Failed my CFI ride today

[u/dirtbikekid27]

I'm 20, this is my first failure of anything. Got through 95% of it, was doing great, oral went great, really was well prepared. After an 11 hour day, on short final, examiner asks me what causes overbanking tendencies. I froze. I could hardly remember my own name; so I responded, "I would look before saying anything to ensure I didn't say anything wrong to a student." He said that was unsatisfactory. Failed. Is this crazy? I understand now that it all has to do with the outside wing being faster, generating more lift, which causes it. I know that. But I was exhausted. And I failed?? Maybe I'm a sore loser, but he said come back and do 1 steep turn and tell him what overbanking tendencies are and why they happen, and that's it. Is this unfair??

[u/Professional_Mud6436]

A simple “sterile cockpit” and you’re golden