TAT / SAT & Ram Rise Calculator (Mach)
Total vs static air temperature: compute the ram rise your temperature probe feels at speed, and recover true OAT from an uncorrected gauge.
At M0.78 the ram rise is ~26 °C: air brought to rest against the probe converts its kinetic energy to heat. Anti-ice logic, engine settings and TAS computations all live or die on doing this correction in the right direction.
Formula
⚠️ For flight planning and education only — verify with your POH/AFM, certified instruments and official sources. Not for primary navigation or airworthiness decisions.
Total vs static air temperature: compute the ram rise your temperature probe feels at speed, and recover true OAT from an uncorrected gauge.
About TAT / SAT & Ram Rise Calculator (Mach)
An airliner's temperature probe at cruise reads nearly 30 degrees warmer than the air it flies through — not an error, but physics: air stagnating against the sensor converts kinetic energy to heat, the 'ram rise.' This calculator runs the total-temperature relation both ways for any Mach and probe recovery factor, separating TAT (what's measured) from SAT (what's true) — the correction beneath icing predictions, engine ratings and every TAS readout.
How to use TAT / SAT & Ram Rise Calculator (Mach)
- 1Enter — sensible defaults are pre-filled so you see a worked result immediately.
- 2Read the live results: .
- 3Check the "With your numbers" line to see the formula TAT = SAT × (1 + 0.2·k·M²) (kelvins); ram rise = TAT − SAT substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use TAT / SAT & Ram Rise Calculator (Mach)?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula TAT = SAT × (1 + 0.2·k·M²) (kelvins); ram rise = TAT − SAT with sources cited on the page
- ✓At M0.78 the ram rise is ~26 °C: air brought to rest against the probe converts its kinetic energy to heat. Anti-ice logic, engine settings and TAS computations all live or die on doing this correction in the right direction.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
What's the difference between TAT and SAT?+
SAT (static air temperature) is the actual temperature of the undisturbed air — the meteorological truth. TAT (total air temperature) is what a probe moving through it measures after the air compresses to rest against the sensor, warmer by the ram rise 0.2·k·M² in kelvin terms. At M0.8 that's 26–28 °C; at GA speeds under M0.2, under 2 °C.
Why does icing assessment use TAT in jets?+
Because the airframe's leading edges feel stagnation temperature, not static: a wing at M0.78 in −30 °C SAT air has surfaces near −4 °C — inside the icing band when the SAT alone suggests safety from it. Engine anti-ice procedures keyed to TAT thresholds (commonly +10 °C TAT in visible moisture) encode exactly this.
What is the recovery factor k?+
The fraction of the full theoretical ram rise a real probe captures — ideal stagnation gives k = 1.0, and modern heated TAT probes achieve 0.97–1.0. Flush-mounted or poorly placed GA probes recover 0.7–0.9, reading somewhere between SAT and TAT. Your aircraft's k (from the POH or probe spec) makes this correction exact.
Does my 120-knot trainer need to care?+
Barely — at M0.18 the full ram rise is about 1.9 °C and a typical GA probe shows perhaps 1.4 of them. That's inside gauge tolerance, which is why PHAK barely mentions it. It starts mattering above ~250 KTAS, and by turboprop cruise speeds the correction is the difference between right and wrong TAS.
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