How to calculate true airspeed
True airspeed (TAS) is a crucial parameter in aviation, as it provides pilots with an accurate measure of their aircraft’s speed relative to the surrounding air mass. Calculating true airspeed can be a bit complex, but with the right understanding of the underlying principles and formulas, it becomes a manageable task. This article will walk you through the process of calculating true airspeed step by step.
Step 1: Gather the Necessary Data
Before starting, ensure you have all the necessary data available. To calculate true airspeed, you will need:
1. Indicated Airspeed (IAS): The airspeed read directly from the aircraft’s airspeed indicator.
2. Pressure Altitude: The altitude calibrated for standard atmospheric conditions (29.92 inches of Mercury or 1013.25 hPa).
3. Temperature: The outside air temperature in degrees Celsius.
Step 2: Determine Calibrated Airspeed (CAS)
Calibrated airspeed (CAS) is a corrected version of IAS that accounts for instrument and position errors. Some modern aircraft provide CAS directly on their display; however, if it needs to be calculated manually, refer to your aircraft’s Pilot Operating Handbook (POH) or an online calculator.
Step 3: Calculate Density Altitude
Density altitude is the altitude at which the aircraft “feels” like it’s flying due to non-standard temperature and pressure conditions. To calculate density altitude, use either a flight computer (manual or electronic), dedicated app, or an online calculator.
Step 4: Determine True Airspeed Using the TAS Formula
The formula for true airspeed is:
TAS = CAS × √[288 + Outside Air Temperature (OAT)] / 288
– TAS is True Airspeed in knots
– CAS is Calibrated Airspeed in knots
– OAT is Outside Air Temperature in Celsius
By plugging in the values for CAS and OAT from steps 2 and 3, you can calculate your TAS.
Alternative Step 4: Using Flight Computers or Apps
An alternative to using a formula is an aviation calculator, flight computer, or app that can compute true airspeed. Simply input the required data (CAS, pressure altitude, and temperature), and the device will instantly provide you with the calculated TAS.
Calculating true airspeed is essential for various aspects of aviation, including flight planning, navigation, and performance optimization. By understanding the principles behind TAS and following this step-by-step guide, pilots can accurately determine their true airspeed during any phase of their flying endeavors. Whether manually calculating TAS using the formula or relying on technology like flight computers and apps, having an accurate TAS reading significantly improves flight safety and efficiency.