The valve you see in the videos is a gas valve that opens up for the butane/propane gas mix that is used
on many turbines to start the heating process and reach a temperature that is high enough to ignite the
kerosine. This is slowly being replaced by the fully automatic kerostart where - as you say - you simply
throttle up and down once, after that the entire start-up is controlled by the ECU and goes through the
heating (obtained by the igniting of a kerosine mist and a heater plug) to the ignition of the regular kero
fuel, throttle up to idle, calibrating at a higher rpm before settling at idle again. At this point the control of
the turbine is turned over to the pilot and the plane is ready to roll out. Most turbines are sold with a manual
or onboard starter gas solution and can be converted to kerostart, while others such as the Graupner GBooster
series is delivered as kerostart only.

Tor