Crossover Altitude Calculator
Find by bisection the altitude where a constant Mach number and a constant calibrated airspeed correspond to the same true airspeed.
Description
Find by bisection the altitude where a constant Mach number and a constant calibrated airspeed correspond to the same true airspeed.
Crossover Altitude Calculator provides a focused, reproducible calculation with explicit inputs and a deterministic result. Find by bisection the altitude where a constant Mach number and a constant calibrated airspeed correspond to the same true airspeed.
Use for an approximate ISA crossover altitude between a selected calibrated airspeed and Mach number.
When to use Crossover Altitude Calculator
Use for an approximate ISA crossover altitude between a selected calibrated airspeed and Mach number.1
How the calculation works
Find by bisection the altitude where a constant Mach number and a constant calibrated airspeed correspond to the same true airspeed.2
Solve approximate constant-CAS TAS = constant-Mach TAS Inputs and interpretation
Keep every input on the same valuation, timing, unit, and assumption basis. Interpret the output at the precision supported by those inputs rather than treating extra decimal places as additional certainty.
Limitations and assumptions
The compact equations are an approximation and do not replace the aircraft climb schedule, compressible-air data, operating limits, or flight-management computation.
References
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AC 25.1581-1: Airplane Flight Manual — Federal Aviation Administration
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International Standard Atmosphere — Wikipedia contributors
Similar or alternative tools
- Mach Number Calculator
Compute the Mach number from true airspeed and temperature.
- TAS from Mach Temperature Calculator
Convert a Mach number and outside air temperature to true airspeed via the local speed of sound.
- Calibrated Airspeed Calculator
Convert true airspeed back to calibrated airspeed using the two-percent-per-thousand-feet rule.