Some designs also silence the fire bell....automatically.
Keep in mind also that many of these electrically operated fire pull handles activate certain functions, powered directly from the (always) hot battery bus.
Many variations, depending on specific aircraft type.
Pilots should know what these functions are, for example...
Type L1011.
The pilot walks onto the flight deck, and finds no ground power connected, APU not operating, and the ships battery switch in the OFF position.
Then, he pulls the number one engine fire pull handle.
This action sends electrical power to close the number one engine tank valve, because the DC power comes from the (always hot) battery bus.
The question then is...can the pilot confirm that the respective tank valve has closed?
The answer is yes, because...the blue valve intransit light will illuminate briefly, as the valve closes.
Further, now that the engine fire handle is pulled, can both engine fire extinguishers be discharged?
The answer is yes, because, DC power is available from the hot battery bus.
Last edited by 411A; 11th Nov 2009 at 04:53.