PLT032: Mach Speed Regimes
What code PLT032 covers, why the FAA tests it, and how to study Mach Speed Regimes before your checkride.
Define MACH speed regimes
What this means for your checkride
Mach number is true airspeed divided by the local speed of sound. The regimes are subsonic, transonic, supersonic, and hypersonic. Light airplanes stay well subsonic, but high-altitude and jet operations track Mach because the critical Mach number, where airflow first reaches the speed of sound over the wing, limits how fast they can safely fly.
At altitude Mach, not indicated airspeed, sets the high-speed limit, so the FAA tests the regimes and why Mach matters more than IAS up high.
Pilots think the speed of sound is fixed. It falls as temperature drops with altitude, so the same true airspeed is a higher Mach number in the colder air aloft.
Where to study it
A code on your test report is an area of deficiency. An authorized instructor must review it with you and endorse that review before you take the practical test, and the examiner may revisit it during the oral. Study it until you can explain it out loud, not just recognize the answer.