Each manufacturer used his own scale for AOA 'units'. The 104's read
from 0 to 5. At 5 the auto stick kicker kicked. I never looked at the
AOA gauge in the F4 on approach - I used the 'bullseye' indicator and
if the runway was wet it ws the bullseye plus the slow chevron
together. FWIW the F102 with its 60 degree swept delta wing did make
its approach at roughly 15 degrees which happily coincided with the tip
of the pitot boom on the horizon. (Same AOA for rotation and liftoff.)
At 18 degrees you could drag the tailpipe (and P/O maintenance!) I'd
be surprised if an F14 in standard landing config reached 15 degrees
AOA.
Walt BJ