Engine Start up w/o fuel pumps

[b747]

Hello I have a question to which i can´t find an answer.

The engines will start will all the fuel pumps off, is this behaviour correct?

I know that for the APU this behaviour is correct because it has its fuel pump operated of its own.

Thank you

[richboy2307]

Hi @b747

That is a feature not a bug.

Fuel is gravity fed to the engines even without the pumps being on. The only way to absolutely cut-off fuel feeding is by engaging any of the fuel fire shutoff valves. These valves close when their respective Fire handle is pulled.

The pumps switches on the overhead control the "Electrical Fuel Booster Pumps" (keyword being Booster). These help ensure sufficient continuous pressure for transfer between tanks, which is particularly important for low fuel or extreme pitch attitudes, bank angles etc or high continuous demand which can exceed the gravity fuel feeding rate (e.g Takeoff thrust). 

Thanks!

[b747]

Thank you!