Safety notice
Please read this before you use JVFR in an aircraft.
JVFR is not certified and is not a primary source
JVFR is a hobby project, provided free and as-is, with no warranty of any kind. JVFR must not be used as your primary source for flight preparation or navigation. Always verify against official charts, official aeronautical information and an official weather briefing.
What that means in practice
The data is community-sourced
Airspaces, airfields and navaids come from openAIP, which is maintained by volunteers. It's good, but it is not an official AIP. It can be out of date, incomplete or wrong. Temporary restrictions in particular may not be represented at all.
Aviation data ages
Packages are rebuilt on the AIRAC cycle, but a package downloaded to your device stays as it was until you update it. The app flags a package as out of date when a newer cycle exists. Check that before you fly, not while you're flying.
Traffic is incomplete
The traffic display shows ADS-B and MLAT data from aggregator services. Aircraft without a transponder, aircraft outside receiver coverage, and anything the network has not picked up are simply absent. An empty screen does not mean an empty sky. It is not a collision avoidance system and must never be confused for one.
Warnings are advisory
The airspace proximity warning projects your current ground track forward. It cannot know your intentions, it depends on your device GPS, and it only considers airspace near your altitude. Treat it as a prompt to look, not as clearance or as a guarantee.
Performance figures are your figures
Mass & balance, fuel planning and the endurance rings are calculated from the aircraft profile you entered and a constant fuel burn. They do not know about your actual power setting, mixture, weight or the conditions on the day. Check the results against your POH and your own judgement. If you fill in that your piper archer burns only two gallons an hour, the app will take your word for it.
JVFR runs on a consumer device
Phones and tablets overheat, run out of battery, lose GPS lock, and receive updates that change behaviour without warning. Carry a means of navigation that does not depend on one.
In short
JVFR is built to make flight preparation more convenient and to improve your situational awareness. It is a very useful second opinion, but not a replacement for official sources. The pilot in command remains responsible for the flight, and that has not changed because an app is attached to your yoke.
Found something wrong in the data or the app? Please tell me: info@jvfr.net.