Let’s say that you’re going on a 300 nm (550 km) flight — a typical distance for a cross-country trip in a small plane — VFR, without radar coverage.  You file a flight plan, take off on time, but don’t arrive at your destination.  A couple of hours after your planned arrival time, once flight services has completed a few phone calls (your destination airport, your cell phone, your emergency contact) and confirmed that you haven’t landed safely and forgotten to close your flight plan, a formal search begins.

Where do they look?

Point A to Point B

Let’s say that you filed your flight plan from Point A to Point B and that there are no obvious barriers (mountains, large bodies of water, restricted airspace).  I’m not sure exactly how SAR works, but let’s assume that they’ll search within a 5 nm radius of each airport, and along your route of flight from those circles, allowing for a 10° drift in either direction.  The search area appears in grey below (not to scale):

Point A to Point B search area.

For a 300 nm flight, using my very rusty high school geometry skills, I calculate the search area to be nearly 9,500 nm²!  That’s a lot of forest to search for a little plane with an unconscious pilot strapped into the front seat.

Point A to Point B (via Point C)

Fortunately, we can improve our chances quite a bit, simply by providing a checkpoint halfway through the flight:

Point A to Point B via Point C search area.

Now that Search and Rescue knows that you intended to fly via Point C (represented by the yellow triangle), rather than, say, flying to the north for better scenery, or to the south to buzz your buddy’s cottage, they can anchor their drift lines at an additional point, cutting out a lot of search area (I’m still allowing a 5 nm circle of ambiguity around the checkpoint).  I calculate that the search area is now reduced from nearly 9,500 nm² to just under 5,500 nm², a reduction of over 40% simply by adding one checkpoint in the flight plan.

Point C to Point B

But wait, there’s more!  Let’s say that, when you were over Point C (your midway checkpoint), you actually made a call to flight services and gave a position report.  Now there’s no need to search anything before Point C, because they know you passed it before you made your forced landing:

Search area after making a radio call over Point C.

You’ve reduced the search area from the original 9,500 nm² down to about 2,800 nm² — still a lot, but I’d bet more on your chances now.  Simply choosing a checkpoint, and making a radio call over it, can make a huge difference.

Caveats, etc.

Flight following is an even better option, since ATC will know much more precisely where you disappeared from the radar.  Unfortunately, flight following at lower altitudes is available only in highly populated areas.  In Canada,  below 10,000 ft you’re beyond radar coverage for much of the southern area of the country, not to mention the vast north.  Even in the US, radar coverage can be spotty — I’ve fallen below radar at 7,000 ft when flying IFR in both Maine and New Hampshire, for example, reverting to non-radar reporting procedures.

A checkpoint makes sense only if you can report over it, which means that you need to be able to reach flight services, which is non-trivial at low altitudes away from populated areas.  I plan my VFR flights with checkpoints that I know will be in range of an RCO or DRCO; if that doesn’t work, you can always try relaying your position report through another aircraft (air-to-air range is much further than air-to-ground).

Another interesting option for people who fly a lot in remote areas is the Spot personal messenger (site), which updates your position continuously via GPS and satellite and displays it on a web site. I haven’t tried it yet, but the price looks reasonable. It would be critical to mention the Spot in the remarks for your VFR flight plan, so that SAR would know to go to the site and check your flight path.