i was interested to do aeronautical engineering.what was the process is to study.?is there any entrance exam separately for this?how much rank we have to get in amcet and jee main?

HELLO DAVID

You don't need to write any separate exams for aeronautical engineering. But it is sad to hear that NO NITs offer aeronautical engineering.If you wish to study in the most reputed colleges which offers aerospace which is very much similar to aeronautical engineering then only IIT kanpur,madras,kharagpur,mumbai offers this course. So in order to get into it you must first qualify JEE mains with a percentile above 90+ just to be on safer side note you may not get top NITs with this percentile. so issues you to grab a percentile above 99+ so that top 5 nits should be already in your pocket as alternative. Fate qualifying JEE mains then you need to score and grab a good rank in JEE advance so that you get this IIts.
now in india there are many institutes which offer aeronautical engineering>

There are alot of colleges in karnataka which offer aeronautical engineering in order to take admission if you are not living in karnataka then you need to write a excam called COMEDK which will lead you into this institute and this exam is very easy to crack.

Now ill provide you a link of all the engineering college providing aeronautical engineering course in india.

https://engineering.careers360.com/colleges/list-of-aeronautical-engineering-colleges-in-india

HOPE IT HELPS!!