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A_Pilot

Boost Pump Operation and control

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Heyoo
 

First off, niiiice plane. Love this bird. Love flying it IRL, love teaching guys to fly it in the sims at CAE. Love flying it in P3D. I Noticed this on a different thread, thought I'd toss a chart at the issue. Below is the fuel Boost Pump Logic for the RJ 900.  It's not the most intuitive, so I'll do my best to explain how to interpret it. 

 

First 2 columns are the physical switch position (in or out).

 

Next are the two Main Ejector statuses (which is essentially an indication of whether that engine is running normally ie: main ejector runs if its engine is on, and there's no flow issues)

 

Last is a funky chart form of the lights on the switch. Top is the white ON light, bottom is the amber INOP light. The asterisk denotes which light is on, and pump operation can be determined from the lights: 

 

- The boost pump Dead/off/kaput whenever the amber INOP light is illuminated. 

 

- A White ON indicates the pump is running, typically in abnormal configurations 

 

- A dark switch also indicates a running pump (Typically in normal configurations)

 

Don't know how easy this is to model, but thought I'd give the reference anyways. 
 

 

 

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Yes, The essential thing about starting to understand the fuel boost pumps is that  pressed in “on” is not really/necessarily “on” but instead “armed”.  Once armed  it can turn on or remain off depending on the engines running, proper operations of the main ejector that feeds the engines normally and condition of the other fuel boost pump.       The systems detects the fuel feed pressure and depending on some other factors will be on or remain off.  

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Thanks for that. 

 

In the second table (first case) it is exactly the particularity when testing fuel valve for the first start of the day. And this is not simulate in CRJ pro.

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10 minutes ago, Alex Nicolle said:

Thanks for that. 

 

In the second table (first case) it is exactly the particularity when testing fuel valve for the first start of the day. And this is not simulate in CRJ pro.


I agree that is one wish I have on a crj pro future version as the fuel pump check is done once a day.    I would give priority to simulating these compared to more obscure failures.     Note it is the fuel check valve which makes sure the boost  pump from the opposite side fuel system is not feeding a fire on a failed engine side.    

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1 hour ago, wwittkoff said:

Yes, The essential thing about starting to understand the fuel boost pumps is that  pressed in “on” is not really/necessarily “on” but instead “armed”.  Once armed  it can turn on or remain off depending on the engines running, proper operations of the main ejector that feeds the engines normally and condition of the other fuel boost pump.       The systems detects the fuel feed pressure and depending on some other factors will be on or remain off.  

 

Actually, the way it works is that anytime the switch is IN, that pump will be ON (but the "on" light might not be!). A careful read of the charts shows that if one engine is running, and the wrong pump is selected, both are fired up. 

 

What's funky is the pump that's switched OUT can be forced ON by the other switch, based on that chart (in which case you'll be given the *ON* light to show the override).

 

To say that the pump is "armed" based on the switch isn't quite accurate. The pump can be ON, without the ON light, and this would be evidenced on the FUEL system page by the green color on the pump itself. (which is different from the lights in the switch). 

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Yes Thanks,  I stand corrected. : ).     Perhaps the better way to say it would be that pressing in either fuel boost pump will arm the boost system in which case more complex pressure control logic on each engine feed takes over as evidence of the table above.   

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2 hours ago, wwittkoff said:

Yes Thanks,  I stand corrected. : ).     Perhaps the better way to say it would be that pressing in either fuel boost pump will arm the boost system in which case more complex pressure control logic on each engine feed takes over as evidence of the table above.   

 

bingo

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I changed the fuel boost pump logic a while ago. It will be available for testing (as part of SP1 and the P3Dv5 version) by the end of this week. If any of you is interested in participating in the test, please send me a PM (A_Pilot is already on the list ;) )

 

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I love a fun and silly analogy. My systems instructor used “the Batman and Robin” analogy. The left pump is Batman and the right pump is Robin. Their enemy is low fuel pressure at the main ejector.

When the left pump switch is in, Batman is only watching the left main ejector pressure. When the right pump switch is in, Robin is only watching the right main ejector pressure.

For example, when the left engine is shut down on the ground during taxi, Batman sees low pressure on the left main ejector, he sounds the call to go to battle. Both Batman and Robin will go to fight the enemy by turning both the left and right boost pumps. If the left switch is then selected out, Batman goes back to his layer. Robin remains on watch but only sees the right main ejector. Because the right side is still normal in the scenario, Robin sees no danger and will turn off both boost pumps.

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7 hours ago, andy51edge said:

I love a fun and silly analogy. My systems instructor used “the Batman and Robin” analogy. The left pump is Batman and the right pump is Robin. Their enemy is low fuel pressure at the main ejector.

When the left pump switch is in, Batman is only watching the left main ejector pressure. When the right pump switch is in, Robin is only watching the right main ejector pressure.

For example, when the left engine is shut down on the ground during taxi, Batman sees low pressure on the left main ejector, he sounds the call to go to battle. Both Batman and Robin will go to fight the enemy by turning both the left and right boost pumps. If the left switch is then selected out, Batman goes back to his layer. Robin remains on watch but only sees the right main ejector. Because the right side is still normal in the scenario, Robin sees no danger and will turn off both boost pumps.

 

Clooooose, this analogy works to explain the lights on the switches. Left eng off, left switch out, the right pump will still run if the switch is in, which by your Robin example, I think you said the right switch is still in, yes?

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