A project manager is supposed to handle:
These are quite diverse functions and you will not easily find all these capabilities combined in one person. First considering the functions that have to be dealt with and then finding the people who can handle one or more functions is recommended.
In a typical development project team at least these functions are always needed:
In a one-person project, one person has to perform all these functions. In a large project
every function may be performed by one or more different persons. Ultimately, however,
there can be only one captain on the ship. That's usually the Project Manager, although I
have seen projects where the Main Systems Engineer performed this function very well.
If it's the Project Manager (s)he may (may have to) delegate the technical decisions and the technical coaching to the Architect/Systems Engineer. Still, ultimately, the captain decides.
Many organisations deliver acceptable software at CMM level 1 (the craftsmen level), because they are staffed with heroes, people who make it happen by experience and excellence. Because these heroes succeed eventually, they gradually get rewarded with management positions, upon which 'normal' people will fill the voids. Pragmatic and proven methods which make normal people deliver Quality on Time (the Right Results at the Right Time) are being collected as Evo Project Management Methods. Notice that many methods for delivering Quality on Time are contra-intuitive, otherwise everybody was already practicing them. Coaching helps to re-adjust the intuition of project management and project team members quickly. That's why I am practicing coaching of projects.
The four levels of Project Management capability:
Explain a typical Project Manager these four levels of Project Management Capability and ask at which level they think they are. In my experience, most will answer, quite honestly, level 2 or 3. Some are very optimistic and say 3½. Using these levels helps making Project Managers aware that there is something they can do about their performance.