Cowl Flaps?

[Toobuilder]

...While some of the exact failure modes are not known there have been a number of fatal accidents due to fuel plumbing...

Not going to rehash the debate concerning what's better, But I will say that if you are not comfortable with a particular method, then dont use it. Personally, I replace every hose I can with hard line. Hose is only used on my airplanes where there is relative movement. I have many years and hours across several airplanes doing it with no failures.

Use the method that meets requirements, fabricate and install the components correctly, and inspect regularly. That's aircraft design 101.

 

[MacCool]

Just as a brief followup, these are the undercowl temps I recorded yesterday using Pete Howell's datalogger. It uses LM34's, so multiply Y-axis temps by 100. They were secured to the fuel pump, red cube, and gascolator. About 55 minutes from startup to shutdown, and after shutdown until it was clear that temps were all decreasing.

 

[NTex]

Mac, before I spent time and money on cowl flaps, I'd revise the fuel system.

The boost pump should be behind the firewall, where it is cool. Elbows should be minimized in the plumbing between the tank selector and the boost pump. Bring the fuel through the firewall with a SS bulkhead fitting, then run a short, insulated teflon hose directly to the engine driven pump. The red cube should be downstream of the engine driven pump. It's a moderate flow restriction. And do you see a fuel flow change when you switch the boost pump to ON?

Dan curious why you recommend a stainless steel bulkhead fitting vs a carbon steel. Just to match the firewall material or something else?

 

[DanH]

Dan curious why you recommend a stainless steel bulkhead fitting vs a carbon steel. Just to match the firewall material or something else?

Water and/or alcohol content in fuel can cause corrosion with a carbon steel fitting, which sheds rust flakes into the system. I once removed one with what looked like steel wool inside, after finding some in the Bendix inlet screen.