You have to fly it a few times and get an idea. The 9C has 3 timers on it. I have the first set to total transmitter time since charge, second to time on since I hit the switch and third is time on when throttle higher than a quarter. Course, you can't seen any of them when you are flyin so it really doesn't matter. I also just look at the tank once in a while. Flew without a header for years. I have one now though. Nice for aerobatics.