“When you promote a good engineer to manager, you may get a bad manager and lose a good engineer” is a popular saying of unknown authorship. “One loses a good contributor and gets a bad manager, usually with a nervous breakdown. A good engineer is not necessarily a good manager of an engineering department” was cited in a 1955 book. “Why ruin a good engineer to make a bad manager?” was cited in a 1972 book, and there was a speculation that the saying went back to the depression of the 1930s, when many people were out of work and engineers were easy to hire. “When I promoted one of my engineers to a management position, I not only got a bad manager, I lost a good engineer” was cited in a 1990 book.
 
“Very much a cliché – promoting a good engineer to a manger [sic] means losing a good engineer and gaining a bad manager” was cited in a 2008 article.
 
     
Google Books
What Makes an Executive?:
Report of a Round Table on Executive Potential and Performance
By Round Table on Executive Potential and Performance
New York, NY: Columbia University Press
1955
Pg. 118:
A participant remarked that it is a common mistake in business to take “an outstanding contributor and make a manager out of him. One loses a good contributor and gets a bad manager, usually with a nervous breakdown. A good engineer is not necessarily a good manager of an engineering department. The sources of satisfaction are not the same.”
 
Google Books
Personnel
Volume 49
1972
Pg. 53:
Turning engineers into managers
Robert Caird Lewis
Why ruin a good engineer to make a bad manager? The question implies the all-too-frequent results when upper echelons decide to make the conversion. Still, they persist, perhaps because they have precedents stretching back as far as the depression of the Thirties. 
 
Google Books
The Multinational Company in Europe:
Some Key Problems
By Michael Z. Brooke and H. Lee Remmers
Ann Arbor, MI: University of Michigan Press
1974, ©1972
Pg. 117:
When he reaches management in this way, he is well acquainted with his function but does not always know how to manage it. This is why we sometimes lose a good engineer and gain a bad manager. In other instances, an old-time engineer (or old-time auditor, economist and so on) will receive management training through advanced management courses or by way of a graduate school for management, usually being sent and paid by his company for this long leave of absence.
   
Google Books
AIAA Space Programs and Technologies Conference : September 25-28, Huntsville, AL
By the American Institute of Aeronautics and Astronautics
Washington, DC: American Institute of Aeronautics and Astronautics
1990
Pg. 38:
Some said such things as “when I promoted one of my engineers to a management position, I not only got a bad manager, I lost a good engineer.”
   
Pragmatic Outsourcing
August 22, 2008
Offshore productivity: developers
(...)
Very much a cliché – promoting a good engineer to a manger means losing a good engineer and gaining a bad manager.
 
IS Survivor Publishing
Why engineers should become terrific managers, but often don’t.
The traits that make for the best engineers … the habit of success and the ability to design effective systems … could turn them into outstanding managers. Too bad the one backfires on so many engineers-turned-managers, while they ignore the other.
By Bob Lewis | August 13, 2012
“When we promoted him, we lost a good engineer and gained a bad manager.”
 
It’s a common complaint. Engineering calls for a very different set of skills, aptitudes, and character traits than management, so there’s no particular reason to expect an engineer, no matter how smart and successful, to become a good manager.
 
Twitter
Dani Fankhauser
‏@DaniFankhauser
@DavidJarrick it was solid. also my dad, aerospace engineer, used to joke “promote engineer, lose a good engineer and gain a bad manager” 😊
2:04 PM - 2 Jan 2013
 
Bangkok Post (Thailand)
Transforming a technical expert into a people’s champion
Published: 25-Dec-14
Writer: Sorayuth Vathanavisuth
(...)
There’s an old saying that when you promote a good engineer to manager, you may end up with a bad manager and lose a good engineer. The moral is to be careful when making decisions involving technical talent and people issues.