RC helicopter circuit power
LiPo 1S (single cell) gives about 3V fully discharged and 4.2V fully charged.  

3 x AA Alkaline gives 3V discharged and about 4.5V+ newe.

3 x AA NimH gives about 3V to 3.6+V.

So 3 x AA should be OK.
Heli load was probably heavy - AA are OK for a few amps for a while but don't survive long being treated like a LiPo.