How to Check the True Airspeed

As a must to have tool for every pilot student, the E6B flight computer is always very useful and multi-purpose. We can use if for computing time, speed, distance, altitude, true airspeed, and density altitude problems. Conversions, nautical and statute scales, etc. So how to use a flight computer to check the True Airspeed? This blog will show you details, similar like the calculation for speed, time, and distance, we can also use E6B flight computer for checking True Airspeed while knowing its air temperature and pressure altitude data.

True airspeed means the airplane’s actual speed through the air. Normally speaking.. there is little error at cruise speed, and calibrated airspeed always equals indicated airspeed, so we always prefer to use indicated airspeed rather than calibrated airspeed to determine true airspeed.

Here let’s see how to use the flight computer’s front calculator side to check true airspeed.

Rotate the inner scale until the numbers on the inner and outer scales match.
The window on the right side below “2:00” and “2:30” on the hour scale is used to set the air temperature (above the window) over the pressure altitude (numbers in the window).
The air temperature is in 5°C increments from +50°C on the left side to -70°C on the right side.
The numbers in the window are in thousands of feet and range from -2 (or -2,000 ft.) to 50 (or 50,000 ft.).

For Example:

What is the True Airspeed if assume a flight plan with following checkpoint information?

Departure Airport – Pressure Altitude 650 feet
Checkpoint:
Pressure Altitude: 5200 feet
Temperature: 14℃
Indicated Airspeed: 79 kts
Calibrated Airspeed = Indicated Airspeed

  • Rotate the small disc to make sure pressure altitude number 5.2 match to air temperature number 14, as below image shows.
  • Find indicated airspeed 79 on inner scale, read jump cross to the outer scale, which shows 87, it means 87 kt..

So the True Airspeed is 87 kt.

Below youtube performs a how-to-use instruction with CYA aluminum flight computer, hope it is helpful for you!

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