Chris- you applied to be a pilot. Three years later you are considering crewman. This will pose an obvious question.
Why are you now applying to enlist as an SNCO when you originally applied for a commission? This could be taken to mean you are underconfident and lack the initiative, drive and self-confidence to be an effective member of aircrew.
There are many reasons why in three years you have decided that aircrew rather than pilot is what you really want. What you must be prepared for is to articulate why you are seeking NCO rather than Officer status.