A lot of people/builders opt to not install valves, as it has happened more than once that "service valves" are turned off inadvertently, as you as the pilot don't check as you have not turned them off yourself and walla fuel starvation as you rotate and the expenses start...

That is used by the pilot as a sight gauge - you can see the level of fluid in the tank also appear in the hose.!

@@HomebuiltHELP Thanks for the fast reply. I thought it was that but it didn't look transparent enough to me. Clearly I was wrong ;)

Well... I might ask - how often do you fill one tank while the other one is completely empty? It might vent OK in that situation! You are creating odd scenarios where a header tank might not need a vent. This is an airplane and we want a definite vent to work always. A trapped pocket/bubble in the header tank is deadly for an airplane.

@@HomebuiltHELP It will vent even better if neither tank tank ever gets empty enough to allow air into the header tank as each tank supply line serves as the vent. You can’t lower the pressure in the header tank if either of the wing tank feed lines is unobstructed. The only purpose of a vent line is to prevent a loss of pressure in a tank such that the liquid in the tank can’t drain out. In the case of the header tank, the wing tank supply lines serve that purpose.

No, no, no! Read your last 2 sentences. It is when the 2 wing tank lines become obstructed (at the same time - blockage, crimp, when fuel tank vent goes negative - lots of reasons, etc) that you NEED a header vent to allow fuel to leave header tank. Without its own vent in this scenario, fuel could not leave and then engine will stop. With a vent, you have a calculated time to look for a landing field as you watch the header fuel gauge creep to zero. I see this all the time - builders that dont "see" a reason for that extra vent get into real trouble later. Worse is telling others that you dont need one. You dont often see comments on my channel of dangerous advice because I remove them. These are airplanes - not boats or cars... so engine stopping is serious business.

@@HomebuiltHELP I agree. And how many times are both fuel lines from the wing tanks to the header tank blocked? It is more likely that the fuel line from the header tank to the engine would get blocked than both fuel tank lines would get blocked at the same time. What scenario(s) have you seen where both fuel lines to the header tank from the wing tank were obstructed simultaneously?

@@HomebuiltHELP Also, I never told anyone else what they do or don’t need on their airplane. I asked a question and am exploring a topic. I’ve read lots of claims about a gravity fed header tank needing a separate vent, but I’ve never seen a rationale provided for this. And I have searched the NTSB accident database and have never seen an accident caused by an unvented gravity fed header tank. Obviously, header tanks that are pump fed to transfer fuel from a wing tank that may be lower than the header tank is an entirely different animal with different considerations. I’d love to see a rationale for this that makes sense or an accident report where this was identified as the cause of the accident.

Worst still annoying comments about irrelevant aspects of the video