Originally Posted by
Pugilistic Animus
Like others have shared it is a function of TAS
Vx is the greatest difference in power required and power available. Whereas Vy is the greatest difference between thrust horsepower required and thrust horsepower available where thrust horsepower = Thrust* Velocity (TAS)
It is not a function of TAS. The question is why in that particular AFM the Vx at 10,000' is quoted as higher than the Vy at 10,000'. Vx cannot be faster than Vy at any given weight and altitude, it is impossible and it doesn't matter whether you are tallking CAS or TAS. The OP has asked if it could be attributed to position error, in other words IAS vs CAS. I say no but would be happy to read a cogent explanation that addresses the question actually asked.