Inertial is in development and is not yet available. This page describes what it is being built to do. The navigation code is not finished, nothing here has been measured on real flights, and there is no release on Google Play yet. Everything below is design intent, not a description of a shipping product.
Inertial is an inertial flight recorder for the cockpit of a light aircraft. The problem it is built for: when the satellite signal is jammed, denied or simply weak, a recorder should go on estimating where the aircraft is — from the phone's own motion sensors and a physical model of how the aircraft flies.
GNSS jamming and interference have become ordinary over large parts of the world, and they rarely present as a clean outage. They present as a track with a hole in it, or as a track with a confident and wrong section — discovered on the ground, after the flight, when nothing can be done about it.
Mount the phone as you normally would. Inertial reads the satellite receiver and, at the same time, the phone's own motion sensors — the accelerometer, the gyroscope, the magnetometer, and the barometer on devices that have one. When the satellite signal degrades or disappears, the estimate carries on from motion alone.
It works in two tenses:
Dead reckoning from a phone's sensors alone drifts, and it drifts quickly. What makes it useful is knowing how the aircraft moves, so Inertial is designed to apply the strongest model it has for the type being flown:
You tell the app what you fly, once.
No account. No sign-in. No server. No advertising. Your flights are written to your phone and stay there until you choose to export or delete them. Inertial sends nothing anywhere, which is a design decision rather than a setting you have to go and find.
Recordings export as IGC and KML through the Android share sheet, for your usual flight analysis.
Inertial is not a certified navigation instrument, and it is not for flying by. It gives no steering guidance, no airspace, no final glide and no traffic, and it must not be used to navigate an emergency. It does not replace your logger where an approved logger is required. It is a recorder and a track reconstructor, to be read after the flight. Fly the aircraft on your certified instruments.
Still in development, as the notice at the top says. It will be a one-time purchase, with no subscription and no in-app advertising.
No performance figure appears anywhere on this site, and none will until it has been measured on real flights. Dead reckoning from a phone's sensors is easy to demonstrate badly and hard to do well, and a number quoted from a simulation is not evidence about your aircraft.
If you fly and would like to hear when it is available, write to support@flyinertial.com.