Hello Aspirant.

No, 11th Appearing Candidates are Not eligible to apply for NDA Examination. 

.WHAT IS NDA? 

NDA Stands for National Defence Academy examination and this examination is Conducted by UPSC, Twice in a year for the Recruitment of these 3 Wings :-

.Army Wings

.Naval Wings

.Air Force Wings

.Educational Qualifications: -

 You have to complete your 12Th examination with Maths and Physics as a compulsory Subjects, then only you are eligible for all the wings of NDA.

. Age: -

Your age should between 16.5 to 19 Years.So, please complete your 12th examination first and then you are eligible to apply for NDA Examination. 

I hope my answer will help you, do revert back in case of any confusion. 

Hi 

This is Ritika

As per NDA eligibility criteria student must be 16.5 to 19.5 years old and must be appeared or to appearing for 12th exam.So you are in 11th so you are not eligible now you will be eligible from next year .

All the best

Hope my answer helped you

Thank you