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A cold front went through on Friday, and the wind was really blowing on Saturday - gusts to 35 kt in Ottawa, and it looked similar in Smiths Falls. The winds stayed high all day, so I didn’t even consider going flying. I went out to the airport for the morning, to get the engine data recording hooked up and tested, and to troubleshoot a VHF COM issue.

I had discovered a problem with COM 1 (a GNS 430W) during the previous aborted flight attempt. There was no TX indication on the GNS 430W when I attempted to transmit. I switched to COM 2 (a Microair 760) - it worked fine.

On Saturday I pulled the GNS 430W from its tray, and used a multimeter to see if the Push To Talk (PTT) signal was making it to the radio. I was very happy to discover that no PTT signal was present at the radio, as that meant the problem wasn’t in the GNS 430W. I knew the PTT signal was making it to the PMA–4000 audio panel, as COM 2 worked. So the problem was either in the audio panel, or in the wiring between the audio panel and the GNS 430W. The next logical step was to check the wiring harness between the audio panel and the radio, but I had forgotten to bring the installation manual which would tell me which pin in the connector to check.

This morning I went back to the hangar, armed with the connector pin-out for the audio panel. I had woken up in the middle of the night with the realization that there was a connector in the wiring harness between the audio panel and the GNS–430W, and that this was a logical thing to check. I crawled under the panel this morning, and found that my problem was self-induced. I had pulled the autopilot from the instrument panel in August to send it back for a firmware update. I had disconnected the connector in the harness between the audio panel and the GNS 430W so I could move the harness out of the way to allow me to get the autopilot out, and I had neglected to reconnect it. I hooked it back up, and a radio test showed everything was now working.

Next I did two high speed taxi runs, accelerating up to 80 kt, then rolling to a stop at the end of the runway. The engine pulled strongly the whole time the throttle was forward, with no hint of the drop in power that I had seen the previous weekend. I looked at the recorded data over lunch, and everything was completely normal.

After lunch I went flying. The engine behaved perfectly, with no anomalies at all. I did a 2.5 hour flight, following the instructions in Lycoming Service Instruction 1427C. I ran at 75% power for one hour, followed by an hour with the power alternating between 65% and 75%, followed by 30 minutes at full throttle and max rpm at 2500 ft. The only issue I noted is that the prop governor max rpm stop needs to be tweaked, as the rpm during take-off was about 50 rpm too low during take-off and about 100 rpm too low once everything was up to working temperature.

The next step is to pull the cowlings and do a full inspection, and adjust the prop governor max rpm stop.

I’m still somewhat troubled in that I never found a definitive cause for the engine issues I had last weekend. I found and fixed a few things which might possibly have caused the problem, but there is no way to know if any of them were the cause. The three leading candidate causes are:

  1. Electronic ignition firing at wrong time due interference from spark plug leading touching coax cable between electronic ignition control box and ignition coil.
  2. Fuel valve not fully open. I had changed fuel tanks prior to the runup, and maybe I didn’t turn the fuel valve all the way to the stop, resulting in a flow restriction.
  3. Bad quality fuel - the last fuel I purchased before removing the engine was in Yarmouth, NS in early July. Yarmouth has very little flying activity now, so it is possible this fuel had been in the storage tanks for many months, followed by almost four months in my tanks. I had to wait quite a while for two aircraft to land downwind before my attempted take-off, and perhaps it was warm enough in the engine compartment for bad quality fuel to vapour lock.

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I had booked a half day off this afternoon to do some Christmas shopping. But, the weather was so nice that I decided to go flying instead. This time of year you never know when the next good weather is coming, so you don’t want to miss a chance.

I got a 1.3 hr flight in. The engine is working well. I set up the maximum and minimum airspeed protections on the autopilot, as they had gotten reset during the software upgrade. After resetting them I confirmed both protections were working as expected. I also did an autopilot coupled RNAV approach, including a missed approach to the missed approach holding pattern. I don’t know when Garmin added a missed approach holding pattern to the database, but it’s there now, and the autopilot does a perfect job of flying it.

When I arrived at the airport I noted a rare aircraft on the ramp - a Max Holste MH–1521 Broussard. The MH–1521 is a French design, roughly comparable to the DeHavilland Canada Beaver. I saw several of them when I was in France for a year in the 1980s, but I didn’t realize that there were any in Canada. It turns out that there are two registered in Canada. This one had been sold and was on a ferry flight, being delivered to its new owner when the engine oil pressure started to fall. The pilot wisely diverted to Smiths Falls. He was not looking forward to calling the new owner to inform him of the problem. The poor owner had never even seen the aircraft yet.

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I finally got the engine installation finished, and did the first engine run mid afternoon today. No leaks, as near as I can tell after a three minute run. All engine instruments were working properly. The engine was running a bit ragged though, with occasional pops from after firing in the exhaust. The EGT on #1 cylinder was much higher than the others, no matter which ignition system was selected, so I suspect a partially plugged fuel injection nozzle. I couldn’t troubleshoot that today, as I got an call from home saying that one of our garage doors was stuck partially open.

I hope to get out to the hangar some evening this week to troubleshoot the rough running.

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I’m making depressingly slow progress on the engine reinstallation. I’m not able to get as much time at the hangar as I would like, as I’m very busy at work. When I am at the hangar, I’ve been slowed down by two issues:

  1. When Aero Sport Power inspected the engine, they found the aluminum oil pump housing was impregnated with steel shavings. The oil pump housing is part of the crankcase, so they replaced my crankcase. The new crankcase is a different part number than my original one, and it has additional metal in some areas. This has affected the fit of some of the baffle pieces, which means I spent way too much time doing test fits, then remove a bit more material, then another test fit, etc.
  2. I’m changing the way the exhaust pipes are supported. When I built mine originally, I followed Larry Vetterman’s instructions at the time, which were to hang the exhaust from the engine mount. Now that I am reinstalling the engine, I’m moving to his later guidance to hang the exhaust from the back of the oil sump. But, I’ve spent a huge amount of time trying to find a way to get a straight shot from the left exhaust pipe to one of the oil sump bolts. An engine mount tube is in the way, as is my heat muff on the pipe from cylinder #4. I posted a request on the VAF Forums, looking for pictures of other builder’s installations. I got several useful responses, some on the web, and some via email. I studied things a bit more today, and I think I have it figured out. I hope to finish this off the next time I’m at the hangar.

I made good progress today, but still have several hours more work to do.

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I had another go at the oil temperature sender today. I used a 5/8“–18 nut to check the threads on the sender - the nut screwed on easily. A 5/8”–18 bolt wouldn’t screw into the sender hole, so I had confirmed that something in that hole was the source of my problem.

I took a strong light, did another visual inspection, and found a piece of crud in the threads, close to the top. I managed to get the debris out of the thread using a piece of safety wire, and tried the bolt again. It went a bit further, but still wouldn’t go very far using my fingers. The top thread looked a bit suspicous - partially crossthreaded.

The problem when you are fighting with a partially crossthreaded hole is that it is very hard to ensure that the thing you are screwing in the hole is perfectly aligned. I realized that I could use the 5/8"–18 nut to ensure the bolt was perfectly aligned. I held the face of the nut against the top of the hole as I screwed the bolt in. This ensured that the bolt was at exactly 90 degrees to the hole. I was able to screw it in with a small amount of assitance from a wrench. This must have realigned the damaged thread, as I could now thread the oil temperature sender in all the way using just my fingers. Problem solved.

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I spent much of Saturday out at the hangar, grinding through the various engine to airframe hookups. I’m putting things back together in the reverse order that I removed them, based on the detailed notes I took.

The biggest single thing I got done was reinstalling the oil cooler on the left rear baffle. It took quite a bit of patience to get the oil cooler hoses to screw back onto the fittings on the engine and oil cooler, but I finally got them done once I discovered the correct magic words to utter.

I ran into one significant snag, much to my frustration. The oil temperature sender would not thread back into the hole on the top of the oil filter adapter. It would screw in about one turn with my fingers, then come up hard. I tried gently turning it with a wrench, to check whether there was just a bit of crud, but it wouldn’t turn any further. The threads on the sender look good, but the ones in the oil filter adapter look suspicious.

I don’t recall any difficulty when installing this sender before, but it certainly feels like it is cross threaded now. I acquired a 5/8"–18 nut and bolt late yesterday. On Monday I’ll use them to confirm the sender threads are good, and the ones in the engine are bad. Then I’ll call Aero Sport Power to discuss it with them. They must have put a sender in that hole when they ran the engine in their test cell, and perhaps the installer cross threaded it. The oil filter adapter is a removable part, so I think the best option is to have Aero Sport courier me a replacement, and I’ll send this one back to them.