PLT017: Lift-to-Drag Ratio
What code PLT017 covers, why the FAA tests it, and how to study Lift-to-Drag Ratio before your checkride.
Calculate L/D ratio
What this means for your checkride
The lift-to-drag ratio measures aerodynamic efficiency: how much lift the wing makes for a given amount of drag. It peaks at one angle of attack, and the speed that flies that angle gives the best glide and the most efficient range.
Maximum L/D sets the best-glide speed and efficient cruise, so the FAA tests what it represents and why best-glide speed matters after an engine failure.
Pilots think best glide means the slowest speed. Best glide flies the maximum L/D angle of attack; slower than that increases drag and steepens the descent.
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.