PLT087: Course and DME Indicator
What code PLT087 covers, why the FAA tests it, and how to study Course and DME Indicator before your checkride.
Interpret readings on an Aircraft Course and DME Indicator
What this means for your checkride
A course indicator such as the HSI shows aircraft position relative to a selected course: the course-indicating arrow is set with the course select knob, and the course deviation bar shows left or right deviation from that course. Distance measuring equipment (DME) adds slant-range distance to or from the station, converting the interrogation timing into nautical miles on the mileage readout. Read the two together to know both your angular position on course and your distance from the facility.
Combining course deviation with a DME distance readout is how you fix position and fly arcs or fixes off a VOR/DME.
DME shows slant range, not ground distance, so directly over a high station the readout reflects altitude rather than horizontal 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.