Standard Day - Standard Day Parameters

Standard Day Parameters

For Pilots: At sea level, Altimeter:29.92 at 59 degrees F(15degreesCelcius) The "standard day" model of the atmosphere is defined at sea level, with certain present conditions such as temperature and pressure. But other factors, such as humidity, further alter the nature of the atmosphere, and are also defined under standard day conditions:

  • Density (ρ): 1.229 kg/m³ (0.00237 slug/ft3)
  • Pressure (p): 101.3 kPa (14.7 lb/ in2)
  • Temperature (T): 15 °C (59 °F)
  • Viscosity (μ): 17.3 µPa·s (3.62 × 10-7 lb s/ft2)

The first three properties are usually referred as "standard day" conditions, which the viscosity aspect is largely ignored throughout the aviation community. However, viscosity, which is affected by humidity levels, plays a key role in aerodynamic drag, which is why it is a key component of standard day conditions. Because it is a key component of drag, it affects the amount of fuel burned per unit of distance travelled.

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