With the below setup you can totally forget about switching timers and get accurate air time information at the end of a flight or at the end of a day.
All you need is two triggers to tell OpenTX when to activate (On) and when to deactivate (Off) the timer. Many triggers are imaginable. I used the following for pure gliders:
On Trigger: Moving rudder and aileron at the same time in any direction
Off Trigger: Vertical speed (TELEx:VSpd) is very small for at least 10 seconds
In this example, the off trigger needs a receiver with vario. However, it is possible to use other off-triggers (see below).
L25 is active if the rudder stick moves at the same time then…
L26 … the aileron stick
L27 is the actual timer switch. It is active (Sticky) if L25 is true. It is deactivated if L29 is true.
L28 checks if vertical speed is under a certain threshold. VSpd < 0.3m/s works for me.
L29 is active if L28 is true for at least 10 seconds
Alternative Off Trigger
It is possible to use a variety of triggers to switch the logical switch On or Off. Here is one more possibility. The timer switches off if the Ele(vator) has not moved for a certain time. The only change is that now…
… L28 checks if the Ele(vator) is moving
… L29 checks if L28 is true for at least 10 seconds
L27 triggers those timers you want to be running
Special Function (Optional)
This is mostly self-explanatory and nothing but a couple of special functions to announce timers being “on” or “off” and the optional switch to reset timer 1 (I also reset telemetry at the same time). I keep Timer 2 running to sum up the day and reset Timer 1 after each flight.