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Watch the waypoints: one of the rules of GPS IFR is to check your waypoints after you load them up to make sure you didn't spell something wrong. But that assumes you read the chart right.

Why is it that the likelihood of doing something embarrassing is directly proportional to how many people are going to see you do it? A couple issues ago, I put some of my favorite tips for using your GPS in lieu of VOR navigation into a video and tossed it up on YouTube. The video was fine and the tips were sound, but I let one not-so-trivial mistake sneak in.

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I'd like to think that I wouldn't let such an error sneak by in an actual airplane, but I've seen myself and others do some pretty myopic, bone-headed things with cockpit avionics. Hopefully if it did really happen, the worst fallout would be a verbal censure from ATC or even a letter from the FAA because I (unintentionally) deviated from a clearance.

The worse consequence in the real world, of course, would be broadsiding a mountain.

Airways to Flightplans

As anyone who's used a typical GPS in IFR knows, clearances are given by Victor airways, but those airways usually must be entered into the GPS as VORs and intersections. (You GNS 480 and G1000 users can stop snickering now.) That usually means running your finger along the chart, picking out the way-points and entering them one by one.

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That kind of manual entry is ripe for operator error. It's actually surprising to me how rarely we enter one of these waypoints wrong, but it does happen sometimes. The plus side is that when the error is due to misspelling, the resulting route is so bizarre--your ETA is suddenly 23 hours into the future--that we catch it right away.

But a more subtle error is entering a waypoint close to (but not at) the next waypoint in the plan. This happened when I was describing a flight in that video from Boeing Field in Seattle that intercepted and flew V2. I had done this flight countless times in the real world, so I just looked quickly at the chart and saw that V2 ran from SEA to YKM, the Yakima VOR.

Except that it doesn't. The airway runs SEA-ELN-YKM. At ELN, the Ellensburg VOR, V2 has a dogleg. It's V4 that goes directly between SEA and YKM. That's also a route I'd flown many times. Of course, I'd have flown V4 higher since the MEA is 10,000 feet rather than 8000 on V2. Oops.

My excuse is speed and carelessness in that it wasn't a real flight and that the destination VOR for both airways is on the other side of the chart. I didn't flip it over, relying on the distance markers for the airway. Bad editor, no donut.

Is this likely to happen to you? Not unless you're recording yourself doing it and posting it for millions of people to see. But it's a good reminder that GPS navigators follow the "garbage-in, garbage-out" rule and you should make sure any change to your flight plan makes sense before you let the box guide you. Check out the sidebar on page 14 about AirwayPlanner to see one company's effort to ease this burden.

Checking your waypoints is also a healthy habit when loading approaches. Read over the waypoints that load to ensure you loaded the right approach. I once thought I loaded a GPS for Runway 7 but had really loaded the approach for Runway 25. The map view of the approach that pops up when you load it looked right at a glance because the two approaches are basically mirror images of each other. It wasn't until I cross-referenced the waypoint that I saw they were backwards--what I expected as the IAF was the missed-approach holding point--that I realized what I had done. But there was plenty of time to reload it and start again.

Maybe this mis-entering thing is just a problem I have. But if you do share this failing, rest assured you're not the only one who needs to proofread.

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Jeff Van West tries to proofread his flightplans and his articles, but he still needs help.
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Title Annotation:CHART CLINIC; global positioning system instrument flight rule
Author:West, Jeff Van
Publication:IFR
Geographic Code:1USA
Date:Sep 1, 2010
Words:771
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