Absolutely agree! It’s just nice to know how much is left there in the straight and level, static configuration. Ram air pressure into the fuel caps may play a roll also. Certainly I would never rely on that myself or recommend anyone else do either.

It’s also nice to know how much fuel the tanks really hold in the 3 point config.

Thanks for the additional info.

Quote Originally Posted by Brad Damm View Post
Dave - Great video and very informative as always! The purpose of building an EAB aircraft is education and recreation, and that is a very educational video on how much fuel can still remain in the system even after the placarded amount of useable fuel has been consumed.

Our designers (and FAA regulations) are conservative, and CubCrafters designs, tests, and placards the aircraft to always ensure that enough fuel remains in the system for the engine to continue making power throughout all phases of flight, including various pitch and roll attitudes other than straight and level.

The FAA’s guidance for amateur builders to determine the amount of unusable fuel on their EAB aircraft is on Page 33 of AC 90-89B, which I have linked below. In part, the guidance is to determine unusable fuel at a pitch attitude 5 degrees above the highest anticipated climb angle that the aircraft can achieve. That same Advisory Circular also offers guidance to amateur builders (on Page 17) as how to calibrate their fuel tank indicators. We recommend that amateur builders follow that guidance when building or testing any CubCrafters kit aircraft.

https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_90-89B.pdf

I know you said it in the video, but to emphasize in case anyone out there missed it; it is not safe to run any CubCrafters aircraft down to 1.4 gallons of fuel remaining in the system. At any fuel amount that is less than what is placarded as useable, the aircraft operator is at risk of a loss of power due to fuel starvation.