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For the Airbus A380, the largest passenger aircraft ever built, you are given the following parameters:

Variable Value
Mass 500,000 kg
Wing Area 845 m2
Wingspan 79.75 m
Number of Engines 4
CLmax flaps retracted 1.9
CLmax flaps extended 2.6
Oswald Efficiency Factor 0.92
CD0 0.022
Flight Parameters
0.0/3.0 points (graded)
An Airbus A380 is flying in steady, horizontal flight at Flight Level 280.

The pilot reads an Indicated Airspeed (IAS) of 290.0 kts. Calculate the True Airspeed (TAS) in kts

1 answer

To convert Indicated Airspeed (IAS) to True Airspeed (TAS), we need to account for the altitude effects on air density and pressure.

At Flight Level 280 (FL280), which is approximately 28,000 feet, we can find the following parameters:

  1. Standard atmospheric pressure decreases with altitude. At FL280, the pressure is approximately 28.4 inHg (or 966 hPa) or around 0.91 atm.
  2. The temperature at FL280 is typically about -2.0°C, which corresponds to about 271.15 K.

Find the Pressure Ratio

Using the International Standard Atmosphere (ISA) model:

  1. Convert IAS to CAS (Calibrated Airspeed):

    • The relationship can be approximated with a small altitude correction and is usually small enough for general estimates unless precise data is available.

  2. Convert CAS to TAS:

    • TAS can be calculated using the following relationship: \[ TAS = IAS \times \sqrt{\frac{P_0}{P}} \] Where:
    • \(P_0\): Standard pressure at sea level (1013.25 hPa)
    • \(P\): Pressure at flight level (966 hPa)

Effective Calculation

  1. Calculate the pressure ratio:

    • \( \frac{P_0}{P} = \frac{1013.25 , \text{hPa}}{966 , \text{hPa}} \approx 1.0487 \)

  2. Convert IAS:

    • Given: IAS = 290.0 kts
    • Calculate Tas: \[ TAS = 290.0 \times \sqrt{1.0487} \approx 290.0 \times 1.024 = 296.96 , \text{kts} \]

Result

Therefore, the True Airspeed (TAS) of the Airbus A380 at FL280 with an IAS of 290.0 kts is approximately 297.0 kts when rounded to one decimal place.