An 18/19 credit is typical for tech, but not for non-tech because non-tech students don't take 4 credit classes. They take 3 credits, thus, the majority of them will take 5 classes at 3 credits, and 1 for LLAB.
Our DS as a govt major did carry 18/19 credits, but that was because he was in the scholars program at his school, and they automatically had to take the scholars seminar, plus do an internship, which gave him the 18/19 varying each semester.
Our DD is an education major, but started off as a Psych major, she takes @16, and only had 1 semester she took with 17, because they require Math and Sci., so those 2 classes were 4 credits each, her other 3 classes were 3 credits.
Your assumption is each and every class is 4.0. Our DD currently is carrying 15 credits, but only 4 classes, 1 is 5 credits, 1 is 4, and 2 are 3 credits. He too is a non-tech major.
I don't know anyone that can handle a 28 credit course load in 1 semester. Most colleges will not only charge you a fortune to go over 18-20 credits, but you need approval by the advisors.
Now if you are saying 28 over a yr. There still is a problem because for the AFROTC 3 yr ISS, you apply and board after the 1st semester of your freshman yr. So if the D is in that 1st semester you will be in trouble.
Also colleges vary regarding grading. Some will do the A+=4.0, A=3.8, A- = 3.6. Some will do actual percentage. 93 x 4.0 = 3.72, there is no + or -, just pure grade. At DS1 school they took out his cgpa to the 1/1000th. i.e. 3.721 = 3.72, 3.725 = 3.73. I know that for a fact because he had to carry with his merit scholarship at all times a 3.20. One semester it was 3.194 and they rounded it to 3.19, and placed him on academic probation for his scholarship. I was floored and to this day remember saying are you flipping kidding me?
We never looked at the fine print, and it did indeed say 3.20 not 3.2. It didn't say cgpa, it said gpa. This is a kid who got a 3.6 the semester prior, and now they were telling him that one more semester at 3.19, even though the cgpa would be above 3.20, it would be revoked. He never ever did it again. I think the lowest after that was a 3.34.
The point still isn't about how you get to that 3.5, it is academically you can be that 3.8 uwcgpa with all APs, but that fall freshman semester is not HS, and don't expect that you will be able to maintain a 3.8.
Our rule of thumb in our home is simple:
1. No Fs
2. 3.0 gpa.
Get a C in one class, you better have an A in another. We understand that each of them have academic strengths and weaknesses. Our DD is not mathematically gifted, it comes with tons of studying, whereas English she doesn't need to crack a book open. Our boys are the opposite. It is okay to get a C in your weak subjects.
I can't stress hard enough that for AFROTC as a non-tech major, a 3.3/3.4 is mid range. SFT selects @60% and 3.3/3.4 has been the avg cgpa for non-techs. No SFT= No commissioning.
If that cgpa is the avg., and ISSP offer less scholarships than HSSP, it does not take a lot to follow the trail to realize 3.5 might not cut it, and a 3.6 might be the cusp.
AFROTC really truly places a lot on wanting STEM majors. When our DS was a C400 and saw the incoming stats of the C100s HSSP recipients he said to us, if I applied against them as a non-tech, I am pretty sure I wouldn't have received a scholarship.
There was a poster here, her DS went to a magnet school, had great stats, and he got the TWE. He eventually got an ISS as a freshman.
Finally, one thing for anyone that is contemplating this path if they get the TWE for HSSP. Please, please, please, keep taking the SAT/ACT until you graduate.
AFROTC only uses best sitting, but for some their best sitting goes up because their academic classes are still building that foundation, and for others they have learned how to take the test.
That SAT/ACT will be part of your SFT board selection score. The avg SAT for scholarships range between 1270-1350 best sitting. They will be your competition, and if you have 1220, plus are non-tech, you are playing catch up with PFT, and Commander recs.
It is why many cadets join AAS, Angel, Silver Wings, Honor Guard because all of those organizations have Cadre advisors and now they are not a name only, they have a face too. Their advisors know them from another side. They can see it differently.
The thing with AFROTC which is totally different from AROTC is that C200 yr. SFT is the LDAC equivalent, but the difference is if not selected for SFT as a 200, they can be dis-enrolled at that point. If not selected the CoC can allow them to become a 500, but the problem is they are what the AD world calls Above Zone, and statistically it can become even harder to get the slot. CoCs only do this now if they are willing to stick their neck out with AFROTCHQ because of the DoD budget for ROTC. They are O6s they know the system.
AF is the smallest of the 3 ROTC branches. They require AD, there is no Reserve/Guard option, thus they have to have that cut yr. Planning 4 yrs out is difficult, but 2 yrs out is easier, and thus the C200 make or break.