RAF Techie 101;
Here is a section from the QinetiQ Nimrod Fuel System Zonal Hazard Assessment Report, dated Sept 2007:
"High Risk: Inboard ram-air inlet downstream of water separator (Port and Starboard)
The vent pipes that normally convey ram air from the inboard intake to the vent system run through a particularly cluttered bay (on both sides of the aircraft) inboard of rib 1. Hydraulic pipes, flying control cables, fire detectors, anti-icing and bomb-bay heating ducts, electrical looms and terminal blocks, as well as other fuel system pipework and components are all present. Whilst the pipes would normally convey air, fuel can find its way into the vent lines folowing an overfill or during aircraft manoeuvres and potentially, could leak into this hazardous area"
The report also points out that another High Risk area is in the wing Root vent pipe couplings, and a Very High Risk is associated with the Tank 7 vent pipe connectors.
So, do you think you should be testing vent lines for air leaks, or fuel leaks? I am sure that you are well aware that FRS coupling seals behave differently for air and fuel. In fact the more you expose them to air, the bigger the problem because the dry out
DV