The CoreLocation framework in iOS version 11.0.x has a new feature that limits the allowable distance an iOS device can travel in the 30 mins after Airplane Mode is enabled. This restriction expires after 30 minutes, and is based on the "last known position" of your iOS device at time Airplane Mode is enabled. If your aircraft travels faster than 300 knots and you exceed the allowable distance from the origin, it's possible you could lose the own-ship position indicator in your EFB app.
This issue is expected to be rare, especially for non-military pilots, but can affect all iOS 11 users with external GPS units from Bad Elf and other manufacturers. This includes accessories connected via Bluetooth, 30-pin Dock Connector, or Lightning port.
It is not known if this CoreLocation restriction applies to the internal GPS as well.
If you travel faster than 300kts away from last known position within 30 mins of enabling Airplane Mode you will lose the own-ship position indicator in your EFB app. Once 30 mins has passed, the own-ship GPS information will flow again.
Before or during your flight, perform the following steps to clear the cached Wi-Fi location information:
- Put your iOS device into Airplane Mode (Wi-Fi, Bluetooth, and Cellular OFF)
- Go to Settings.app > Privacy > Location Services and toggle Location Services OFF, then back ON.
- If needed, turn Bluetooth back ON to detect and connect to your Bad Elf GPS unit.
Alternatively, make sure to wait at least 30 minutes after enabling Airplane Mode before starting your flight.
This issue has been fixed in iOS 11.1 (released Oct 30, 2017). Users should upgrade from 11.0.x to 11.1 when possible.