The tests do seem like overkill and are without a doubt a lot of work. However, fuel system failures are a significant cause of fatal accidents in new experimental amateur-built airplanes,accounting for almost 1/3 of all in-flight engine failuresin experimental amateur-built aircraft.Sticking with a well-proven design for your fuel system is a very good idea. Most creative fuel system designs that I have seen are less safe than the simple, proven designs used by most kit makers.

The Homebuilt Aircraft Council is asking kit manufacturers to do this testing and make it available to builders, so they can eliminate the tilt tests if they stick to the kit manufacturer's fuel system design. However, if you have designed the plane yourself or have designed your own fuel system, all of these tests need to be done to be sure your fuel system will work in all normal flight conditions. And even if the manufacturer has completed the most extensive testing regimen, you still need to do the basic level fuel flow test on your own plane and should verify fuel flow in all attitudes during your Phase I flight testing.