Hello,
I agree with your thought, but it can't happen all the time . Mangers use several different kinds of tools to create draft schedules .These include bar charts, flow charts, and PERT charts.I will discusses in detail below. Bar charts show project stakeholders how project is progressing. A Gantt chart is one example. should show the following : 1) Task status;completed tasks are shaded out 2) Estimated project duration 3) Estimated task duration 4) Task sequence and task completed in parallel.
Flow charts helps your team closely manage and communicate project details to your supervisors and project team members. As mentioned in the this week lecture a critical path diagram is one example.Any delay in the critical path will delay completion of the entire project.
PERT(Performance evaluation and review technique) charts shows when every project task within a phase should begin , how much time is scheduled for each task, and when each task should be completed. The chart also shows all task in progress at a given time and all the dependencies between outcomes, tasks and events. No matter how experienced you are , don't rely just on your instincts. To succeed, you need to use project management tool. Always expect the unexpected, anything can happen during a project.

There are many different things that could happen that will cause pitfalls. As you mentioned team members taking time off is one such circumstance that could occur that may cause a pitfall. In Dr. Simon’s lecture, he also mentioned not accounting for risks, holidays, other projects, and estimating way off as some ways that a pitfall can occur. Some things I could think of is improper research and ignoring spec. if not enough research is done on let’s say the material that the product will be made of, this can present issues. Such as if the team is designing an orthopedic implant and uses a certain type of metal because it’s strong, but neglects other properties like corrosion resistance. That can cause a pitfall in the testing phase of the project. Proper guidelines and planning can help to alleviate potential pitfalls from happening but sometimes the unexpected can happen which no one saw coming.

Although proper use of project management tools can definitely mitigate the risk of pitfalls, as wms7 mentioned, even in relatively simple projects, the unexpected will almost always happen. However, when you use these tools effectively, they can be very useful in managing unexpected events that do occur. If you keep your Gantt chart updated, it is very simple to assess the impact of the unexpected event on all of the tasks in the project, and it can be adjusted to see how tasks can be moved around to have the least impact on the project. If you are not using project management tools properly, this process of reassessing and deciding upon a path forward can take much longer and will be very inefficient.

I think that not doing enough research could lead to more pitfalls. The more research you do the more you can expect and prepare for when things come up. Research also includes looking into calendars and schedules of the people on your team. They all need to know the dates they are needed and compare that to their schedules to account for vacations, doctors appointments, and other days they plan to not come to work. They might bring things up that you forgot about. Expecting the unexpected should be applied to a gantt chart by adding in slack time so that deadlines aren't missed. You want to add enough time so that you have a cushion but not too much to where there is time wasted for excessive task times. Pitfalls also occur when resources you need are not readily available when you need them. Planning involves plotting out what needs to be done but making sure everything you need to complete them is accounted for.

Adding to the discussion, another pitfall in Gantt chart that if you have poorly defined CAPA time-frames.
CAPA which means establishing a corrective and preventive action system, which is required in (QSR) a quality system regulation for medical device for marketing products in the united states.
Solution: So, you must clearly define how long each phase of your CAPA will take, provide appropriate rationale for activities that will take a long time to implement, and explain what you plan to do if you go beyond the specified time-frame. It is important to have defined time-frame criteria for CAPA resolution as part of your CAPA procedures.

I agree with @srg36 that even if you use project management tools like Pert charts, Gantt charts, there will still inevitably encounter pitfalls, but you will be able to more effectively manage these scenarios with these management tools. As Dr. Simon mentions in lecture, it is important not only to schedule the tasks but to account for costs and resources before the tasks are known. The common pitfalls that arise in the planning phase in regards to costs; making up costs before you know the tasks, estimating costs without having planned the tasks or have done your research, and not accounting for risks and contingencies. Similarly the common pitfalls that arise in regards to resources include as @cdj24 mentions; not accounting for vacations/holidays, contingencies, other projects, and making commitments before tasks are known. Overall, I agree with @srg36 that this can managed effectively by having a robust Gantt chart so that you can adjust as necessary and have an up-to-date timeline on tasks/sub-tasks to manage the project. As Dr. Simon mentions MS Project has the ability to take into account holidays/vacations so there are ways to address and mitigate these common pitfalls.

In the PMBOK guide Chapter 4 provides an overview of the Project Integration processes which include; Developing a Project Charter, Developing a Project Management Plan, Directing and Managing Project Execution, Monitoring and Controlling Project Work, Performing Integrated Change Control and Closing the Project or Phase. I think Figure 4-5 is a Data Flow Diagram of the intricacies of developing a Project Management Plan. For example, this includes; Defining Scope, Creating WBS, Determining Budget, Developing Schedule, Plan communications, etc.

Like many have stated, some pitfall will occur. Things like holidays and days off could slow a team down. That is why many teams and companies use gantt charts, to organize their tasks. I believe as a team or an organization, we need to be better prepared. There will be times when coworkers will could cause a delay in a project, but as a team we would need to prepared for any setbacks. In the lecture, we learned it is better to plan ahead. I believe teams should have weekly meetings and divide work, or create a timeline or contingency plans to avoid any setbacks. I remember in capstone, if we fell behind the weekly task, we would have to come up with a contingency plan, so we could avoid falling behind our schedule.

Scheduling time for each person to complete assignments is definitely a bottleneck or can become one. One way to get around this is to schedule around the persons personal time off and have them approve of it. Another potential setback is shared resources. So on my team, several of us are on different teams so the project manager and leads have to balance resources well so the projects are completed.

I agree with Parth that planning ahead is important to avoid this type of pitfall. During these weekly meetings, they should set a goal for what should be done and make sure they meet it. So if a person mentions they will be going on vacation or if there is a holiday, during the weekly meeting they can discuss what work they need to get done before they go. You should have a conservative plan and an aggressive plan as well. This will allow you to have a more realistic goal as well as what more can be done if you speed up certain processes.

I agree that a major pitfall is scheduling conflict as many team members will not always be available and team members taking vacations and time off can severely impact the time line of the project. In addition, I do believe that another major pitfall would be a lack of necessary resources to complete the project. This can result from a budgeting problem where a subgroup is unable to get their necessary supplies to complete their part of the project. Therefore, this will hold up the other team subgroups as they can not follow through on their part of the project if the schedule is set to happen in chronological order. Also, a major pitfall too with resources is if something breaks or becomes damaged in the process of manufacturing or shipping and now the team has to redo their work, which may force other teams to do more work and stop other teams from completing their work. In addition, the planning phase goes over creating an estimated activity duration for each subset of the project. This is just an estimate though and some tasks may take a lot longer to complete which can mess up the time table and push the project back further and further. In addition, another pitfall could be not identifying all potential risk, and then running into unexpected complications later on that can halt the project. If a project team can effectively create a successful scope and make sure they are as accurate as possible with estimated costs and time then a project team can avoid pitfalls and major complications.