True Airspeed Calculator
Calculate true airspeed (TAS) using multiple aviation methods and formulas
Calculate True Airspeed
Airspeed indicator reading
Aircraft altitude
Outside air temperature correction
Formula Used
Density Ratio Method: TAS = IAS × √(ρ₀/ρ)
Where: ρ₀ = sea level density, ρ = density at altitude
Example Calculation
Commercial Flight Scenario
Aircraft: Boeing 737 at cruise altitude
Indicated Altitude: 35,000 feet
Calibrated Airspeed: 280 knots
Outside Air Temperature: -40°C
Altimeter Setting: 1013.25 hPa (standard)
E6B Calculation Steps
1. Calculate pressure altitude: 35,000 ft (standard conditions)
2. Standard temperature at 35,000 ft: -54.3°C
3. Temperature deviation: -40°C - (-54.3°C) = +14.3°C (warmer than standard)
4. Density ratio calculation using ISA formulas
5. TAS = CAS / √(density ratio) ≈ 465 knots
Result: True airspeed significantly higher than indicated due to thin air at altitude
Airspeed Types
IAS - Indicated Airspeed
Raw reading from airspeed indicator
CAS - Calibrated Airspeed
IAS corrected for instrument errors
EAS - Equivalent Airspeed
CAS corrected for compressibility
TAS - True Airspeed
Actual speed through the air mass
Performance Categories
<100 kt
Light aircraft, trainers
100-250 kt
General aviation
250-450 kt
Turboprops, regional
450-600 kt
Commercial jets
>600 kt
High-performance, military
Calculation Methods
Rule of Thumb: Quick altitude correction
Vector Method: Ground speed and wind
E6B Computer: Precise ISA calculations
Applications: Flight planning, navigation
Understanding True Airspeed
What is True Airspeed?
True Airspeed (TAS) is the actual speed of an aircraft relative to the air mass in which it is flying. Unlike indicated airspeed, TAS accounts for air density changes with altitude and temperature, providing the real speed through the air.
Why It Matters
- •Navigation: Essential for accurate flight planning and timing
- •Performance: Determines actual aircraft performance
- •Fuel Planning: Critical for fuel consumption calculations
- •Air Traffic: Used by ATC for separation and sequencing
Altitude Effects
As altitude increases, air density decreases significantly. This means that for the same indicated airspeed, the true airspeed will be higher at altitude. This is why jets cruise at high altitudes - they can achieve high true airspeeds while maintaining manageable indicated airspeeds.
Practical Applications
- •Flight Planning: Route timing and fuel calculations
- •Weather Analysis: Wind correction and ground track
- •Performance Testing: Aircraft certification and testing
- •Air Traffic Control: Separation and flow management
Calculation Methods and Formulas
TAS = IAS × √(ρ₀/ρ)
Basic density correction formula
TAS = GS - W × cos(θ)
Vector calculation from ground speed
M = TAS / a
Mach number relationship
a = 38.94 × √T
Speed of sound in knots (T in Kelvin)
• Higher altitude → Lower density
• TAS > IAS at altitude
• Rule: +2% TAS per 1000 ft altitude
• Higher temperature → Lower density
• Hot day → Higher TAS
• Cold day → Lower TAS
• Compressibility effects above M0.3
• Critical Mach number considerations
• Maximum operating limitations