Hi,
I say you my problem :
I have an ASI, an EFIS 100 and a GPS. During a flight, the speeds giving by these instruments are similar : 150 kph by ASI, 145 kph by Efis and 152 kph by GPS.
However, when I make some stalls, (the stall come from 65 kph by ASI, and it is the correct speed stall)...