Have 5600 and 5500 Dual screens with separate OAT's in my Evolution. The lowest temperature that is displayed on the screens is -30 deg. C. On many of my flights, I know that the true outside temp at FL 280 is into the -40's, but the units will display no lower than -30 C. Is this a software issue or a limit of the probes themselves? Because of this temp error, the displayed TAS will be incorrect. Can this be fixed through a software or hardware upgrade?
Also, on a recent flight at FL240 determining performance at increasing power levels, the indicated OAT dropped 1 degree C. for every 12-15 knot increase in TAS. For example, at TAS of 237Kts, the OAT indicated -22 C. At 262 kts, it was -21 C., 286 kts it was -20 C; at 306 kts it indicated -19 C, at 312 kts it indicated -18 C. I then slowed back down to 237 kts and the OAT returned to -22 C. Does the algorithm for the OAT display take into account the warming of the probe due to friction with increasing speed?