TAS question...

[kingAirB20]

i've been a bit stuck on a question i was asked in my CAA examination... could any one shed some light here?

TAS:

-IAS corrected for temperature and altitude
-IAS corrected for instrument error
-RAS corrected for instrument error
-RAS corrected for temperature and altitude

[Private jet]

The last one. RAS is IAS corrected for pitot tube position errors etc, and TAS is RAS then adjusted for non standard air density which varies with air pressure and temperature.

[eckhard]

This is my understanding of the various different speeds that can be used and their corrections:

ASIR - Air Speed Indicator Reading; the uncorrected reading of the instrument.

IE - Instrument Error; a correction made for errors in the construction and calibration of the instrument.

IAS - Indicated airspeed; ASIR corrected for IE.

PEC - Pressure Error Correction; a correction made for erroneous static port measurements caused by the position of the port and the local airflow disturbance cuased by airspeed, altitude and configuration.

RAS - Rectified Air Speed; IAS corrected for PEC.
CAS - Calibrated Air Speed; US term for RAS.

CE - Compressibility Error; the error induced by the increase in apparent air density at high speeds due to the compressibility of air

EAS - Equivalent Air Speed; the RAS or CAS corrected for CE. This is the speed that the aircraft 'thinks' it is flying at.

DE - Density Error; an error due to the fact that pitot pressure at a given speed varies with air density. The instrument is calibrated to read correctly with an asssumed air density of 1.225kg per cubic metre (i.e. the air density at sea level in the ISA)

TAS - True Air Speed; EAS corrected for DE.

So I agree with Private Jet; the answer is the last one. (I would say however that pitot errors are negligible compared to static errors.)