When I first interviewed, I was living across the country so the initial interview was over the phone with the current HR employee at the time. This was a long interview with approximately 30-40 questions more typical of general interview questions (describe yourself, what you would do if a co-worker isn't pulling their weight etc).
After completing a successful phone interview, I then took a pre-employment aptitude test that tested critical thinking, attention to detail, ability to remember new information etc.
I was then extended a Skype interview (this was in place of the in-person interview due to travel constraints being located cross-country) with 4 of the PE's in the office and the gentleman in HR in charge of hiring (same person from phone interview). Very standard interview questions and with more questions regarding specific experience with types or design, materials, engineering etc. With as many people in the room, the interview became more conversational which was nice and helped with nerves.
Immediately following the Skype interview, I received a phone call from the gentleman in HR I had been working with closely through the whole process to debrief on how the Skype interview went which I appreciated the feedback on how I interviewed and how they received my interview greatly (he also gave the same sort of feedback following my phone interview with suggestions on how to improve/what kind of answers he liked for any future interviewing I would do which was very much appreciated!)
After the Skype interview, I was then extended an in-office visit that resulted in an in-person offer I gladly accepted!
Overall a very standard and organized interview process!
General timeline was as follows:
Inquired about the position mid-april (4/14)
Received a response 2 weeks later (4/28) saying my application was received
Phone Interview happened approximately a month later (5/22)
Skype Interview happened shortly after (5/30)
In-Person visit was scheduled shortly after (6/1)
Offer extended the following week (6/6)