the cylinder temperature has to be minimum 200° !!!
gauges are over the fuelcock levers, look over your right shoulder.
That take a lot of time.....in singleplay you can use the speed up function.
If the engines are at that temperature, all works like a charm . But dont forget to check the ruder trimm, its 'off' by default
as you have only two propeller settings (0-4% is coarse, from 5% to 100% its fine pitch) dont give too much power during start to avoid overrev. And disable the carburetor heating, you need it to start the engines, but it reduces the power.
during flight, i always stay at fine pitch. rpm 2000to 2200. And if your engines begins to stutter, try if to enable the carb heating helps (it does in most cases)
The game lacks of documentation, true. As you are wondering very often "has this to be this way or is it a bug"
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