Do you know what happened if there sudden change of cabin air pressure or ambient air pressure throughout each B777 phase of flight?? As a passenger, we will definitely feel discomfort such as eardrums pain, headache and nausea if the event of decompression or overpressure in cabin.
So today I am going to share some beside outflow Valve of an 777 aircraft, there is two key components that help in maintain cabin pressure within safe limits. Which is
- Positive Pressure Relief Valves
- Negative Pressure Relief Vent
Positive Pressure Relief Valves
It is a spring loaded door that contain an air filter with pressure sensing line. Whenever there is more pressure inside the airplane than the atmosphere, the valve will open to release the air pressure. It’s flapper door have a plastic tab together with an orange painted edge for easy identification.
The moment you saw the orange outline on the aircraft during your walk around. It means the aircraft experience a positive pressure relief event. And this does not trigger any indication in flight deck but only be verified by walk around inspection and to be reset by the ground engineer simply move the plastic black tab out of the way and push the flapper door back in position.
The sensing port have two one is integrated while other called as remote. it just simply serve as a backup sensing in case the other port line is clogged or failed in providing the ambient pressure.
Negative Pressure Relief Vent
It’s operation are simple. If there is more ambient pressure than in cabin pressure, the outside pressure will pushes on the vents and let’s air go into the airplane. It is also a spring loaded door that only open or closed. The main reason for the negative pressure vent is to prevent negative cabin pressure and also protection of the airplane structure from being crushed by the ambient pressure.
Author- Lim Weeping ( Licensed Aircraft Mechanic)
