Hello: It won't affect your application for Beihang University. If Tianda admits you, you can go to Beihang University after receiving the admission notice from Beihang University before the file is transferred to Tianda University. If the file changes the next day and Beihang University accepts you, you can't go either! One thing to note: once you don't go after admission, the enrollment index of your tutor will be wasted, and you will take the teacher as a spare tire. The circle of doctoral students is small. Once Tianda's teacher is related to or familiar with Beihang's teacher, you will be miserable. Finally, neither school will want you!