How Technical Should an Engineering Manager Be?

David Packard (of HP fame) gave a talk on this very topic in 1960 which is still relevant today;

Speech by Dave Packard to HP Managers March 8, 1960 - https://gizmodo.com/the-hp-way-how-bill-hewlett-and-i-built-...

Relevant Excerpt:

Over the years we have developed the policy that it is important for the supervisor to thoroughly know and understand the work of his group. A debate on this has been carried on by management people for years. Some say you can be a good manager without having the slightest idea of what you are trying to manage, that the techniques of management are all important. There are many organizations which work that way. I don't argue that the job can't be done that way but I do argue strongly that the best job can be done when the manager or supervisor has a real and genuine understanding of his group's work. I don't see how a person can even understand what proper standards are and what performance is required unless he does understand in some detail the very specific nature of the work he is trying to supervise. We have held closely to this philosophy and we intend to continue to do so. We expect you who are supervising to learn techniques of supervision and keep up to date. I want to emphasize you can supervise best when you know a great deal about the work you are supervising and when you know the techniques of supervision as well.

I would never work under em who wasn’t at one point at least a decent developer.