Why Positive Pressure Fuel Caps on 180hp Conv

[Pacer42Z]

There was a Jensen STC to install a nylon plug in the fuel selector with a both position and it called out welding a nipple into each filler neck to vent the two tanks together. They are no longer in business.

Thanks Steve, not sure if I want to do welding on my gas tanks anyway.

Juergen
Pacer N3342Z

[Rick-CAS]

The Night and Day seaplane door STC drawings have the Jenson fuel mod in them. They are on the Drawing CD.

[Tp109]

If you cross vent and somehow lose a cap.. I haven't done it but read here in the forum about someone leaving a cap behind after gassing up, if you have a cross vent connecting both tanks and you lose a cap in flight will you lose not only the gas in the tank without the cap but also the gas in the the tank with a cap?

I haven't flown a Cub with tanks connected, I like the way Piper designed the system works well.

I did that flow test yesterday out of my firewall gascolator and it gravity flowed 28 gallons an hour with almost empty tank, had less than 5 gallons in it and still flowed 28 gallons an hour, I wonder how fast a low pressure on the upper surface of a wing can pull the gas out of the tank if you lose a cap?

This brings up another question about the Timmer STC gooseneck gas caps, my test revealed that 28 gph flow with standard vented caps not the ram air gooseneck caps, question I have is how do they know the flow of the gooseneck ram air cap? Do the hook an air compressor to the gooseneck and simulate the ram air of flying speed? We know from the previous posts the ram air gooseneck caps are required with an O-360 in order to meet 150% of Lycomings 22 gallons per hour the O-360 requires, which is 34 gallons per hour. Standard gravity flow for my test with plain non gooseneck caps flowed 28 gph, I want to know how much ram air into the gooseneck is required to meet that 34gph that the O-360 needs?

I wonder how Piper is allowed to decrease the required fuel flow to the flight planning flows which are about half of the 22 gallons per hour that Lycoming says the O-360 requires?

[Steve Pierce]

Piper didn't install an O-360 in the Pacer nor the Super Cub and I have never seen a POH that considered full power for cruise flight. Maybe you should call Eddie and ask him why he used the positive vent gas caps and look up the FAA fuel flow requirements for certification and let us know all the specifics. Sounds like Dakota Cub, Cub Crafters and Eddie Trimmer are changing fuel caps for not.

[Steve Pierce]

An FYI, Dakota Cub had to use 1/2" fuel line on the Super 18 to get the airplane certified to proper fuel flow requirements.

[Tp109]

Life is too short to waste 1 minute on things that aren't important, I won't research it because it will come up empty with the only reason being fuel flow well above what could every possibly happen, if the FAA want's to require an ungodly amount of fuel to flow than so be it. I am going off my own experience of running wide open in a O-360 powered Super Cub for over an hour several times and the engine never quit and it had plain old non ram air gas caps. I carried 54 gallons of gas and the fuel flow couldn't have been anywhere near 22 gph because I didn't run out of gas, I flew 5.5 hour legs. After the first hour I was able to fly without full power, and gradually decreased it but never below 2300 rpm, my watch was my fuel gauge, I always got 4 hours out of the two right tanks so math told me I had 2 hours out of the left tank.

Enough time wasted. On to the things that are important in life, the gym, eating healthy and living doing the things that make you happy.

[Steve Pierce]

Life is too short to waste 1 minute on things that aren't important, I won't research it because it will come up empty with the only reason being fuel flow well above what could every possibly happen, if the FAA want's to require an ungodly amount of fuel to flow than so be it. I am going off my own experience of running wide open in a O-360 powered Super Cub for over an hour several times and the engine never quit and it had plain old non ram air gas caps. I carried 54 gallons of gas and the fuel flow couldn't have been anywhere near 22 gph because I didn't run out of gas, I flew 6 hour legs.

Enough time wasted. On to the things that are important in life, the gym, eating healthy and living doing the things that make you happy.

Funny that you are the one that has hammered this issue even after you were told the reasoning. Way easier to type on a computer keyboard than to actually research and find out. Seems you and Semper Fi have several things in common.

[Clayton Harper]

Life is too short to waste 1 minute on things that aren't important, I won't research it because it will come up empty with the only reason being fuel flow well above what could every possibly happen, if the FAA want's to require an ungodly amount of fuel to flow than so be it. I am going off my own experience of running wide open in a O-360 powered Super Cub for over an hour several times and the engine never quit and it had plain old non ram air gas caps. I carried 54 gallons of gas and the fuel flow couldn't have been anywhere near 22 gph because I didn't run out of gas, I flew 5.5 hour legs. After the first hour I was able to fly without full power, and gradually decreased it but never below 2300 rpm, my watch was my fuel gauge, I always got 4 hours out of the two right tanks so math told me I had 2 hours out of the left tank.

Enough time wasted. On to the things that are important in life, the gym, eating healthy and living doing the things that make you happy.

My son said to me once, and I believe it holds true with this statement. "That's just crazy talk."

[piperrocks2013]

Life is too short to waste 1 minute on things that aren't important, I won't research it because it will come up empty with the only reason being fuel flow well above what could every possibly happen, if the FAA want's to require an ungodly amount of fuel to flow than so be it. I am going off my own experience of running wide open in a O-360 powered Super Cub for over an hour several times and the engine never quit and it had plain old non ram air gas caps. I carried 54 gallons of gas and the fuel flow couldn't have been anywhere near 22 gph because I didn't run out of gas, I flew 5.5 hour legs. After the first hour I was able to fly without full power, and gradually decreased it but never below 2300 rpm, my watch was my fuel gauge, I always got 4 hours out of the two right tanks so math told me I had 2 hours out of the left tank.

Enough time wasted. On to the things that are important in life, the gym, eating healthy and living doing the things that make you happy.

Not Sure about the O360 but I have O320 Straight Pipe Exhaust with EI calibrated Fuel Flow. Full Power at 1600 ASL at around 70 Degrees F My fuel burn is pinned at 17.8 GPH. when I was with the Stock exhaust Full Power was around 14.3 GPH. Keep in mind my straight pipe gives me another 100 rpm min on the top end. Cruise at 2500 22" Manifold is around 9 GPH or slightly less. I know engineer with a Cherokee O360 claimed 20 GPH at Full Power.

Jared

[Gilbert Pierce]

Life is too short to follow this ridiculous thread.
seems to me TP109 should take the issue up with the FAA Certifiction Branch or drop it.