BEARHAWK ~ Fuel Flow Test (Part 2 Airworthiness Certification and Phase 1 Flight Testing)

[@ludvikblondal9885]

Reminds me..I buildt a kitfox...so much fun ...400 hrs. Of flying in fact ..nothing like experimental aviation

[@TheBaldPilot]

Yes it is really fun!

[@danielbasovitch5087]

Thanks for the explanation and information. I didn't realize that it got so concise and specific. I can only imagine a fully aerobatic aircraft calculation must be a nightmare.

[@TheBaldPilot]

Yeah! And so many openings for interpretation!

[@scratchbuilder5952]

Great content

[@TheBaldPilot]

Thank you!

[@kcpumpguy]

I don't understand something here. I got all the BSHP calculations and they look correct. What I'm missing is the fact that you don't seem to be taking into account the engine-driven fuel pump when you are calculating the required flow. The engine-driven fuel pump is going to lower the pressure in the fuel lines from the tank so it will flow more than it would through gravity alone. For example, my Bonanza has a 300Hp IO-550 and it burns around 28.5 gallons per hour on takeoff. The difference is that it's a low wing so zero fuel will flow to the engine-driven pump when the engine is not running. The pump is drawing a suction lift to get the fuel up out of the tanks and to the engine. The boost pump on a Continental is only used for priming the engine pump to get it started and emergencies. It's off for takeoffs and landings. Your setup passed your test, but I think the target numbers are much much higher than necessary. I know you have a Lycoming, not a Continental. But the logic is the same; if the fuel needed to flow to the pump via gravity, there would be a whole bunch of Pipers and RVs that wouldn't work (low wings).

[@TheBaldPilot]

I think what we are seeing is correct. The ultimate goal of this test was to determine gravity flow to the engine driven fuel pump with low tanks and high deck angle. We want no suction at the engine driven pump.

[@daverobinsonTnT]

Rob, I got to admit I was a bit worried as you elevated the aircraft (in pitch) with only the tail wheel secured by chocks and also there appeared to be no one there with you in the unfortunate event that there was a mishap, god forbid. Great video by the way (two thumbs up). Appreciate you sharing it. Suggestion : ------------------- Anyone working around a prop should place large foam pieces on the tips of the prop, so you don't accidently incur an unwanted head injury by walking into the prop.

[@TheBaldPilot]

Appreciate the concern. There was another guy at the front of the hangar working on his Mooney.

[@danielh4759]

Loving these vids. Just got my plans this week. Hopefully will have the kit this summer. On your gravity test.....wouldn't you get more flow in flight due to pressure in the tanks from the forward facing vents? Does the ground test values already account for the that?

[@TheBaldPilot]

It's a great kit! I would imagine that there would be slightly more pressure on the forward ports in level flight. The ground test assumes the worst case scenario. You have flown until almost fuel exhaustion, lost your boost pump, and are now about to land and have to perform a go-around. You are pitched up and climbing out with no boost. Will there be enough gravity flow fuel to the engine driven pump to keep flying?

[@j.muckafignotti4226]

I’m sure you know what is happening but I don’t like it, no sir, not one bit!

[@TheBaldPilot]

Ok! Thanks for watching!

[@j.muckafignotti4226]

@@TheBaldPilot I really want to be there when you fly that thing. You have done such a wonderful job. I also had some questionable fuel flow issues with the Murphy with the monster 350 hp Lycon I had in it. If you didn’t have the boost pumps on you were going to have a very bad day. When are you looking at having your first flight, any ideas yet?

[@danielbasovitch5087]

Are the specified amounts and percentages for that engine according to FAA? Or is it for the high wing configuration?

[@TheBaldPilot]

No reference whether high wing or low wing. However the FAA doesn't specifically say Brake Specific Horsepower Fuel Consumption (BSFC), it basically spell out the same formula in AC 90.89B for determining the fuel flow rate starting on page 33. "Fuel Flow. A fuel flow and unusable fuel check is a field test to ensure the aircraft engine will get enough fuel to run properly, even if the aircraft is in a steep climb or stall attitude, and is accomplished by: (1) Place the aircraft’s nose at an angle 5 degrees above the highest anticipated climb angle. The easiest and safest way to do this with a conventional gear aircraft is to dig a hole and place the aircraft’s tail in it. For a nose gear aircraft, build a ramp to raise the nose gear to the proper angle. (2) Make sure the aircraft is tied-down and chocked. With minimum fuel in the tanks, disconnect the fuel line to the carburetor. The fuel flow with a gravity flow system should be 150 percent of the fuel consumption of the engine at full throttle. With a fuel system that is pressurized, the fuel flow should be at least 125 percent. When the fuel stops flowing, the remaining fuel is the “unusable fuel” quantity. (3) The formula for fuel flow rate for a gravity-feed fuel system is 0.55 times engine horsepower (HP) times 1.50. This gives a fuel flow rate in pounds of fuel per hour. Divide the pounds-per-hour number by 60 to calculate pounds per minute, and divide again by 6 to calculate gallons per minute. To get gallons per hour for Avgas divide pounds per hour by 6; or multiple gallons per minute by 60. For a pressurized system, substitute 1.25 for 1.50 to calculate the fuel flow rate. (4) The fuel consumption rate of most modern engines is about 0.55 pounds per hour per brake HP."

[@countryflyer4536]

I couldnt make it to the content, the music is horrible!!!!

[@TheBaldPilot]

Thanks for (attempting) to watch!