The spiral staircase analogy works well for both climbing and descending once you are clear that the handrail represents the relative airflow coming towards the wing.
The descending case is straightforward, as you say. The climbing case just needs some visualisation. Now, forgive me some simplification for clarity ...
Imagine the aircraft heading up the staircase. The chordlines of the both wings have the same upwards angle to the earth's surface. Despite the fact that the aircraft is climbing, the relative airflow approaches both wings from underneath the wing.
As the aircraft moves forward, the inside stair rail is coming down towards the aircraft from a higher vertical position than the outside rail. So the angle between the wing (chord) and the inside rail (relative air flow) is small.
The outside stair rail is coming towards the aircraft from a lower vertical position than the inside rail. So the angle between the wing (chord) and the outside stair rail (relative air flow) is greater, and the outside (higher) wing has a greater angle of attack.
Last edited by Unhinged; 28th Oct 2009 at 09:43.