Comment on measuring OAT which is only an issue beginning above maybe 200-250 knots.  If the OAT measurement is made outside of the air stream (like the skin temperature, for example), it is still subject to aerodynamic frictional heating.  One can calculate this via something called the Recovery Temperature which varies a bit from stagnation temperature rise.  But for our purposes, the recovery temperature rise (which is effectively the skin temperature on unheated parts of the airframe) is about 80% of the stagnation temperature rise.  In short, there is no way to avoid the aerodynamic heating error.  It goes as the square of the TAS.  You have to allow for it.  It is always there, and it will always create an error when you calculate corrections with your E6B. 

Fred,

 

Ahhh, error is in the calculation of the beholder.......

 

Fortunately, those utilizing the Rocky Mountain Instrument's micro encoder note that it displays KTAS (corrected for compression temperature rise) and TAT.  In other words, my TAS calibration based on quality GPS data over a 3 or 4 legged course really is within a Knot.  Airspeed and TAS from my temperature/altitude corrected analog airspeed steam gauge varies a bit from the RMI device. 

 

I would have to assume that all of the modern EFISes, widescreen video cockpit displays, fancy-dancy synthetic vision devices, MFDs, etc. more properly calculate a compensated TAS, whether in Knots, MPH, KPH, or Furlongs per Fortnight (FPF) - depending of your choice of scale.

 

I could be wrong - nothing new for me....