At other altitudes compressibility error correction may be obtained from a chart.
2.
In practice compressibility error is negligible below about 10, 000 feet and 200 knots.
3.
At any other altitude, EAS may be obtained from CAS by correcting for compressibility error.
4.
Compressibility error arises because the impact pressure will cause the air to compress in the pitot tube.
5.
At higher altitudes CAS can be corrected for compressibility error to give equivalent airspeed ( EAS ).
6.
At high speeds and altitudes, calibrated airspeed must be further corrected for compressibility error to give equivalent airspeed ( EAS ).
7.
In practice compressibility error is negligible below about 3, 000 m / 10, 000 feet and 100 m / s / 200 knots CAS.
8.
With these improvements, a USAAF pilot reported a dive speed of almost 600 mph ( 970 km / h ), although the indicated air speed was later corrected for compressibility error, and the actual dive speed was lower.
9.
Up to about 200 knots CAS and 10, 000 ft ( 3, 000 m ) the difference is negligible, but at higher speeds and altitudes CAS must be corrected for compressibility error to determine EAS . The significance of equivalent airspeed is that, at Mach numbers below the onset of wave drag, all of the aerodynamic forces and moments on an aircraft are proportional to the square of the equivalent airspeed.
मोबाइल