I have Aeroplane Heaven's Bristol Bulldog where compressed-air engine start is modeled (somewhat?).

The manual is not very comprehensive though, and I wonder how this worked IRL.

What I could figure out so far is the following:

There is a special small tank ('starter carburetor'?) containing a small amount of fuel into which air is compressed. By using tens of strokes with a 'primer'? The compressed air evaporates the fuel. The magnetos are turned on, as is a special 'starter magneto'. Then a crank in the cockpit is turned several times, probably to build up electricity in the starter magneto. Finally a starter button is hold down until the engine starts.

Any knowlegable person here to correct the above and fill in the blanks? I do not understand what the starter magneto actually does, is it connected to a special spark plug? How/when is the evaporated fuel moved from the pressure tank to the cylinders? What does the starter button do? As far as I can see the prop is not rotated in the process, how can all this work?

Thanks a lot!

 

 

I think this is proper.
The starter magneto is no more than a generator supplying high voltage to the engine magnetos so when the engine is turned over, IE low RPM, there is a hot spark.
The starter magneto switch connects the starter magneto to the engine magnetos.
The crank in the cockpit is connected to the starter magneto itself, usually by a chain drive and gearing so that the starter magneto spins at 4:1. Internally, in the magneto, is more gearing at 5:1. The end result is at about 1.5 cranks per second the starter magneto armature spins at ~2300 rpm, plenty to create high voltage.