Purge Return Line HOBBS 195.0 hrs

I had requested information from the guys on VAF about extra stuff to order with my wing kit. I received several responses that were interesting and useful. One of which was the fact that with a FI (fuel injection) system, most guys install a purge return line back to at least one of the fuel tanks. So, of course I had no idea about this so I had to do some research. I'm still learning about this, but I at least got my feet wet on the topic.

This is my take, although its certainly not needed, it is regarded by guys who have done it as a nice option to have. When a fuel injected A/C engine is shut down, the fuel can/will vapor lock because of the hot engine. It usually isnt a problem unless you try a restart before the fuel has had a chance to cool. The added purge line provides a way to pump the 'hot' fuel back into the tank (or tank intake line), then select the other tank and replenish with 'cool' fuel and voila. Guys that dont have this option state that you can put the mixture to idle cut-off, turn on the fuel pump for a few seconds and accomplish the same thing.

Here is an example of a fuel system taken from VAF (Author: Rick Mellor) to give you an idea of what's going on for a typical fuel system in an RV7. As you can see Rick has plumbed in two seperate purge return lines, one to each tank. Although I think that is overkill and will add one more point of failure to the system, I do plan to add one for convenience. Probably will route to the supply line so I dont have to cut another hole in the tank. Bottom line, I shouldnt have to worry about this option until starting on the fuselage and FWF stuff. It was interesting to read about though, always learning when you build one of these suckers...the knowledge base keeps growing!

On a different note, this turned out to be my final shopping list added to my wing kit. Most of it was low dollar stuff except for the deluxe fuel caps, those ran $200! They're proud of those suckers. All told, I spent about an extra $350 on all of this. Always something...

Longeron Angle 7/8/9 AA6-125x3/4x3/4x15'2"
AA6-063x3/4x3/4x6' (extra angle for misc brackets)
Misc grommets of several sizes
50' roll of 3/4" conduit (for wiring)
Flop tube (1)
Deluxe fuel caps (note: $52 total credit for standard version)
Pro-seal (1 qt) ...I realize I may need more later
Fuel tank test kit
AN833-6D (extra for fuel line)
AN833-4D (extra for vent line)
AT0-032X1/4X8' (Soft Al tubing)
AT0-035X3/8X6' (Soft Al tubing)

At OSH, I will be looking at lighting and heated pitot options as I am still undecided on these.

So, the wings are being crated this week, wing stand is built, plans previewed...I am beyond excited to get started on them!