Recognize signal flags & failures

A navigation needle that looks confident and is wrong will fly you into a mountain very politely. The skill in this element is knowing exactly when to stop believing it.

The warnings

• OFF / NAV flag — the receiver is telling you the signal is unusable. The needle means nothing until the flag clears, so don't chase it.
• Loss of the Morse ident — if you can't hear the identifier, the station may be down for maintenance. No ident, no navigation.
• An erratic or full-scale CDI that won't settle — out of range, interference, or a failed receiver. Treat it as no information rather than bad information, and switch to another source.

The habit that ties these together: glance at the flag and listen for the ident before you trust a needle, not after it has already led you astray. Picture it mid-track — you're holding the 090 radial, needle centered, and the NAV flag drops into view. The needle is now meaningless: stop steering to it immediately, cross-check your GPS or pilotage, and re-establish on a source you trust before you correct toward anything. The danger isn't the failure itself; it's the second or two of habit where you keep chasing a dead needle.

GPS failures look different. Instead of a flag you get a loss-of-integrity message, a "DR mode" (dead-reckoning) annunciation, or the position simply freezing. In an urban canyon or deep valley a handheld can lose enough satellites to degrade silently — so a GPS that suddenly goes too steady, with no expected movement, earns a glance at the satellite-status page.

Station and waypoint passage

• The clean signal that you've crossed a VOR is the first positive, complete TO→FROM flip of the flag.
• Right over the station you fly through the cone of confusion — the flag flickers and the needle swings for a few seconds. That's normal passage, not a failure; let it settle and resume tracking on the far side.
• A GPS announces waypoint passage and sequences the next leg on its own — but confirm it actually sequenced rather than holding on the old fix, especially if you're hand-loading a route.