I would be very interested in understanding where you got the #'s for climb rate when at Vx. I looked at two different C-172 manuals:

https://static1.squarespace.com/stat...C172N-+POH.pdf
and:

http://www.lanierflightcenter.com/wp...s/172S-POH.pdf
Both of them have tables for Vy rate of climbs, and both have tables for Vx and Vy at different altitudes, but NEITHER have a table of actual climb rates when flying at Vx. If you don't have this #, you cannot calculate the angle of climb.

Maybe some of the other aircraft have these #'s, but you claimed ALL cases to have Vy steeper than Vx (which others have pointed out is the opposite of the definition of Vx and Vy).

When testing my COZY MKIV in Phase I, I did complete climb tests at airspeeds from 60 KIAS to 140 KIAS and at fwd, center and aft CG, as well as lightweight, mid-weight and MGW. In ALL cases, the maximum climb angle occurred at a speed lower (by about the right amount) than the maximum climb rate speed - IOW, Vx is always below Vy, and Vx's climb angle is always higher than the climb angle at Vy.

So I think that you're confusing something in the POH with the climb rate when at Vx.

Can you point me to a specific POH where they give the climb rates at both Vx and Vy, and where, if you calculate the climb angle at both speeds, you come up with a steeper angle at Vy?