Originally Posted by
Machdiamond
Flight manual of A-1B says absolute ceiling is 16000ft (by extrapolating the climb curves at ISA temperatures from 6000 ft to 10000ft)....Another potential explanation besides a typo is that Aviat does not like recommending climbing at that speed and decided to pad some margin on VX, because it is so close to stall speed on that aircraft.
And yet the slower Vy remains so that doesn't make any sense. I think the most plausible explanation is the other one you gave ie:
the A-1A is basically the same aircraft as the A-1B and has all similar performance data except, suspiciously, Vx which is 58MPH at sea level and 60MPH at 10000 ft, likely the correct values for the A-1B give or take a knot.
Also, the AFM says that in the case of alternate static "No airspeed correction necessary". Although it is not definitive, this suggests that the position error is not a significant factor.
Edited to say: under 'Balked Landing' in the AFM the sea level Vx is quoted to be 74 mph (!). Also, according to their 'Normal Procedures' the climb speed to be established for max performance take-off is 65 mph whereas in the performance section they quote 70 mph for the max performance take-off. All in all I think it is fair to say that Aviat (and the FAA) have made a right old mess of getting the performance data into the manual.