Slow Day, education, and more Fluid

Today started out very slow. I spent time learning about timing the ignition to the engine. The Lycoming manuals are not very descriptive because they are intended to cover a lot of different engines and accessories. To add to that, my combination of engine, ignition, injection, propeller, starter, etc, etc, etc is not something for which Lycoming writes a manual.

My biggest problem was I couldn’t quite figure out why Lycoming had two different timing methodologies. I didn’t know whether you could pick which one you wanted to use, or if the engine required a certain one. The difference is one method uses the case split to align the timing mark, and the other uses a drilled hole in the starter. Well, I have changed my starter and it doesn’t have a timing hole, so I was hoping that I could use the case split method. But I knew that being able to choose which one didn’t sound right, and it wasn’t. So I needed to figure out which method my engine requires.

My buddy Jeff Lange said, “Well, why not pull plugs and see if the cylinders reach top dead center with the timing mark near the starter or near the case split.” DUH. Seems simple. So I did, and I certainly need to time based on the missing hole on the starter. Turns out there is a way to do that with a piston stop and a angle wheel. It is actually pretty simple, and seems to me that it would be more accurate. I was able to borrow that tool set up, so maybe I will get to that tomorrow. (Hopefully I will remember to take some photos of it.)

By the time I learned about this most of the morning was gone. I did manage to make up a line for the mechanical fuel pump pressure relief and find an exit for it out the bottom of the cowl flange. I think I will flox the tube into the flange eventually to keep it vertical, but it is functional the way it is.

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Then Greg arrived and we spent pretty much the whole afternoon securing plumbing and wiring. We put a wrench on every end of every hose as well as every fitting in the oil and fuel systems to be sure they were torqued down. We also made sure that hoses and wires were clamped to prevent unwanted vibrations, chafing, rubbing, etc while still allowing the relative motion between the vibrating engine and “fixed” points on the fuselage and engine mount structure. Part of this was using adel clamps, which can be a pain in the butt. We also made quite a few stand offs with zip ties and short pieces of hose. We still have a few more things to verify routing on and secure, but we are probably about 75% there when it comes to securing things in the engine compartment.

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Note that in the above picture, we do need to add firesleeve over the Red Cube fuel flow meter, but it is not installed yet so that we can verify that the hoses and fittings are not leaking before we cover it up.

Lastly, Kevin and I spent a few hours putting fuel in the strakes for the first time. We started by putting 5 gallons in each tank, sloshing it around and draining it via the quick drain openings. This was intended to wash out the tank and bring any debris that may be in there out through the drain. We were pretty careful when we closed the tanks, and they have been closed ever since. I was pretty certain we wouldn’t get much of anything out of them, and we didn’t. In fact the only thing that ended up in our funnel filters were a few specks that appeared to be bugs that likely made the fatal mistake of landing in the funnel. Once it was drained, we installed the fuel quick drains in place of the plugs that used to be there.

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After that, we put the fuel back in the tanks (again through a filter) and turned the fuel selector on. This brought fuel through the valve, filter, and electronic pump, through the fuselage plumbing all the way back to the firewall. We checked for leaks at any of the fittings in the system. We didn’t find any. 🙂

One of the leading causes of accidents on new homebuilts is a fuel delivery problem. As such, the FAA is getting pretty serous about having new homebuilders do a fuel flow test prior to first flight. So we did one. Basically the test has you put near minimum fuel in the tanks (we used 5 Gallons), put the airplane in a 5 degree nose up attitude, and check what the fuel flow rate is through the fuel system. The requirement for a successful fuel flow test for fuel injected engines is 125% of the maximum fuel flow the engine could require.

There is a formula and charts to figure out what this number is. But for my engine it was 2.08 lbs of fuel per minute. So we got the scale out and timed a minutes worth of fuel flow in the 5 degree nose up attitude with the fuel boost pump on. For the left tank we got 3 lbs 9 oz of fuel in one minute, and for the right tank we got 3 lbs 10 oz of fuel in one minute. That means my fuel system is capable of delivering 219% and 223% of the required fuel flow respectively. I would say that is passing the test with flying colors.

We put the fuel back in the tank. Tomorrow, I will check the inline filter to see if we got any debris that flowed through the system. If there is any signs of debris, we will flow some more fuel until the filter checks clean.

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2 thoughts on “Slow Day, education, and more Fluid”

  1. Timing is not that complicated to establish. On a pusher, it’s easiest to use the marks on the engine side of the flywheel and align them with the top case split line or make a pointer. You just have to make sure when you install the flywheel that the “O” on the flywheel and crank power lug line up. If you have no marks, simply put your finger over the upper spark plug hole and rotate the engine (without spark plugs installed) through and find the TDC compression stroke, install the flywheel with the #1 TDC mark at the 12-o clock position as viewed from the engine side. No piston pinning is required as the mark will be an accurate indicator of rotation position – it can only be installed in increments of the lug pattern.

    From there…use that TDC and advance marks to determine your ignition timing. Follow the instructions on your ignition set for that.

    -James

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