What is the effect on the center tank fuel pumps with the fuel MODE SEL switch in MAN and CTR TK pump switches ON?

When the fuel MODE SEL switch is set to MAN and the center tank (CTR TK) pump switches are turned ON, the center tank fuel pumps will operate continuously. This is because, in MAN (manual) mode, the control is taken away from the automatic system, and the operator directly manages the fuel pump operation. The continuous operation will last until the CTR TK pump switches are turned OFF by the pilot.

In contrast, when the MODE SEL switch is in AUTO, the operation of the center tank fuel pumps would be managed automatically based on fuel requirements and conditions, such as the position of the slats or the amount of fuel in the tank. However, in this scenario with the switch in MAN, the manual control results in uninterrupted function of the pumps as long as they are switched ON, emphasizing the importance of understanding manual versus automatic control modes in aircraft fuel systems.