Many GPS and MFD displays are too crummy to be of any real use in avoiding
airspace. The Bendix-King displays are among the worst. Even the color MFD
display is only half VGA quality and uses magenta lines for everything from
depicting airspace to the flight planned route. It is very easy to mistake
an airspace line for something else with this unit. Also, most displays
cannot draw curved lines very well, so when you zoom into a lot of class B
you discover that instead of a circle it is a complex polygon.

I think the biggest troublemaker is the 'nearest' function on most GPS
units. The pilot punches in 'nearest' thinking that is the airport he wants
to go to when in fact the GPS selects some other waypoint. The pilot is busy
and does not do a good job of checking.

Another troublemaker is the flight plan route function. The pilot either
leaves out an intermediate waypoint or enters an incorrect one with the same
or a similar identifier, then follows the courseline right into airspace
where he does not belong. Another problem is not clearing out an old flight
plan before entering a new one. This is especially common on GPS units like
the King KLN 94. A pilot will select direct to an airport without clearing
the flight plan entered in a previous flight. When he wants to fly an
approach, he presses PROC, selects the approach, and appends it to the old
flight plan. Then he does not activate the approach and the next thing you
know he has wandered off 180 degrees from where he should be.

Getting confused on whether the CDI is displaying NAV or GPS information is
another source of trouble.

Pilots also blunder into airspace because they are fooling around with the
GPS instead of paying attention to what they are doing. They are
particularly likely to do this if the GPS goes off line for some reason. It
is an especially serious problem with handheld GPS.

Then there are outright database errors. Jeppesen mis-plotted some class B
airspace a few months ago and someone posted just recently that Jeppesen
missed that the Savannah VOR had been moved.

Of course, most airspace violations are of things like the Washington ADIZ
and TFRs, which are not in most GPS databases, depicted on any charts, or
otherwise easily accessible. In fact, even the FAA is unable to plot many of
these TFRs accurately. Many TFRs give as their center both a lat/long and a
radial/DME, which may be a mile or more apart -- this is a big deal when you
consider that a TFR may be only three miles in radius. Additionally, TFRs
may change size, shape and duration with little or no notice, long after the
pilot has taken off. The best navigation techniques in the world will not
help you with that.

The fundamental problem that I see the most is that pilots just get behind
the airplane. Instead of setting up the GPS in advance, they wait until the
last minute, attempting to do things like set up an approach as they enter
the final approach course. It gets pretty wild watching students do that.
Then they panic, wander off course, and get into airspace.

I do not claim to have made all these mistakes myself, of course.