# True Airspeed Calculator

Calculate True Air Speed (TAS) from Indicated Air Speed (IAS)

## True Airspeed (TAS) Calculator

Note: This calculator is not suitable for supersonic speeds.Simply input the pressure altitude, outside air temperature, and indicated airspeed (knots or mph), and the calculator will dynamically compute the true airspeed using the ISA (International Standard Atmosphere) model for atmospheric pressure and density.

TAS (True Airspeed) is computed from the IAS (Indicated Airspeed) by considering both the Pressure Altitude (which affects air density) and temperature. The calculation involves two main corrections:

**Correction for Air Density/Pressure:**The IAS is first adjusted to account for changes in air density at the given pressure altitude. This is essential because air density decreases with altitude, affecting the performance readings of the aircraft.**Correction for Temperature:**A second correction is applied based on the difference between the OAT (Outside Air Temperature) and the ISA temperature at the corresponding altitude. This adjustment accounts for variations in temperature from standard atmospheric conditions, which also impacts air density and subsequently affects the TAS.

## What is True Airspeed (TAS)?

True Airspeed (TAS) is the actual speed of an aircraft relative to the air mass in which it is flying. It is a crucial metric in aviation because it reflects the airplane's real velocity through the atmosphere, as opposed to Indicated Airspeed (IAS), which is affected by atmospheric conditions like pressure and altitude.

As altitude increases, air density decreases, which makes the aircraft travel faster at the same indicated airspeed. TAS accounts for this change in air density, providing a more accurate measure of how fast the aircraft is moving through the air, especially at higher altitudes.

TAS is important for navigation, flight planning, and fuel management. It also plays a role in determining the actual time en route during a flight, helping pilots make more accurate estimations of their position and arrival time.

**Here are some key points about TAS:**

**Indicated Airspeed (IAS):**This is what the airspeed indicator in the cockpit shows. It's based on the pressure difference between the pitot tube and static port.**Calibrated Airspeed (CAS):**This is IAS corrected for instrument errors.**True Airspeed (TAS):**This is CAS corrected for temperature and altitude. As you climb, the air density decreases, so for a given TAS, your IAS will be lower.

Modern aircraft use onboard computers to calculate TAS based on various factors like altitude, temperature, and pressure. However, there are also manual methods and online calculators available.

## How to Calculate True Airspeed (TAS)?

Calculate Pressure (P) and Temperature (T) using the ISA model based on pressure altitude, then compute Air Density (ρ). Use the TAS formula to compute True Airspeed based on IAS and the density ratio.

### Step1. Calculate Pressure (P):

- For altitudes below 11,000 meters:

P = 101325 × (1 - 0.0000225577 × h)^5.25588 (in Pascals, Pa) - For altitudes between 11,000 and 20,000 meters:

P = 22632.1 × e^(-0.0001577 × (h - 11000)) (in Pascals, Pa) - Where:
- h = Altitude in meters
- 101325 is standard atmospheric pressure at sea level in pascals (Pa)
- 22632.1 is standard atmospheric pressure at 11,000 meters in pascals (Pa)

### Step 2. Calculate Temperature (T):

- For altitudes below 11,000 meters: T = 288.15 - 0.00649 × h (in degrees Celsius, °C)
- For altitudes above 11,000 meters: T = -56.5 (constant in degrees Celsius, °C)
- Where
- 288.15 is the standard temperature at sea level in kelvins (K).
- 0.00649 is the average rate of temperature decrease with an increase in altitude in the troposphere, in kelvins per meter (Standard Temperature Lapse Rate).

### Step 3: Calculate Air Density (ρ)

ρ = (P / (R × T_K)) × 1000 (in kg/m³)

- Where:
- ρ = Air density in kg/m³
- R = Specific gas constant for air (approximately 287.05 J/(kg·K))
- P = Pressure in Pascals (calculated in Step 1).
- T_K = T + 273.15 is the temperature in Kelvin.

### Step 4: Calculate TAS from IAS

TAS = IAS × √(ρ₀ / ρ)

- Where:
- TAS = True Airspeed
- IAS = Indicated Airspeed
- ρ₀ = Sea level standard air density (approximately 1.225 kg/m³)
- ρ = Air density at the given altitude (calculated in Step 1)

## Limitations of this TAS Calculator:

**Altitude Range:**The calculator is accurate only for altitudes up to 20,000 meters (65,616 feet). Beyond this altitude, the atmospheric conditions change significantly, and the formulas used in this calculator are no longer valid. It does not account for atmospheric layers beyond 20,000 meters, such as the stratosphere and beyond.**Subsonic Speeds Only:**This calculator is intended for subsonic speeds and is not suitable for aircraft flying at supersonic or hypersonic speeds, as it doesn't consider compressibility effects that occur at higher speeds.