What is the difference between indicated airspeed and true airspeed and which is typically monitored in IMT 1?

• A. Indicated airspeed is what the cockpit shows; true airspeed is the speed through the air; IMT 1 primarily uses indicated airspeed.
• B. Indicated airspeed equals true airspeed in all conditions; IMT 1 uses true airspeed.
• C. Indicated airspeed is what the cockpit shows; true airspeed is actual speed through the air; IMT 1 primarily uses true airspeed.
• D. Indicated airspeed is the speed relative to the ground; true airspeed accounts for wind; IMT 1 uses indicated airspeed.

Answer: (C)

Indicated airspeed and true airspeed measure two related but different things. Indicated airspeed is the number you read on the airspeed indicator—the speed shown in the cockpit—based on dynamic pressure sensed by the pitot tube. It isn’t corrected for instrument errors, compressibility, or changes in air density. True airspeed is the actual speed of the airplane through the air, corrected for those factors like density and compressibility.

Because air density decreases with altitude (and changes with temperature), IAS and TAS diverge as you climb: TAS generally becomes higher than IAS at higher altitudes for the same indicated reading. This distinction is important for understanding performance and flight planning.

In IMT 1, the focus is on understanding how the aircraft performs under different density conditions and how altitude and temperature affect speed through the air, so true airspeed is the primary reference used for performance considerations. The reading shown in the cockpit (IAS) is still used for immediate control, but TAS is the more informative measure when evaluating performance envelopes and adjustments for altitude and wind.

Other choices aren’t accurate because the indicator shows a cockpit-reading speed (not ground speed), TAS is not the same as IAS in all conditions, and ground speed differs from both IAS and TAS since it’s corrected for wind.