Positive Pressure and Negative Pressure relief valves MEL B777
Hi there,
I'm looking at the MEL item for Positive and Negative Pressure relief valves.
Positive Pressure Relief Valve: No. installed: 2, No. required: 1
Negative Pressure Relief Valve: No. installed: 4, No. required: 0 but flight has to be conducted unpressurized.
Seems like Negative Pressure Relief Valve is more important than Positive Pressure Relief Valve, why is that so?
Any examples will be good. Thanks for your time