‘Y’ means it was the second prototype batch after ‘X’. Sometimes the Ys would be modified with the final spec and enter service but typically they would lose the Y designation at that time. For instance the prototype YB-36 entered service as a reconnaissance RB-36A after modifications.
‘Y’ means it was the second prototype batch after ‘X’. Sometimes the Ys would be modified with the final spec and enter service but typically they would lose the Y designation at that time. For instance the prototype YB-36 entered service as a reconnaissance RB-36A after modifications.