PLT165: Altimeter
What code PLT165 covers, why the FAA tests it, and how to study Altimeter before your checkride.
Recall altimeter - effect of temperature changes
What this means for your checkride
A pressure altimeter assumes standard temperature. When the air is colder than standard, it is denser, so pressure levels sit lower than the instrument assumes and the altimeter reads higher than your true altitude. Warmer-than-standard air does the reverse.
Temperature error is a real terrain-clearance hazard on cold days, so the FAA tests the rule that from a cold source you fly lower than indicated, and whether you know to add a correction over high terrain.
The memory aid people get backwards: high to low, or hot to cold, look out below. Flying toward colder air without correcting means your true altitude is lower than the altimeter shows.
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.