracy required by coding the arithmetic
double length or even triple length.
(Minutes of the 3rd meeting of the ARC computation panel.)

23. Conclusion
• No direct barrier to digital computing
• Engineering practice adapted to fit the technology.
• Analog computing was part of their trustworthiness
and professional credibility.
• 30 year persistence corresponds to length of a
working life

24. Conclusion
• No direct barrier to digital computing
• Engineering practice adapted to fit the technology.
• Analog computing was part of their trustworthiness
and professional credibility.
• 30 year persistence corresponds to length of a
working life
Why research this, where’s it heading?
• Trying out the modelling machine theme
• Exploring the shaping of professional status and
knowledge – engineering trust
• Developing a ‘what works’, or ‘if it ain’t broke’,
historiography to study analog persistence.

25. Conclusion
• No direct barrier to digital computing
• Engineering practice adapted to fit the technology.
• Analog computing was part of their trustworthiness
and professional credibility.
• 30 year persistence corresponds to length of a
working life
Why research this, where’s it heading?
• Trying out the modelling machine theme
• Exploring the shaping of professional status and
knowledge – engineering trust
• Developing a ‘what works’, or ‘if it ain’t broke’,
historiography to study analog persistence.

26. Selected References
• Allan G. Bromley. Analog computing devices. In William Aspray, editor,
Computing before Computers, pages 159–199. Iowa State University
Press, 1990.
• Robert Bud and Philip Gummett, editors. Cold War, Hot Science:
Applied Research in Britain's Defence Laboratories 1945–1990.
Science Museum, London, 2 edition, 2002.
• Martin Campbell-Kelly and William Aspray. Computer, A History of the
Information Machine. BasicBooks, New York, 1996.
• David Edgerton. Warfare state : Britain, 1920-1970. Cambridge
University Press, 2006.
• S. H. Hollingdale and K. V. Diprose. The role of analogue computing in
the aircraft industry. Typeset report of the Computation Panel of the
ARC. Dated 7 January. National Archives: DSIR 23/21372, 1953.
• S. H. Hollingdale and G. C. Toothill. Electronic Computers. Penguin
Books, 1970. 2nd edition.
• Michael S. Mahoney. The histories of computing(s). Interdisciplinary
Science Reviews, 30(2), 2005.
• Andrew Nahum. The royal aeronautical establishment from 1945 to
concorde. In Bud and Gummett (2002).

27. Selected References (cont.)
• Edward Pyatt. The National Physical Laboratory : a history. Adam
Hilger Ltd., Bristol, 1982.
• James S. Small. The Analogue Alternative : The Electric Analogue
Computer in Britain and the USA, 1930–1975. Routledge, London,
2001.
• H. Templeton. Computational aids or the solution of flutter problems.
National Archives: DSIR 23/23788, 1955.
• Stephen Robert Twigge. The early development of guided weapons in
the United Kingdom :
• 1940-1960. Harwood Academic, 1993.
• Stephen Robert Twigge. Ground-based air defence and abm systems.
In Bud and Gummett (2002).
• Aristotle Tympas. From digital to analog and back: The ideology of
intelligent machines in the history of the electrical analyser. IEEE
Annals of the History of Computing, 18(4):42–48, 1996.
• R. Keil-Slawik U. Hashagen and A. Norberg, editors. History of
Computing: Software Issues, Berlin, 2002. Springer.
• Walter G. Vincenti. What Engineers Know and How They Know it :
analytical studies from aeronautical history. The John Hopkins
University Press, Baltimore, 1990.

28. Major sources for understanding
military science research

29. Previous work on analog
computing history