time dynamicsThere is perhaps a notion that PERT-CPM is the precise way to plan a project and that therefore overruns are the fault of the people of the project, human factors. However it is a deeper problem then that in that there are some underlying assumptions in the PERT-CPM planning method that mean although it can work well in large production projects it may not work so well in small development project.
Large production projects tend to be project driven, people are hired as required to perform specific roles for known durations. A prime objective of the organisation is to complete the project in the minimum amount of time. The people are often contractors employed specifically to meet labour requirements. It is possible to hire any number of electricians, plumbers etc. They simply plug into the project because the project design drawings, methods etc. are all in standard language and also the roles are standardised.
Small development projects tend to be people driven, they are performed by a known and tested team of people each bringing particular capabilities to the project. A prime objective of the organisation is to keep that team effectively employed. The team might be working on multiple projects at any one time taking advantage of the synergies and interleaving work.
In small development projects, even if tasks and predecessor relationships are known, the project is very likely to depend on the special abilities of individuals in the organisation, one can't simply hire x people with the special ability to innovate.
Innovation is typically achieved by small teams of known people. Thus rather than a "project driven approach" we have a "people driven approach" where the availability of people typically controls the project. This has the potential to descends into a "scrum" as people throw more formal methods out the window.
However Chronograph supports agility within formal methods like Critical Path Method so there is every chance to retain a longer term schedule within the project.
There is a very interesting interview called Some Reflections on PERT and Project Management with Charles S. Enright and Robert L. Hamilton (retired), from MITRE Corporation as interviewed by Ronald M. Lehrer, from Systematic Management Services, Inc.