Gulfstream IV Walkaround Question

[balaton]

Dear, respected G-IV guys,
What are the vent ports (2) on the LH lower fuselage in front of the LH wing, roughly under cabin windows No 1 and 2 marked: "VENT - DO NOT BLOCK" ?
No reference can be found in the AFM "EXTERIOR INSPECTION" section or Training Manuals.
I really appreciate your help.

[themoonsaballoon]

Balaton,
The Oxygen bottles live under the floor in the forward cabin,these ports are the oxygen overpressure relief ports,
TMAB

[g4phil]

Balaton,

The opening you are referring to is the pressure fueling sensing valve:

Quote from training manual.

Pressure-Fueling Sensing Valve
The pressure-fueling sensing valve is located at the structural rib at BL90.0. The valve senses the difference between the outside ambient pressure and the pressure in the tank during the pressure-fueling. The valve functions to stop the pressure-fueling process if the pressure in the tank increases to the maximum differential value of the valve, such as a vent system blockage. Air pressure within the tank is sensed on the diaphragm of the pressure-sensing valve.

If the tank pressure does not balance with the outside ambient pressure, the valve closes. This in turn causes back pressure to build up in the pressure-sensing line to the pressure-fueling SOV, causing it to shut off. The ambient vent for the pressure-fueling sensing valve is a small opening exiting out of the bottom surface of the wing skin, which must remain clear. This opening can easily be overlooked. Regular inspection of this opening will prevent anomalies during pressure refueling.

themoonisabaloon....

The oxygen high pressure relief port is normally located on the lower fuselage, this is normally a green disc, when the disc is blown the interior is red in colour and is easy to pick up on a pre-flight.

Regards,


Phil

[balaton]

You are right TMAB, these are oxy. H.P. relief ports with green discs in them. I have checked it. One for the pax one for crew bottles. It is strange that these are not in the Exterior Inspection items in the AFM.
Best rgds,
balaton

[balaton]

Thank you Phil. These are the Oxy H.P. reliefs. I have just checked the green discs. I was misled a bit since these are not in the Ext. Inspection items.
The Pressure Refueling Ambient Sense Ports are actually under the wings in front of the main gear struts near the leading edge.
But thank you for the excellent explanation I am not sure I was aware of their exact function.
Best rgds,
balaton