PLT175: Autorotation
What code PLT175 covers, why the FAA tests it, and how to study Autorotation before your checkride.
Recall autorotation
What this means for your checkride
In autorotation the engine is disconnected from the main rotor and upward airflow through the descending rotor keeps the blades turning. Each blade is divided into a driven region near the tip that produces drag and slows the blade, a driving region in the middle that produces the force to keep the rotor spinning, and a stall region near the root. The pilot adjusts collective to balance these regions and hold rotor rpm within limits. Prior to touchdown the pilot flares with aft cyclic to decelerate, which changes the airflow and increases rpm.
Autorotation is the primary response to a power loss, and understanding the blade regions explains how rpm is controlled during descent and flare.
Pilots sometimes think raising collective adds rpm; in fact raising collective enlarges the driven and stall regions and reduces autorotative rpm.
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.