PLT062: Stability Indices and the Lifted Index
What code PLT062 covers, why the FAA tests it, and how to study Stability Indices and the Lifted Index before your checkride.
Interpret information on a Pseudo-Adiabatic Chart / K Index / Lifted Index
What this means for your checkride
Stability indices summarize how likely the atmosphere is to produce convection. The lifted index compares a parcel lifted to a level aloft with the surrounding air: a negative value means the parcel is warmer than its surroundings and the air is unstable, favoring thunderstorms, while a positive value indicates stability.
Stability indices help forecast thunderstorm potential, so the FAA tests interpreting the lifted index and what its sign indicates.
A negative lifted index is the unstable, thunderstorm-favorable case; students often reverse the sign and read negative as stable.
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.