ForeFlight’s latest update adds in-flight wake turbulence alerts for pilots with Pro Plus and Performance subscriptions while using a Sentry ADS-B In or FLARM device to provide traffic information. The Alerts show as ribbons depicted on the ForeFlight moving map as the user’s aircraft approaches the path of a wake turbulence-generating heavy airplane.
Audible and visual alerts warn the user about the potential for wake turbulence including distance to the possible encounter. The ribbon is split into cyan and red areas divided by a white line with chevrons showing where the user’s aircraft will intersect with the ribbon. The wake-causing airplane’s ID and relative altitude are also shown. The red portion of the ribbon indicates potential wake turbulence within 100 feet above and 300 feet below the user’s altitude, while the cyan portion indicates an altitude that poses no immediate danger.
A ForeFlight engineer who lost a friend in a wake turbulence accident was inspired to create the wake alerts feature, according to senior product manager Connor Hailey. The feature doesn’t work below 500 feet so alerts are not sent to pilots near the ground and busy with landing the aircraft.
A proprietary algorithm looks at the weight category of the turbulence-producing aircraft and it also takes into account winds aloft and the speed of the aircraft. To test the algorithm, ForeFlight has been collecting information by letting it run in the background on the ForeFlight Mobile app with the alerts switched off. In analyzing the data, ForeFlight was able to see some situations where users may have encountered wake turbulence, then it sent these users emails to ask if they had experienced wake turbulence in those specific instances. “This was to inform our confidence in the algorithm,” Hailey explained.
While wake encounters are rare, the information from the tests “gave us confidence in releasing the feature,” he said. In one case, a user flying behind a heavy airplane was given a “caution wake turbulence” call by an air traffic controller and the pilot avoided any wake turbulence based on that call. When ForeFlight engineers looked at the data, they could see the user’s airplane crossing at the same altitude as a heavy Boeing, and in this case the potential wake turbulence would have generated an alert in ForeFlight.
ForeFlight also tested the wake turbulence feature in simulators, before the test campaign with user data.
The new wake turbulence alerting works anywhere in the world as long as ForeFlight can identify the user’s aircraft via ADS-B Out and has a source of real-time traffic information. “There is no technical limitation beyond that,” Hailey said. It also works with FLARM (flight and alarm) systems used by light aircraft flying in European and UK airspace.