What is the purpose of the metal tubing right on top of front pilot ??? It's a blind rigging for instrument flying during day ?
Yes. The trainee has zero external visual visibility but the instructor has full normal views. Good training for nighttime instrument navigation while massively reducing the risks.
Also a good way to test pilots on their instrument navigation skills as part of qualifications.
Once the pilots have fully mastered instrument only fight and navigation, actual night flying is much easier.
The only downside is that such training cannot be a full substitute for night time flight training and ops, and need to be used in conjunction with and leading up to full night time flying, least it inadvertently promotes bad habits like focusing only on your instruments and neglecting frequent all round visual checks.