PLT054: Reading The Glider Polar
What code PLT054 covers, why the FAA tests it, and how to study Reading The Glider Polar before your checkride.
Interpret information on a Glider Performance Graph
What this means for your checkride
The glider polar is a graph that plots sink rate on the vertical axis against airspeed on the horizontal axis, using the same speed units. The peak of the curve marks the minimum sink speed and the lowest sink rate, and a tangent drawn from the origin to the polar identifies the best glide, or best L/D, speed. Dividing the best L/D speed by the sink rate at that speed gives the glide ratio in calm air. By shifting where the tangent touches the curve, the pilot reads the faster speed to fly for a headwind or for air that is sinking between thermals.
Reading a polar correctly is how a pilot selects minimum sink, best glide, and speed to fly, so interpreting the graph appears directly on the knowledge test.
Best glide speed is not the same as minimum sink speed. Minimum sink is the slower speed that loses the least altitude over time, while best glide loses the least altitude over distance.
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.