Change of Research Field in Grad School?

[HilarityClinton]

Hello, 

I am an aerospace engineering undergraduate from India. I'm in my final year of a dual degree program, i.e, I'll graduate with a Bachelors and a Masters. 

I'm looking to apply to the US for graduate school in AE for Fall 2017, but I'm having a tough time deciding between fields of aerospace I want to pursue my higher studies in. It is common knowledge that a funded Masters is incredibly difficult to get, but a PhD offer comes with definite monetary support - in the form of TAships or RAships, or any other fellowships. 

My question is, if I get accepted into a PhD program, would it be possible for me to change my PI? And if so, by would I be expected to make that decision?

[Edotdl]

I believe it is generally possible to change your PI at most schools. However, the level of difficulty will vary between schools/programs. In programs that offer a rotation you might not even need to decide on a PI until your second year. While in other programs, your acceptance might be contingent on available funding from a specific PI. In the latter case, in order to switch PI's you will need to find another advisor who is willing/able to support you or find your own funding.

[pterosaur]

The ease of changing advisors definitely varies by school, but it's not verboten. (I've heard the recommendation to go to a school where there are at least 2 people you could see yourself working with, in case things don't work out with your initial advisor for whatever reason - funding, research area, mentoring style, etc.) With rotations, it's definitely easier to switch advisors since you don't really have one until the second year, but I don't think rotations are common in most engineering fields.

In my program, the advisor is "preliminary" for the first year and you have zero obligation to stick with them. However, at another program (CMU) coming in with a masters degree meant that they basically cut off the first year of the program and you were expected to dive in with PhD research right away, making it much harder to change advisors. It's definitely a question to ask when you're doing interviews/visits.