Aviation & Aeronautics
Intermediate

Equivalent Airspeed

Equivalent airspeed relates true airspeed to sea-level dynamic pressure through the density ratio σ = ρ/ρ₀.

Formula

EAS=TASσEAS = TAS\sqrt{\sigma}

Variables

EASEquivalent airspeed
TASTrue airspeed
\sigmaDensity ratio ρ/ρ₀

Example

TAS 300 kt, σ = 0.44: EAS = 300×√0.44 ≈ 199 kt

Did You Know?

Equivalent airspeed keeps aerodynamic loads constant — structural limits are defined in EAS, not TAS.

airspeedeastasperformance

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