ADVANCED PILOT INSTRUMENT TIP THE LESSER-KNOWNS CAN YOU IDENTIFY THESE CHART SYMBOLS? BY IAN J. TWOMBLY 1 YOU STUDY THEM IN TRAINING and stare at them on every flight. Yet chances are there are more than a few symbols you don't understand. Aeronautical charts have a wealth of information-if you know what to look for. We're going to assume you have the basics of the instrument low altitude en route charts covered, so here are five symbols you may not know. 1 Minimum crossing or turning altitude. When a waypoint or navaid has a flag with an X inside, it indicates 2 3 AOPA.ORG/FT 51http://aopafinance.org/FIRSTTIMEBUYER http://www.AOPA.ORG/FT