Originally Posted by
eckhard
Actually the ASI shows ‘ASIR’, or ‘Air Speed Indicator Reading’.
Correct for instrument errors and you will get IAS, in other words what a perfect instrument would read.
Incorrect, as already stated. ASIR = IAS.
Correct for pressure error and you get RAS (or CAS for Americans).
Negative.
Correct for all system errors - including pressure, and you get CAS (Calibrated Airspeed), known by some Americans as RAS (Rectified Airspeed).
Correct for compressibility and you get EAS.
Correct, but seldom needed below 10,000ft or below 0.6 Mach.
Correct for density and you get TAS
Correct for wind component and you get GS
Correct
But to return to the subject of the thread, I too found it unhelpful back in the day when some US manufacturers marked the ASI dial with colo(u)red arcs, referenced to CAS instead of IAS.
Agreed - Cessna were the biggest offender, but other offenders exist.
G