What is the little valve/device that I see pilots holding at start-up? It has a tube running into the turbine and the operator appears to turning something.
Like Tor said that's the propane/butane gas valve on the external cylinder of starting gas. Most gas start engines use a mix of propane & butane as the starting gas.
Even with a full auto start engine some flyers still start from the external cylinder. You save a little weight & space by leaving it out of the model & if it all goes horribly wrong it's one less thing to explode! - John.