Hi, I have a problem with the fuel pumps. When i turn off Center Tank Fuel Pumps, the left engine keeps using the fuel from the center tank, but the right engine is using the fuel in the right main tank. My other question is,the Center Tank Fuel Pump Low Pressure lights do not illuminate, even the fuel quantity is less than 500 lbs. They illuminate only, if no fuel remains in the center tank. Am i doing something wrong ? CheersKaan

The manual says turn them off but there is a procedure for when the fuel in them starts to get low. What I am wondering about is why, during setup, the fuel tank switches are flipping themselves on. I can't figure this one out.

The manual says turn them off but there is a procedure for when the fuel in them starts to get low. What I am wondering about is why, during setup, the fuel tank switches are flipping themselves on. I can't figure this one out.

They change automatically when you load fuel using the CDU. Fred.

My other question is,the Center Tank Fuel Pump Low Pressure lights do not illuminate, even the fuel quantity is less than 500 lbs. They illuminate only, if no fuel remains in the center tank. Am i doing something wrong ? CheersKaan

The low pressure lights won't illuminate in the real plane until the tank is almost empty. Since the left pump is forward and the right is aft in the tank sometimes you will see the forward low pressure light come on with around 100 pounds left. The fuel pump AD for the 737 requires us to open the crossfeed and turn one pump off when the center tank reaches 2000 pounds. Doing it this way means the master caution light will come on as soon as the remaining pump has low pressure. Since the plane flies with a nose up attitude we usually leave the right pump on because it is aft in the tank and has access to the most fuel.

The low pressure lights won't illuminate in the real plane until the tank is almost empty. Since the left pump is forward and the right is aft in the tank sometimes you will see the forward low pressure light come on with around 100 pounds left. The fuel pump AD for the 737 requires us to open the crossfeed and turn one pump off when the center tank reaches 2000 pounds. Doing it this way means the master caution light will come on as soon as the remaining pump has low pressure. Since the plane flies with a nose up attitude we usually leave the right pump on because it is aft in the tank and has access to the most fuel.

How do a real 737 react for the below case ? When 100 pounds left in the center tank and both central tank fuel pumps are turned off.In my case, 737 ngx keeps using the fuel in the center tank, no fuel consumption in the left main tank, but the quantity of the fuel in the right main tank is going down.

They change automatically when you load fuel using the CDU. Fred.

Indeed, that's when it happens, so this is a, uh... known bug?

As soon as you turn the center tank pumps off fuel will start feeding from the wing tanks. When main tank number 1 reaches approximately half full and the forward pump is on there is a scavenge pump that will activate and transfer any remaining center tank fuel to main tank number 1. Are you turning the center tank pumps off before the tank is empty?

Indeed, that's when it happens, so this is a, uh... known bug?

No it's not a bug ! See page 13 of the Tutorial-1 PDF. Fred.

No it's not a bug ! See page 13 of the Tutorial-1 PDF. Fred.

Yes, I do remember reading that. The problem, and it is totally my fault for not being clear, is that I have them set to off before loading the fuel. Now, on that page it says they will be set to off if the center tank is empty; however, it does not say they will be turned on if fuel is placed in them. So, doesn't this seem like a bug? I don't see how the FMC loading fuel, with the switches off, would flip the switches in the cockpit on. Doesn't the FCOM vol.1 say to keep the tanks off till passing 10,000? I will try and look that up but I'm pretty sure I read it in there.

As soon as you turn the center tank pumps off fuel will start feeding from the wing tanks. When main tank number 1 reaches approximately half full and the forward pump is on there is a scavenge pump that will activate and transfer any remaining center tank fuel to main tank number 1. Are you turning the center tank pumps off before the tank is empty?

Thanks for the reply. I got my answer. I am turning the center tank pumps off before it is empty.