An iPad personal electronic device; not inflight certified; was used for VFR navigation and about two hours into the flight at 10;500 FT overheated and shutdown.

Narrative

While on an cross-country/sightseeing flight; I was using an iPad to display sectional charts for navigation. The same software can also display instrument charts and approach procedures; with an overlay of the GPS-derived position. The software's authors do not recommend it for use for navigation; but pilots may do so anyway: FAR 91.103 requires only that 'Each pilot in command shall; before beginning a flight; become familiar with all available information concerning that flight.' During cruise approximately two hours into the flight; the iPad displayed a notice indicating that it had overheated; and shut down within about five seconds. I had paper charts available and used them to continue the flight; though it took a couple of minutes to find the correct position on the chart and fold it appropriately. Had this happened during a complicated instrument approach; especially without paper charts both available; safety could have been impacted. Although the temperature in the cockpit was quite comfortable; it was a sunny day; research indicates that the large screen of the iPad acts thermally like a black surface; so considerable heat can be absorbed from the direct sunlight. The reduced air density at 10;500 FT may have impacted heat rejection. Certified electronic flight bags are presumably designed for a wider range of cockpit environments than much cheaper consumer products like the iPad; pilots are encouraged not to rely on such consumer devices; but I think this particular failure should be more widely communicated. Despite being a professional electrical engineer; I certainly did not anticipate it.