Hi Gordon,
The system utilizes two 3-way solenoid valves to orchestrate the fuel bypass, injector feed and vaporizer flow control. When both valves are de-energized the fuel simply flows into the feed and out the return. This means there is also no possibility of flooding the engine. All of this is under software control so when the startup sequence innitiates the pump runs at a 1/2 power to circulate fuel through the system. At the appropriate time the injector is energised to preheat the combustor. Once combustion temps are steady the vaporiser system valve meters a regulated amount of fuel to spool the engine to idle.
Should a flameout occur the valves are closed to prevent further fuel from entering the injector/vaporisers. The pump is also turned off. Should a pump malfunction occur the fuel will harmlessly flow back to the tanks.
All the hardware is under the front cowl and so is pretty simple to install from the users point of view.
Should the RPM sensor fail for any reason and the failure persists beyond what is considered safe, the engine is shut down/valves closed. This is unlikely as the magnetoresistive RPM sensor is extremely reliable and not subject to blockout like optical systems. This very system was pioneered by NASA for use on the Shuttle main engine turbopumps many years ago. If you look at the startup graph in Garrett's post above you will see just how smooth and quick this process is. The BMT logdata graph viewer software is almost out of Beta testing and should be available soon.
Another pic. This time of the almost "wireless" Turbine control unit. I really hate thick wires on PCB's so all the connectors are on the PCB, including that for the smoke pump. For those who may wonder, the code is just short of 64K of "C" and "ASM", can be loaded by the user from any PC. The TCU decrypts the file using a 1Kbit key when installing the new application.
Cheers
Andre