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.
Solve approximate constant-CAS TAS = constant-Mach TAS 1Inputs 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.
Assumptions and limitations
The compact equations are an approximation and do not replace the aircraft climb schedule, compressible-air data, operating limits, or flight-management computation.
References
-
AC 25.1581-1: Airplane Flight Manual — Federal Aviation Administration