Safety and failsafe
The failsafe is the part of the setup nobody tests and everybody needs. Set it before the first arm, and test it on the bench with the props off before you test it in the air.
The checks that belong before first arm
Motor order and direction with the props off. Board alignment confirmed by tilting the aircraft and watching the horizon in the configurator. Failsafe set to Stage 2 with a delay that matches the aircraft weight. Battery profile set to the exact cell count and capacity, never auto. A range check in reduced power mode. Every one of these takes under a minute and covers almost every first-flight failure.
Stage 2 with the right delay
A delay that is too short drops the aircraft on a momentary dropout; too long and the aircraft flies on after the link is gone. As a working rule: 0.2 to 0.3 seconds on a whoop or a ducted indoor build, 0.3 to 0.4 seconds on a 5-inch, 0.5 to 0.6 seconds on anything above 1 kg that carries a payload. Stage 1 failsafe, which just cuts the throttle, should not be used: it leaves the aircraft armed and falling.
GPS rescue is a last resort, not a feature
Rescue only helps if the satellite count is honest and the pack has the reserve to climb. Set the minimum satellites to 8 for a 4-inch and 9 or 10 for anything flying past 3 km, because a rescue triggered on a poor fix will fly confidently in the wrong direction. Test it deliberately at close range before trusting it far away, and remember that a rescue climb can draw twice the cruise current.
Where and when
Nothing on this site is a statement about where you are allowed to fly. Rules on registration weight thresholds, remote identification, altitude limits, flight over people and radio licensing differ by country and change over time. Check the rules that apply where you fly, and check them again when the aircraft changes weight — a 246 g build that gains a camera is a different category of aircraft in most places.
Failsafe settings on file
| Airframe | All-up weight | Failsafe | Link |
|---|---|---|---|
| 5in-freestyle-baseline | 682 g | Stage 2 · 0.4 s delay · no GPS rescue | ExpressLRS 2.4 GHz · 250 Hz |
| 7in-longrange-cruiser | 1042 g | Stage 2 · 0.6 s delay · GPS rescue on, 12 s hover | ExpressLRS 915 MHz · 100 Hz |
| 3in-cinewhoop-ducted | 318 g | Stage 2 · 0.3 s delay · no rescue | ExpressLRS 2.4 GHz · 150 Hz |
| 65mm-whoop-indoor | 29 g | Stage 2 · 0.2 s delay · drop | ExpressLRS 2.4 GHz · 50 Hz |
| 5in-racing-lowslung | 524 g | Stage 2 · 0.25 s delay · drop with turtle mode armed | ExpressLRS 2.4 GHz · 500 Hz |
| 4in-sub250-longrange | 246 g | Stage 2 · 0.5 s delay · GPS rescue on, 9 s hover | ExpressLRS 915 MHz · 100 Hz |