True airspeed (CAS or EAS adjusted for non-standard?)

[Mattio]

In the IFH, the FAA states:

Equivalent Airspeed (EAS)​

EAS is CAS corrected for compression of the air inside the
pitot tube. EAS is the same as CAS in standard atmosphere
at sea level. As the airspeed and pressure altitude increase,
the CAS becomes higher than it should be, and a correction
for compression must be subtracted from the CAS.​

True Airspeed (TAS)​

TAS is CAS corrected for nonstandard pressure and
temperature. TAS and CAS are the same in standard
atmosphere at sea level. Under nonstandard conditions, TAS
is found by applying a correction for pressure altitude and​

temperature to the CAS.


Shouldn't it say that TAS is EAS corrected for nonstandard pressure and temp (not CAS)??

 

[tgrayson]

Shouldn't it say that TAS is EAS corrected for nonstandard pressure and temp (not CAS)??

Yes.

But to be fair, CAS and EAS are almost the same at the altitudes and airspeeds that we fly in little airplanes. And the random pilot would have a really hard time finding the EAS correction to apply to CAS in order to determine TAS.

 

[fish314]

This link has a chart in the middle of the page that has the correction factor. Also, you can find in on some (but probably not most) E6B calculators in a table form. Unfortunately, I haven't seen my E6B in probably 2 years, and I can't find the table anywhere on the internet.

If you look at the chart, as Tgrayson said, the correction factor is basically 0 until you get above 10,000' MSL and above 200 KCAS. If you are going in the 100-150 knot range, there is basically no correction until 20,000' MSL... and then it's only about 1 knot.

Now if you are talking about an airplane in the 200 and above range, it's a different story. A fighter going 500 knots could have a correction of up to 6 knots (from CAS to EAS) as low as 5000' MSL

 

[Mattio]

Ok, thanks guys