Originally Posted by
Trufactor7
Fuel pump boost questions...after the engines are started on the CRJ does the fuel pump boost light go off or does it stay on ??? I am studying the regional jet course and i am confused on the part on the before start flow where it says to push the L & R fuel boost pumps on and 2 white lights should come on indicating on...but on the after start flow it says verify that the fuel pumps are on but the fuel panel should be dark..can anybody verify this..thanks
Trufactor,
It's been 7+ years but I'll try and answer this for you. The CRJ like most modern cockpits works off the dark cockpit principle. That means when all systems are powered and you are at the end of the runway ready for takeoff, the cockpits dark. Any light on would signify there is a non-normal condition. Not necessarily abnormal, just non-normal.
In the case of the boost pumps, when selected prior to engine start the pumps come on when pressed in and the lights are on to signify they are working. In this case, it is a status message which means that the system is letting you know its not normal for the boost pumps only to be on but they are working. The reason they are status lights is because the boost pumps are only used until there is sufficient fuel pressure from the engine driven pumps and primary ejectors to take over the load. The engine driven pumps boost the fuel pressure to around 800 psi whereas the electric pumps are around 50 psi I think. That's why if you lose an engine driven pump the engine fails no matter how many electric pumps are available.
The electric pumps only exist to provide positive pressure to the engine driven pumps and augment the primary ejector. The primary ejector has no moving parts and is simply a siphon. Once you get suction from it, it stays on until you stop the flow. At some point during engine start, the primary ejector gets enough suction pressure to take over the load from the electric pump. The system senses this and the electric pump which was selected on, goes into a standby mode. If for any reason, the electric pump senses low pressure to the engine driven pump, it turns on to ensure positive pressure to the engine driven pump.
Since the electric pump is in standby, you don't have any lights on. The only reason you would get an electric pump light following engine start is if there is a primary ejector failure, or an engine is shut down.
Its been awhile but hope that helps. I spent a lot of time on the RJ years ago. IMO, it was the most challenging plane from a systems standpoint to learn. Once learned however, its hard to forget and is a very straight forward airplane. Good luck. You will enjoy it.
Let me know if you need any help with AUTOXFER FAIL.