Those who use iPads for charts and approach plates are advised to pre-flight their devices before counting on them for navigation, thanks to Apple's latest operating system upgrade. iOS5 includes a file-management feature that might be handy if you're downloading a movie, but could be inconvenient at the very least if it messes with your navigation-app data bases. In an explanation on its website, flight-planning app provider ForeFlight says iOS5 will randomly delete data to make room for new files and that could include your charts and approach plates. The iPad does display a "cleaning" symbol by the app icon that it's busily deleting data from but that can be easy to miss. ForeFlight recommends several strategies to keep you from discovering that the latest Transformers has pre-empted the information you now need for your flight.
The most obvious suggestion is to simply check that everything is as it should be before you leave. ForeFlight has built a feature into its app that checks to ensure the full data package is in place, but the operator does have to initiate that process and its best done on the ground. To prevent data from being deleted in flight, ForeFlight recommends shutting off the WiFi and 3G before takeoff. Keeping plenty of disc space available in the device will also prevent the problem from occurring in the first place.