is a 2013 ipad air 2 dual voltage for travel to europe, or will i need a converter?

All Apple iPad USB and USB-C power adapters are designed for use with power sources rated to provide 100V AC to 240V AC at 50Hz to 60Hz. Apple iPad USB power adapters also comply with the IEC/UL 60950-1 and IEC/UL 62368-1 standards for use with power sources rated to provide 115V AC at 400Hz (typically found onboard commercial airlines).

While your Power Adapter will be fully usable when travelling internationally, you may require a simple pin-adapter to allow the Power Adapter to be used with AC power outlets in different countries. For example, a US flat 2-pin connector will require an adapter for the standard European round 2-pin socket - or UK 3-pin square socket. Travel adapters are readily available.