a (hopefully) simple quaternion question

Say my aircraft is in a current orientation of phi (roll, x-axis) = 0 degrees theta (pitch, y-axis) = 30 degrees psi (yaw, z-axis) = 20 degrees
which corresponds to a quaternion Q = 0.952 + 0.045i + 0.255j + 0.168k
But my desired orientation is phi = 0 degrees theta = 0 degrees psi = 0 degrees -OR- Q = 1 + 0i + 0j + 0k
If I am thinking in terms of Euler notation, then I know there is a pitch error of 30 degrees and need to deflect the elevator to correct this. Likewise, the 20 degree yaw error must be countered by rudder deflection. However, if I'm thinking in terms of quaternions, then how can I go about this?
Thanks in advance, weg
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