Forum: F-16 Procedures

This is a fuels question. When the auto drain valve is bad, why does the vent port at the left wing vent air continuously? The book tells you to check the vent, why not the drain itself?

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I just ran accross this post as I have just joined the forum and saw this was un-answered. It tells you to check the vent because if the auto drain is open, supply air from the ECS is being bled off into the atmosphere, thus lowering your input pressure into the internal and external P&V. I'm not sure where you are referring to in the book where it tells you to check the vent port, as opposed to the drain port itself, but the auto drain port wont leak unless the engine is running, or you are using ECS air via the -60. If you are manually pressurizing, the port will not leak because of the check valve downstream of it, unless this is stuck open as well.

So you are saying that if the V&P's don't get enough pressure from the ECS (due to the leaking auto drain valve), the V&P's with vent the air? That would make sense if i'm hearing you straight. That leads to another question, if you hooked up a low pack, and only applied like 10 psi give or take, would it vent air continuously?

If the Internal V&P is working right, and the air ejectors are closing, then 10 psi will work. I believe the external v&p doesnt not pressurize the external tanks until the inlet pressure going to it is 7 psi. What happens is the internal v&p essentially robs all the inlet air coming from the ECS/low-pack. As soon as it pressurizes, it shuts off airflow, which allows the external v&p to open up after 7 psi head pressure. (It may be 8psi). This is why you have to ops check the internal v&p and the air ejectors for proper operation when you have an external tank pressurization issue.

Forum: F-16 Procedures

Automatic drain valve