Flying with ForeFlight and iOS 5

November 30, 2011 Update – ForeFlight Mobile 4.3.1 is available for download and addresses this issue.  Apple added a new flag in iOS 5.0.1 to let apps mark data as “never delete”.  With ForeFlight Mobile 4.3.1 and iOS 5.0.1, chart and plate data cannot be removed from inside the app.  We still recommend that all pilots pre-flight their apps before every takeoff.


Original post:

Earlier this week, Apple released iOS 5 – a big update to the operating system for the iPad and iPhone. We have been testing ForeFlight Mobile for the last few months using pre-release versions of iOS 5. If you’re running our latest version, 4.1.1, you should not see any bugs in ForeFlight that are related to iOS 5. However, read on for important information about a change in iOS 5 that will impact how you use aviation apps.

Upgrading to iOS 5

Any time you upgrade to a new version of iOS, there’s the possibility that apps could get deleted off your iPad or iPhone. Additionally, data inside apps can get deleted in certain circumstances – called “cleaning”. After you upgrade, please follow the instructions below on Preflighting your apps. The likelihood of you hitting this issue is low, but being aware of how cleaning gets triggered will help you steer clear of turbulence.

Data Removal in iOS 5

Once you are running iOS 5 on your iPad, you need to be aware of an important change that Apple made. This will impact how you fly with your iPad, whether you’re using ForeFlight Mobile or any other aviation app.

If you are downloading large files and your iPad or iPhone is running low on disk space, iOS 5 can remove data from inside apps under certain conditions. For example, if you had 1GB of free space and downloaded a 3GB movie, the operating system will delete 2GB of data from other apps to make room. When this happens, your iPad home screen with display a “Cleaning” message underneath app icons that are having data removed. The next time you start those apps, they will be missing data that had been previously downloaded.

Apps can store a limited amount of data in a Documents directory that never gets deleted, but apps that store a large amount of data – like aviation apps with downloaded plates and charts – must store downloaded files in a Caches directory that can have data removed from inside of it.

Every time you start ForeFlight Mobile, we run a data integrity check inside the app to make sure all of the data is still present.  If iOS 5 deletes any downloaded data from ForeFlight, we display a message that informs you that data has been deleted and you need to visit the Downloads view to re-download.  This message displays about 10-15 seconds after you have started the app.  If you see this message, go to Downloads and tap the green Download button to re-download any missing information.

We have submitted a report to Apple requesting an enhancement to store data in an area that will not be cleaned. In the meantime, here are our recommendations for flying with iOS 5:

  • Leave extra space on your iPad.  iOS 5 only deletes data as a last resort if you are downloading or creating things inside another app and have no available space on your iPad. Leaving a few gigabytes of free space and not filling up your iPad will prevent this from happening.  You can check available space in the Settings app by tapping on General -> About.  Free space is listed in the ‘Available’ row.
  • Disable cellular radios before flight.  Before taking off, disable the cellular and WiFi radios in your iPad by setting WiFi to OFF and Cellular Data to OFF.  (We cover how to do this in our iPad Proficiency Video.)  Since there is no reliable Internet available at altitude, we always recommend turning off radios before a flight.  However, it is especially important in iOS 5, since your iPad only removes data from apps if it is downloading something, and you can’t be downloading if you’re not connected to the Internet.
  • Preflight your apps. After you disable cellular radios, open up the apps you’ll be flying with and make sure you have the necessary data downloaded for your flight.  If you are flying with ForeFlight Mobile, follow these 3 steps:1. Tap on Downloads and ensure there is a green check next to the correct states for each data type (Terminal Procedures, VFR Charts, etc).2. Tap on Airports and view each airport on your route.  Make sure the airport information at the top displays correctly, then check to make sure all of the procedures have a green “Saved” label.  If the procedures have a gray “Unsaved” label, then they are not saved to your iPad and will not be available for in-flight viewing.3. Tap on Maps and pan through all of the VFR Sectionals and IFR Enroutes in the area you will be flying.  Some of the higher level detail is cached by the mapping engine, so make sure to zoom into the highest level of airport detail.  If you see a gray grid after zooming in, then the chart data is not saved to your iPad.

    If any data is missing in steps 1-3, turn WiFi or 3G back on, then visit Downloads inside ForeFlight to download the necessary data to your iPad. Missing data could be the result of iOS 5 deleting data you already had. It could also happen if you had not selected the necessary data types and states in download settings, or had forgotten to download all of your data.

If you are using other aviation apps, please contact the vendor and ask for instructions on pre-flighting.

If you have any questions, please send us an email at team@foreflight.com.