Can only speak for the Garmin 430, since that's the only GPS I've used, but yes, that's basically it.
Press the "Direct" button. Then enter the ICAO code for your new destination. If you don't know the ICAO code, you can enter the airport name, as long as you don't mind having your head inside the aircraft for long enough to do that. And if you're trying to find a certain airfield just north of where I fly from, it might take a couple of attempts before you realise it's in the database as "Booker" and not "Wycombe".
After that, you'll be shown your track on the moving map, as well as a heading to fly. There's no wind correction though, you'll need to do that yourself. If the direct track takes you through any controlled or restricted airspace, it should be obvious from the moving map - although there are errors in the database, so best to check with your chart anyway. And it certainly won't show any TRAs.
If you can't fly direct, for whatever reason, it probably becomes far too complex to do in the air. You can certainly program in a multi-leg course with waypoints, but the chances of the waypoint you need being in the database are fairly slim, so you'd need to find the long/lat of your turning point, or else find it's radial and distance from a VOR, and program in a user way-point. Fine if you're doing it on the ground as part of your pre-flight, but I definitely wouldn't do it for a diversion.
The 430 has a very nice feature whereby once you've programmed in the destination airfield, you can pull up a list of all the frequencies for that airfield, and tune your radio into the frequency with a couple of button-presses. That might be enough that you don't need to pull out your Pooleys if it's a field you're familiar with, but if it's an unfamiliar field I'd still like to check the Pooleys for any local information.
I've said before on this forum that I'm not a huge fan of GPS. But, if I had to divert and I was in a GPS-fitted aircraft, I would certainly make good use of whatever features I could. At the very least, with the 430, this would be using the moving map to provide a visual clue as to where the airfield is. At best, I might use the Direct feature and the frequency list. I wouldn't rely purely on the GPS for the reasons listed above, but it can be a big help in reducing the workload at a very stressful time.
I'd imagine, having never used one in anger, that a GPS without moving map would be less use, but still helpful - it would provide a heading for you to fly, but without the visual clues it would take more brain-power, you'd certainly need to draw the course on a chart to check for controlled airspace, and if you can't fly direct it would be practically useless until after your last turning point. I'd guess.
Hope that helps!
FFF
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