B204 Fuel Start Switch

[Guest jacdor]

It has been a little while since I have flown a regular 204 (-11) and I can't remember why you have to put the "start fuel switch" back on once the engine is running and you are ready to go.

 

Any mechanical/engine reasons for that? http://www.verticalmag.com/forums/style_em...fault/wacko.gif

[arctic_front]

I think the start-fuel only works when the starter is engaged. Therefore, by putting it back into the 'on' positions, you have it ready in case of a flame-out and a in-flight restart attempt. I may not be correct on that, but I think that is why.

[Heliman2]

I think the start-fuel only works when the starter is engaged. Therefore, by putting it back into the 'on' positions, you have it ready in case of a flame-out and a in-flight restart attempt. I may not be correct on that, but I think that is why.

 

Artic Front is correct with what he stated..... During the start cyle it turns off atomatically as well with N1 speed (air pressure in the burner can) and blows air thru the nozzles to prevent them from coking up. Sorry if thats too much info...

[xdm785]

jacdor

 

The reason the fuel start fuel switch of a 204 with a -11 is returned to the on position after a start is to prevent carbon build-up on the start fuel nozzles. Fuel under pressure is feed through them for the duration of the engine run. The -13 however uses P4 air to vent the start fuel nozzles after the start fuel is either turned off or the starter trigger is released.

 

On the 204s and a few of the early 205s the start fuel is controlled only by the start fuel switch however on the later 205s the start fuel switch was never installed and control of the start fuel was with the starter switch. Some opperators have rewired their 205s incorporating a start fuel switch which can provide a little more control of start temperatures.

[xdm785]

jacdor

 

I received your PM (message) ?? but am unsure how to respond directly to you. My appologies for not being more clear in my original description of the start systems on the -11 and on the -13 engines. You've got the right idea, but not exactly. On the 204 with the -11, the start fuel switch is returned to the "ON" position after the start is completed to keep fuel flowing through the start nozzles, therby preventing the build up of carbon on them.

 

With the -13 engine, the start fuel is either turned off at 45%N1 or when the starter trigger is released. After this happens a check valve automaticly reposissions to allow P4 air to flow through the start fuel lines and manifold to the nozzles. This P4 air vents the start fuel nozzles preventing carbon build up.

 

To sum it up briefly, the -11 uses fuel under pressure to keep the start nozzles clean and the -13 uses P4 air pressure to do the same thing. Maybe I should have just said this first. Hope this helps