How do I start the datalog recording before takeoff?

[Evan Schellenberg]

The datalog normally starts recording on fixed wing autopilots when the autopilot detects consistent GPS velocity values. On helicopter autopilots the datalog starts as soon as the autopilot becomes Ready.

We recommend setting the datalog to start recording before the takeoff command though, since there is often important flight data that should be recorded during the takeoff.

To start the datalog as soon as the autopilot initializes add the command "[recordHistory]=50" to your fly file before the takeoff command.

Here is an example of a fly file with this line correctly used:
metric
[recordHistory]=50  //Start recording the datalog as soon as the autopilot initializes
takeoff
climb   150
waitClimb 100
flyTo  ( 1000, 1000)
circuit (0, 0), 0, 0
repeat -1