Q: My both iPad Air and ipad 2 don't discover over each other when Bluetooth is switched on... Any help?

This is expected behaviour, as there is no supported protocol to make that connection.

http://support.apple.com/kb/HT3647

iPad 2 does not support AirDrop.

The Bluetooth function of any iDevice will be to connect keyboards, speaker, headphones, Automobile bluetooth systems. They will not connect to each other for purposes of file transfer.

my ipad air2 will not connect via Bluetooth to any device despite my iPhone 5s connecting with no problems.  I even bought the apple wireless keyboard and the ipad air 2 will not even connect with this,  it's very frustrating!!