Reliance on a single nav source

GPS is the best navigation aid a private pilot has ever had, and trusting it completely is the fastest way to get lost — or to hit something while you're staring at it.

How the one source fails

A single navigation source is a single point of failure:

• GPS can drop out from a loss of receiver integrity (RAIM), interference or jamming, a stale database, or a dead battery in a handheld.
• VOR can be out of service, out of range (it's line-of-sight), or simply mis-tuned.

Picture it: twenty miles out, the GPS flashes a loss-of-integrity message and drops the moving map. If you've been watching only the magenta line, you now have no idea which of the three look-alike towns below you is the right one. If you've been ticking checkpoints on the paper chart all along, you already know — the failure is an annoyance, not an emergency.

Tablets add their own failure modes: a hot cockpit can overheat a tablet into shutdown on a summer afternoon, and a forgotten charge leaves you dark. Treat the electronic flight bag like any other single source — good until it isn't — and keep the backups physically available: a charged spare or a paper sectional folded to the current leg, and the nearest VOR already tuned and identified.

What cross-checking actually looks like

Cross-checking isn't a concept, it's a set of habits you run every leg:

• Keep the paper sectional out and folded to the current leg — not buried in the back seat.
• Verify the magenta line against the ground at every checkpoint — does the GPS position match what you actually see out the window?
• Note ETE and groundspeed for each leg even with the GPS doing the math, so a wrong number jumps out at you.
• Brief the next checkpoint before you reach the current one — stay ahead of the airplane.

Heads-down is eyes-inside

Here's the risk most pilots underrate: fixating on the GPS means your eyes are inside the cockpit, and in VFR that's exactly where mid-air collisions come from. A moving map you stare at is a collision hazard wearing a helpful disguise.

The fix is that the cross-check habit and the see-and-avoid habit are the same habit. And see-and-avoid is a method, not just good intentions: divide the windscreen into roughly 10° sectors, stop your eyes briefly on each — the eye can't detect traffic while it's sweeping — and spend most of your time outside, glancing in only for a few seconds at a time. The GPS check is one of those quick glances in, not a place to live. The look out the window that confirms your pilotage is the same look that clears you for traffic, so the pilot who navigates by looking outside is also the one least likely to hit anything.