What Engineers Know and How They Know It
Encyclopedia
What Engineers Know and How they Know It: Analytical Studies from Aeronautical History (The Johns Hopkins University Press, 1990) (ISBN:0-8018-4588-2) is a historical reflection on engineering
practice in US aeronautics
from 1908-1953 written by an accomplished practitioner and instructor. This period represents the dawn of aviation which was fraught with uncertainties and numerous paths to many possible worlds
. The book captures two main conclusions from this period. The first order conclusion of this book is about "what engineers know." Five case studies from the history of aeronautical engineering are used to argue engineering often demands its own scientific discoveries. Thus, engineering should be understood as a knowledge-generating activity that includes applied science
but is not limited to applied science. The second order conclusion of this book pertains to "how engineers know" by using the same case studies to reveal patterns in the nature of all engineering. These patterns form an “epistemology” of engineering that may point the way to an “engineering method” as something distinct from scientific method
. Walter Vincenti ends the work with a general "variation-selection model" for understanding the direction of technological innovation in human history. The book is filled with numerous additional observations and stories told by a practitioner and instructor. This may be why Dr. Michael A. Jackson
, author of Structured Design and Problem Frames, once concluded a keynote address to engineers with the statement, "Read Vincenti's book. Read it carefully. Read it one hundred times."
. In 1987 he was inducted into the National Academy of Engineering
, “for pioneering contributions to supersonic aircraft aerodynamics and to fundamental understanding of the physical gas dynamics
of hypersonic flow.” His important textbook from the first part of his career is, Introduction to Physical Gas Dynamics (1ed ed 1965, 2nd ed 1975). Vincenti in effect had two whole careers: one as a cutting-edge aeronautical engineer and another as a leading historian of technology. This gave him a dual vantage point to think about how technological innovation works. Further, he broadened the relevance of engineering to society by co-founding a Stanford discipline called Values, Technology and Society in 1971—now called Science, Technology and Society. At the age of 90 he published his most recent work with William M. Newman, "On an Engineering Use of Engineering History" which appears in Technology and Culture
.
, the history of technology, and instructing. The five case studies used for evidence in this book come from the first half of the 20th century, 1908-1953. During this period the author worked at the National Advisory Committee for Aeronautics
(NACA) from 1940-1957. Four of the five case studies used as evidence in this book were first published independently in Technology and Culture
between 1979-1986. During this era, other authors were beginning to refute the view of engineering as only applied science. Then in 1990, Vincenti's five case studies indirectly supported this newer discourse about engineering as a knowledge-generating discipline.
, construction/production and operation. These cases come largely from the design phase of engineering. One exception is the fifth case study on flush-riveted joints which involved an intimate interplay between design and production. Second, design can be categorized as normal or radical. These case studies pertain to normal design. Third, normal design itself is multi-leveled. These levels proceed from project definition down to overall design, major component design, subdivision of component design, and highly specific problems (like planform, airfoil and high-lift devices). These five case studies come mostly from these lower levels. Thus when combined, the scope of these case studies is design, normal design and highly specific problems at the lowest level, "to help redress the neglect of this large and essential area."
design generally. The early work of Davis illustrates how useful engineering has been done by people who have no formal training in engineering. The Davis wing
was instrumental even though Davis did not have the theoretical basis to know how or why. Chapter 3 is about how engineers design in accord with flying qualities satisfactory to pilots. This case study illustrates there can be a key relationship between human behavior and engineering requirements that can greatly affect the outcomes. As such, "artifactual design is a social activity." Chapter 4 instructs the importance of control-volume
analysis situations in mechanical design. Control volume analysis was missing in physics textbooks at the time. Thus, engineers had a scientific requirement that was not addressed adequately by any natural science
. Importantly, such case studies are examples of why there is such a thing as "engineering science". Chapter 5 regards the dynamic problem of propeller
design and selection. The propeller case study illustrates how engineers develop methods to account for the absence of required scientific theory. In this case "parameter variation" was used to map-out and survey a subject where no comprehensive scientific theory (in physics) existed. Finally, chapter 6 describes the problem of designing flush-riveted joints for aircraft. This case study conveys how requirements of production can have a reverse influence on design thus driving iterations between production and design. This case study also illustrates how there are aspects of engineering that cannot adequately be described as science such as the "feel" rivet mechanics developed for how much pressure to apply when completing the aircraft's aluminum stressed-skin structure (see "tacit knowledge" discussion below).
that they may point the way for further research. He wrote, "in the final paragraph of chapter 5, I also raised the question of whether it might be profitable to look for "engineering method" analogous to but distinguishable from scientific method that has been a fruitful concern for the history of science. Could it be that the variation-selection process outlined here is that method, with its distinctive features lying in the criterion of selection and the vicarious methods used to shortcut direct trial?"
The boldface from the original text isolates the steps in a subject-neutral manner.
These six categories of engineering knowledge are:
These seven Knowledge-Generating Activities include:
, prescriptive knowledge and tacit knowledge
. He adds Gilbert Ryle's terms "knowing that" and "knowing how" to illustrate the aim of each knowledge category. "Knowing what or that" to do in engineering is a mixture of descriptive and prescriptive knowledge. "Knowing how" to do it is a mixture of prescriptive and tacit knowledge. Thus, these case studies show the need for all three kinds of knowledge in engineering.
Engineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...
practice in US aeronautics
Aeronautics
Aeronautics is the science involved with the study, design, and manufacturing of airflight-capable machines, or the techniques of operating aircraft and rocketry within the atmosphere...
from 1908-1953 written by an accomplished practitioner and instructor. This period represents the dawn of aviation which was fraught with uncertainties and numerous paths to many possible worlds
Possible Worlds
Possible Worlds may refer to:* Possible worlds, a concept in philosophy* Possible Worlds , by John Mighton** Possible Worlds , by Robert Lepage, based on the Mighton play* Possible Worlds , by Peter Porter...
. The book captures two main conclusions from this period. The first order conclusion of this book is about "what engineers know." Five case studies from the history of aeronautical engineering are used to argue engineering often demands its own scientific discoveries. Thus, engineering should be understood as a knowledge-generating activity that includes applied science
Applied science
Applied science is the application of scientific knowledge transferred into a physical environment. Examples include testing a theoretical model through the use of formal science or solving a practical problem through the use of natural science....
but is not limited to applied science. The second order conclusion of this book pertains to "how engineers know" by using the same case studies to reveal patterns in the nature of all engineering. These patterns form an “epistemology” of engineering that may point the way to an “engineering method” as something distinct from scientific method
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...
. Walter Vincenti ends the work with a general "variation-selection model" for understanding the direction of technological innovation in human history. The book is filled with numerous additional observations and stories told by a practitioner and instructor. This may be why Dr. Michael A. Jackson
Michael A. Jackson
Michael Anthony Jackson is a British computer scientist, and independent computing consultant in London, England. He is also part-time researcher at AT&T Research, Florham Park, NJ, U.S., and visiting research professor at the Open University in the UK.- Biography :Jackson was educated at Harrow...
, author of Structured Design and Problem Frames, once concluded a keynote address to engineers with the statement, "Read Vincenti's book. Read it carefully. Read it one hundred times."
Author
Walter G. Vincenti (commonly pronounced "vin-sen-tee" in the US or "vin-chen-tee" in Italian) (1917-present) is a Professor Emeritus of Aeronautical and Aerospace Engineering at Stanford UniversityStanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
. In 1987 he was inducted into the National Academy of Engineering
National Academy of Engineering
The National Academy of Engineering is a government-created non-profit institution in the United States, that was founded in 1964 under the same congressional act that led to the founding of the National Academy of Sciences...
, “for pioneering contributions to supersonic aircraft aerodynamics and to fundamental understanding of the physical gas dynamics
Gas dynamics
Gas dynamics is a branch of fluid dynamics concerned with studying the motion of gases and its consequent effects. Gas dynamics combines the principles of fluid mechanics and thermodynamics...
of hypersonic flow.” His important textbook from the first part of his career is, Introduction to Physical Gas Dynamics (1ed ed 1965, 2nd ed 1975). Vincenti in effect had two whole careers: one as a cutting-edge aeronautical engineer and another as a leading historian of technology. This gave him a dual vantage point to think about how technological innovation works. Further, he broadened the relevance of engineering to society by co-founding a Stanford discipline called Values, Technology and Society in 1971—now called Science, Technology and Society. At the age of 90 he published his most recent work with William M. Newman, "On an Engineering Use of Engineering History" which appears in Technology and Culture
Technology and Culture
Technology and Culture is a quarterly academic journal founded in 1959. It is an official publication of the Society for the History of Technology, whose members routinely refer to it as "T&C." Besides scholarly articles, the journal publishes reviews of books and museum exhibitions. Occasionally,...
.
Background
What Engineers Know was first published in 1990 when Mr. Vincenti was 73 years old after full careers in aerospace engineeringAerospace engineering
Aerospace engineering is the primary branch of engineering concerned with the design, construction and science of aircraft and spacecraft. It is divided into two major and overlapping branches: aeronautical engineering and astronautical engineering...
, the history of technology, and instructing. The five case studies used for evidence in this book come from the first half of the 20th century, 1908-1953. During this period the author worked at the National Advisory Committee for Aeronautics
National Advisory Committee for Aeronautics
The National Advisory Committee for Aeronautics was a U.S. federal agency founded on March 3, 1915 to undertake, promote, and institutionalize aeronautical research. On October 1, 1958 the agency was dissolved, and its assets and personnel transferred to the newly created National Aeronautics and...
(NACA) from 1940-1957. Four of the five case studies used as evidence in this book were first published independently in Technology and Culture
Technology and Culture
Technology and Culture is a quarterly academic journal founded in 1959. It is an official publication of the Society for the History of Technology, whose members routinely refer to it as "T&C." Besides scholarly articles, the journal publishes reviews of books and museum exhibitions. Occasionally,...
between 1979-1986. During this era, other authors were beginning to refute the view of engineering as only applied science. Then in 1990, Vincenti's five case studies indirectly supported this newer discourse about engineering as a knowledge-generating discipline.
Scope
The profession of "engineering" encompasses a wide scope of practice. Thus, the author narrows the scope of his five case studies in three ways. First, viewed end-to-end, the engineering process contains three phases including designDesign
Design as a noun informally refers to a plan or convention for the construction of an object or a system while “to design” refers to making this plan...
, construction/production and operation. These cases come largely from the design phase of engineering. One exception is the fifth case study on flush-riveted joints which involved an intimate interplay between design and production. Second, design can be categorized as normal or radical. These case studies pertain to normal design. Third, normal design itself is multi-leveled. These levels proceed from project definition down to overall design, major component design, subdivision of component design, and highly specific problems (like planform, airfoil and high-lift devices). These five case studies come mostly from these lower levels. Thus when combined, the scope of these case studies is design, normal design and highly specific problems at the lowest level, "to help redress the neglect of this large and essential area."
Case Study Summary
The five case studies are organized by chapter. Chapter 2 regards airfoilAirfoil
An airfoil or aerofoil is the shape of a wing or blade or sail as seen in cross-section....
design generally. The early work of Davis illustrates how useful engineering has been done by people who have no formal training in engineering. The Davis wing
Davis wing
The Davis wing is an aircraft wing planform that was used for some time on a variety of World War II aircraft, most notably a number of designs from Consolidated Aircraft, including the Consolidated B-24 Liberator. Use of the Davis wing ended almost immediately after the end of the war, yet it...
was instrumental even though Davis did not have the theoretical basis to know how or why. Chapter 3 is about how engineers design in accord with flying qualities satisfactory to pilots. This case study illustrates there can be a key relationship between human behavior and engineering requirements that can greatly affect the outcomes. As such, "artifactual design is a social activity." Chapter 4 instructs the importance of control-volume
Control volume
In fluid mechanics and thermodynamics, a control volume is a mathematical abstraction employed in the process of creating mathematical models of physical processes. In an inertial frame of reference, it is a volume fixed in space or moving with constant velocity through which the fluid flows...
analysis situations in mechanical design. Control volume analysis was missing in physics textbooks at the time. Thus, engineers had a scientific requirement that was not addressed adequately by any natural science
Natural science
The natural sciences are branches of science that seek to elucidate the rules that govern the natural world by using empirical and scientific methods...
. Importantly, such case studies are examples of why there is such a thing as "engineering science". Chapter 5 regards the dynamic problem of propeller
Propeller
A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...
design and selection. The propeller case study illustrates how engineers develop methods to account for the absence of required scientific theory. In this case "parameter variation" was used to map-out and survey a subject where no comprehensive scientific theory (in physics) existed. Finally, chapter 6 describes the problem of designing flush-riveted joints for aircraft. This case study conveys how requirements of production can have a reverse influence on design thus driving iterations between production and design. This case study also illustrates how there are aspects of engineering that cannot adequately be described as science such as the "feel" rivet mechanics developed for how much pressure to apply when completing the aircraft's aluminum stressed-skin structure (see "tacit knowledge" discussion below).
An Epistemology of Engineering (How Engineers Know)
Throughout the book, Walter Vincenti makes epistemology observations pertaining to engineering. The following are six of several observations made throughout the book. These observations do not constitute an "engineering method" per se but he offers a conjectureConjecture
A conjecture is a proposition that is unproven but is thought to be true and has not been disproven. Karl Popper pioneered the use of the term "conjecture" in scientific philosophy. Conjecture is contrasted by hypothesis , which is a testable statement based on accepted grounds...
that they may point the way for further research. He wrote, "in the final paragraph of chapter 5, I also raised the question of whether it might be profitable to look for "engineering method" analogous to but distinguishable from scientific method that has been a fruitful concern for the history of science. Could it be that the variation-selection process outlined here is that method, with its distinctive features lying in the criterion of selection and the vicarious methods used to shortcut direct trial?"
Seven Interactive Elements of Engineering Learning
First, there is a pattern to the iterative engineering discovery process seen in the development of flying-quality specifications. This process is referred to as "Seven Interactive Elements of Engineering Learning" and includes:- Familiarization with vehicle and recognition of problem.
- Identification of basic variables and derivation of analytical concepts and criteria.
- Development of instruments/piloting techniques for in-flight measurements.
- Growth and refinement of pilot opinion regarding desirable flying qualities.
- Combine results from 2-4 into a deliberate scheme for flying-quality research.
- Measurement of relevant flight characteristics for a cross section of aircraft.
- Assessment of results and data on flight characteristics in light of pilot opinion to arrive at general specifications.
The boldface from the original text isolates the steps in a subject-neutral manner.
Six Categories of Engineering Knowledge
Second, there is a pattern in the very categories of knowledge in engineering.These six categories of engineering knowledge are:
- Fundamental design concepts
- Criteria and specifications
- Theoretical tools
- Quantitative data
- Practical considerations
- Design instrumentalities
Seven Knowledge-Generating Activities
Third, Walter Vincenti sees a pattern in knowledge/science generating activities of engineering.These seven Knowledge-Generating Activities include:
- Transfer from science
- Invention
- Theoretical engineering research
- Experimental engineering research
- Design practice
- Production
- Direct Trial
Relationship Between Categories and Activities
Fourth, by placing six categories of knowledge and the seven knowledge-generating activities on an x-y table, these knowledge generating activities cut across the categories of knowledge in a partially predictable way. The resulting table serves as an approximation for what engineering tasks may be likely to produce new engineering knowledge. The resulting diagram "is intended for discussion more than a set of hard and fast divisions."Engineering Knowledge Classification
Fifth, he re-classifies engineering knowledge itself. Knowledge generated by engineering may normally be categorized by phases such as design, production or operations. Another way to think about engineering knowledge categories is descriptive knowledgeDescriptive knowledge
Descriptive knowledge, also declarative knowledge or propositional knowledge, is the species of knowledge that is, by its very nature, expressed in declarative sentences or indicative propositions...
, prescriptive knowledge and tacit knowledge
Tacit knowledge
Tacit knowledge is knowledge that is difficult to transfer to another person by means of writing it down or verbalising it. For example, stating to someone that London is in the United Kingdom is a piece of explicit knowledge that can be written down, transmitted, and understood by a recipient...
. He adds Gilbert Ryle's terms "knowing that" and "knowing how" to illustrate the aim of each knowledge category. "Knowing what or that" to do in engineering is a mixture of descriptive and prescriptive knowledge. "Knowing how" to do it is a mixture of prescriptive and tacit knowledge. Thus, these case studies show the need for all three kinds of knowledge in engineering.
Variation-Selection Model of Technological Innovation
Finally, he posits a variation-selection model for knowledge growth. At all levels of design hierarchy, growth of knowledge acts to increase the complexity and power of the variation-selection process by modifying both the mechanism for variation and expanding the processes of selection vicariously. Variation and selection each add two realistic principles for the advancement of technology: blindness to variation and unsureness of selection. Blindness and unsureness characterize the difficult or arduous nature of technology evolution in the variation-selction model. The author then reviews the five case studies retrospectively to demonstrate how variation-selection and blindness-unsureness were at work in each case. In total, "the cumulative growth of engineering knowledge as the result of individual variation-selection processes acts to change the nature of how those processes are carried out."See also
- EngineeringEngineeringEngineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...
- Airfoils
- Davis wingDavis wingThe Davis wing is an aircraft wing planform that was used for some time on a variety of World War II aircraft, most notably a number of designs from Consolidated Aircraft, including the Consolidated B-24 Liberator. Use of the Davis wing ended almost immediately after the end of the war, yet it...
- Control volumeControl volumeIn fluid mechanics and thermodynamics, a control volume is a mathematical abstraction employed in the process of creating mathematical models of physical processes. In an inertial frame of reference, it is a volume fixed in space or moving with constant velocity through which the fluid flows...
- PropellersPropellerA propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...
- Flush rivets