Author Archives: Michael

Fuel Flow Testing

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Time: 4 Hours

An item that needs to be tested and verified is the electric fuel boost pump had enough power or flow to supply the engine with enough fuel in the case the engine driven mechanical pump were to fail. There is a lot of guidance from the EAA and FAA on how to determine this through a process of steps. In the steps you use a formula to determine how much pounds per hour fuel you would need for your specific engines maximum horsepower. You then can convert this to various numbers such as gallons per hour and gallons per minute.

When I built my IO-375-M1S engine at Aerosport power they were re-building their Dino machine so we didn’t get to determine the exact horsepower of my engine, however we think it’s somewhere between 195 and 200 hp. show for my calculations I went with worst case scenario of 200 hp. BSFC(Brake Specific Fuel Consumption) is a factor that some engine manufacturers and it’s a factor that is used to multiply horse power to enter into the formula. If your Engine manufacturer doesn’t provide one you can use .55 as a conservative number.

So my math is 200HP x .55 = 110lbs/hour. That’s how many pounds of fuel my engine needs at its maximum horse power. The FAA says you need to factor in a margin of error, in my case with a fuel injected engine it’s 25%. So I take the 110 lbs/hour x 1.25 = 137.5 lbs/hour. Now 100LL fuel that my engine burns weighs 6 lbs per gal. I can divid the 137.5lbs/hour by 6 to get gals/hour. 137.5 lbs/hr / 6 lbs per gal = 22.92 or round up to 23 gal/hour. We can convert that number to gal/minute by dividing by 60 minutes. 23 gal/hour / 60 minutes = .383 gal/min. So my plan was to use 4 gal of fuel pumped to determine my fuel flows. That way I have a gallon of space in my 5 gallon gas can for spillage and such. So I needed to know how long I have to fill 4 gallons of fuel into the gas can using my boost pump. So I need to pump .383 gal/min, so I took 4 gal / .383 gal/min = 10.44 min. Therefore that’s the bingo number I need, if my pump transfers 4 gal in 10.44 min it is providing just enough fuel, with the 25% factor, to supply my engine at its maximum horse power.

Now that I know what minimum time I have to fill 4 gallons in the fuel can I can test my boost pump to see if it’s up to the challenge. The RV-8 draws fuel from either the right fuel tank or the left fuel tank based on the fuel selection valves position. So I will need to test each tank separately for flow rates. I also need to test the flow in three different aircraft positions, level, 25° pitch up and 10° pitch down. The process is pretty simple, I disconnected the fuel supply line that connects to the engines fuel servo. I added a AN fitting to the end of the line. Attached to the other end was a short piece of aluminum tube that I could slip a clear plastic hose to. This will allow the fuel to flow into a gas can on the ground. So I just needed to put more than four gallons of fuel in a tank, turn the boost pump on and time the fuel as it fills to four gallons. I would repeat this step for the left and right wing in the three different flight positions.

One cool thing about the Vertical Power system I use for virtual circuit breakers is that you can test and control everything on a laptop via an ethernet cable. So I could turn the boost pump on and off at the laptop while standing next to the gas can rather than running around the wing to flip the pump switch in and off.

One other test I did during all of this was to determine my unusable fuel in each tank. The fuel line in the tanks can only pick up so much fuel based on their positions. So the fuel that it can’t pick for the engine is called the unusable fuel. To know this helps in flight planning so that if you put in ten gallons you know that a certain amount of the can’t be used and not figured into the fuel you want to use. To do this test I emptied the tank completely using the fuel drain on the bottom of the wing. Then I added exactly two gallons of fuel to empty wing followed by turning the boost pump on. When the boost pump stopped or almost stopped pumping I turned it off and documented how much came out which told me how much stayed in.

The pump put out double what I needed in all three positions. The results are listed here along with the unusable fuel data. The results are below:

  • Pitch down = Left wing 47gal/hr
  • Pitch down = Right wing 37 gal/hr
  • Level = Left wing 51 gal/hr
  • Level = Right wing 50 gal/hr
  • Pitch up = Left wing 50 gal/hr
  • Pitch up = Right wing 51 gal/hr

Unusable fuel was a little over .25 gal in both tanks. I think I will use 1 gallon as a conservative number for flight planning.

Aircraft Certification

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Time: 0 Hours

With the ball rolling now to finish the airplane sometime this summer I needed to get the process started for getting the plane certified/registered, as N800MF that I already reserved,m. The EAA has a package that includes a handbook to walk you through the process step by step. I also got Vans to start the process of getting me a final “bill of sale” which is required by the FAA to register the RV. each of these process is not quick, Vans takes around 3 weeks and the FAA takes between 90 to 120 days from the time they receive all the required forms, which all are included in the EAA package or you can download them from the FAA.gov website. Once I get the RV officially registered as N800MF I will then comply with a list of requirements needed for an official inspection. I can either use a DAR(Designated Airworthy Representative) or an FAA inspector(which is free) to come and inspect the airplane and all the documentation that’s required for an amateur built aircraft. Lots of moving parts coming together over the next few months.

Since I was ordering this book I also had them ship the new EAA flight test manual and flight test cards. This is a step by step process for the initial flight and subsequent test flights that need to total 40 hours that is called phase 1.

Transponder & ADS-B

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Time: 4 Hours

I installed the transponder and ADS-B units today that arrived from Aircraft Spruce. I had done most of the legwork for this install several years ago by installing the Dynon cables as well as the antennas. I had also created a shelf that I installed both COM radios that would also hold the transponder and the ADS-B units. For those of you that are reading this and unfamiliar, the transponder is the unit that sends a discreet signal to air traffic control for their radar identification. The ADS-B Is a fairly new required system that provides much more detail to air traffic control about where your aircraft is, its movement and information. It also has the ability to receive more information, such as weather radar and airport weather reports.

To start this project I need to remove the shelf which sits just behind the aft baggage compartment.Before I did that I crawled back and laid out where the transponder and ADS-B would go so that the wires and antenna cable’s would not interfere with items like the rudder cables or elevator push/pull tube.

With those spots marked I could remove the shelf and take it to the workbench to install nutplates to hold both units down.I decided long ago to use net plates for all of these so that would make it easy to remove with just a screwdriver for future repairs and maintenance.

A test fit looks great!

I then returned the shelf back to its position and bolted it down with the 4 AN-3 bolts. I connected the Dynon working harnesses to each of the four units. I connected the COM antennae cables to the units. Now that the shop was in place and all the units were secured I could measure for the antenna cables for the transponder and ADS-B units. These require RG-400 coax cable like the COM radios. SteinAir.com has helpful videos online including how to crimp BNC & TNC type connectors you RG-400 coax cable. I did a review since it’s been some time since I did the COM cables. It’s not hard especially if you have the correct crimper. I made the transponder cable the correct length and only had to add a TNC end on the transponder side as I had the antennae side done when I installed the antennae.

I planned on doing the ADS-B cable from the remaining length cut from the transponder cable which means I would need two BNC connectors. One for each end…I only had one remaining in my stock. So I could finish that cable and will get to it next week when it arrives from Aircraft Spruce. Here is what the shelf with the units in place looks like in the tail. I just need to add the antennae cable next week.

I could still finish up the computer side of the install without that cable installed. Dynon makes it pretty simple with step by step instructions. I did have to go back into my notes to remember which serial pins I used for each of the units as you need to tell the SkyView system what’s connected to what. Once that’s done there are just a few settings you need to add like your tail number, aircraft dimensions etc. Once that’s done it was time to test everything and see how it looked on screen. I won’t be able to check the ADS-B until I get the cable installed and I may not get a signal on the ground even with that. So inflight testing will be required then. Here are a few screen grabs of the Dynon. You can see several cool things like the pink “cross hairs” that’s my flight director that having two autopilot Serbia allows for. You can also see the green transponder code of 1200 at the very top of the screen in the first screen grab. The second screen grab the transponder is in the standby mode and the autopilot is engaged, the flight director bars get balls added to the end of the flight director bars to indicate that the autopilot is engaged.

I love build days like this and you get to see some cool stuff come to life. I can’t wait to use all this cool tech in the air!

Autopilot Roll Servo

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Time: 2 Hours

One of the items delivered today was the second autopilot servo that will function as the role component of the autopilot. To install this is exactly the same as the servo I put in for the pitch. One thing I found was that I made an error in the D sub pin layout way back when I installed the servo wiring harness when I was wiring the fuselage. It was not the same layout as what Dynon called in their installation manual, so I needed to correct this. It was the same in the pitch servo harness and I will correct that one as well shortly. So I needed to remove all the pins from the housing and reinstall them in the correct holes.

After inserting the pins correctly i laced the wires and reinstalled the housing.

I had to add pin and housing to the servo wires as well. The process was the same and ended with lacing and the install of the housing.

The install of the servo into the right wing is pretty easy, just three bolts hold it in place followed by two bolts holding the servo arm connected to the aileron bell crank. After torquing all the bolts and applying torque seal I powered up the Dynon Skyview to configure the network for this new servo. The system worked perfect and now I have expert autopilot controls including a flight director.

Aircraft Spruce Delivery

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Today was the first of several deliveries that I will be expecting over the next several weeks. Tricia and I decided that with all the uncertainty of the airline industry and where I will end up in six months that it would be better to have the RV finished so we could fly it away if we need to otherwise we want to enjoy it with all that it can do. So with that said I ordered the Dynon 7” screen, Dynon transponder, Dynon autopilot servo, Dynon ADS-B, Garmin GTN 625xi GPS and most importantly the Hartzell 74” composite 2 blade propellor. The propellor will take somewhere around 8 weeks to finish and we will drive to Piqua Ohio to pick it for fun. I’m not sure how long it will take the Garmin GPS to arrive as it was a special order. The 625xi is the same as the 650xi minus the NAV/COM functions that I don’t need.

So now begins the mad scramble to finish up all the small loose ends that need accomplished.