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Things That Come in Threes
Two partial engine failures and a fuel valve problem
By Mike Davenport
January 2020 - It was an interesting year from the standpoint of gaining new flying experiences. During the course of the year, I had to deal with three partial engine failures, one due to a faulty fuel valve (and poor preflight procedure) in a friend's Citabria, and the other two from valve failures in my Stinson. Fortunately, each event ended safely at my home field.
The first was early in the year towards the end of a local sightseeing flight over the nearby mountains. After my descent back into the Fraser Valley, I had flown over to Delta Airpark to check the condition of the grass runway. It looked a little too wet, so I decided not to stop and instead headed back home to Langley.
It was a nice day and I stayed low (avoiding any built-up areas), following the shoreline of Boundary Bay. All was perfectly normal as I began a climb up over a trestle and a local ultralight field. At about 800 feet, the Franklin went rough. Very rough. Carb heat and switching to a different tank had no effect. The vibration was so severe that I thought I might have lost the tip of a prop blade. Reducing power didn't help. In fact, the engine would only run, after a fashion, with full throttle.
I had continued towards home while all this was going on. I called the tower and advised them that I might have to make a forced landing en route. As I proceeded, trying to get the engine's shaking in cycle with my own, I noticed that I had been able to climb a bit. This created a number of options, not the least of which was the possibility of actually getting all the way home — far more preferable to landing in a wet, snow-covered pasture. Gaining confidence, I overflew Geordies Field, another possible landing spot, and requested a straight-in approach to 07, our grass runway.
The tower by this time was prepared to give me anything I asked for, including the "equipment." I set up for final approach and then had to slip off a lot of extra height. While on short final, the tower felt obligated to tell me I was making smoke! Somehow, that seemed like too much information right then and I didn't respond. As I crossed the boundary fence, I closed the throttle completely and the engine quit. I made the quietest, smoothest downwind landing I have ever done. One tends to focus during those moments.
I had enough momentum to roll clear of the runway, and after coming to a halt, once again called the tower, thanking them for their help and advising them that I'd be getting a tow back to my hangar. I contacted a friend, and he brought his truck and a towrope, and we were able to get the Stinson back to the hangar for the post-mortem.
Opening the cowling revealed the source of the smoke. A valve cover had developed a large hole, and oil spewed out of it and covered the inside of the cowling, the engine, the firewall, and the exhaust system. As I had no tools in the hangar that day, and needed some time to settle down anyway, I decided to leave the rest of the inspection until another time.
The next day, after removing the offending cylinder, the problem was identified. The intake valve's keepers had let go and the spring drove the retainer through the valve cover, bending the rocker and trapping the spring over the rocker arm. The valve got drawn down into the cylinder, breaking it into three pieces, punching a hole in the piston and another right through the cylinder. Parts of the valve stem ended up in the intake manifold. Of course, the cylinder was ruined.
Three months later, everything was finally all put back together, with an overhauled cylinder. A period of run-ups on the ground checked out okay, so a half-hour flight was flown directly over the airport, just in case. That all went very well. After landing and checking for leaks, I decided to put some running time on the engine by going to Chilliwack for lunch. Since my engineer had some slack time, I offered to buy him lunch as well.
We climbed out of Langley and headed for Aldergrove, towards his home to see if his wife was out in the garden. She was, and just as we got overhead, we sure knew how to get her attention. The Franklin swallowed another bloody valve! This time the issue was in the next cylinder. The roughness was familiar, so no time was wasted fiddling with either fuel or carb heat.
I called the tower and they gave me the requested straight-in to another downwind landing with no discussion. This time when I pulled the power off, the engine didn't quit and held at around 1500 rpm. This I didn't need, what with the tailwind and all, so I killed the mags and did my second dead-stick landing of the year.
This time an exhaust valve came apart right at the "tulip." My engine guy in Portland had never seen one like it. The valve head rattled around in the cylinder and then got rolled up and jammed into the head of the piston. The piston cracked and jammed in the cylinder and had to be driven out later with a hammer. The wrist pin and con-rod could not be disassembled due to the wedging of the valve head.
Well, that was enough of that. The engine went out to be majored.
The fuel problem is a little embarrassing, as it involved a preflight done without using a checklist — in a borrowed plane.
Another beautiful day and I convinced my wife, who was not big on the idea in the first place, that we should go flying to look at the tall ships in a nearby harbour. I had recently been checked out in my friend's Citabria and had the loan of it for the afternoon. The Stinson was down, waiting on a rebuilt engine (see above).
I did a thorough walk-around, checking fuel and oil, moving all the bits that are supposed to move and trying to move some that aren't. Once inside and buckled up, l started the little Lycoming and let it warm up while I checked the ATIS and got taxi clearance. A normal run-up followed, and I taxied to the active and backtracked to the end.
I pushed the throttle to full power and began the takeoff roll, and it all was so darned normal until I got airborne. The engine began to miss, cough, catch, sputter, et cetera, and we weren't climbing. If this has ever happened to you, you know it is not a good thing. I was able to maintain about 300 feet and minimum flying speed with the engine alternately surging and quitting.
I called the tower (for the third time this year) and they cleared me to any runway. I managed to complete the never-to-be done turn back to the departure runway by using rudder only to flat turn, avoiding any stall-increasing bank. However, when the runway came into view, there was a Bellanca about halfway down its 2000-foot length. So much for that idea! I continued the right turn towards a hay field that had some potential if the engine had quit altogether. All through this epic, the Citabria is pitching up when it got fuel and sagging down when it didn't. I went past the tower, around the barn, and landed to the west on the grass runway.
Once on the ground, the engine ran normally. We taxied back to the hangar, and I tried several full power run-ups and everything seemed fine. I shut everything down and tried to figure out what had happened and why.
As I looked around the cabin, it soon became clear what the problem had been. There, under the left side of the panel, was a fuel valve firmly in the "off" position. It seemed very tight when I turned it on, but it did move, slowly. I restarted the engine and did another run-up and everything seemed to work fine. After convincing my very brave wife that everything was okay, we again took off and had a very enjoyable hour-long sightseeing trip.
Further investigation showed that the factory swivel connection at the fuel valve had been replaced by a homemade part sometime in the aircraft's history. The valve had become stiff, as they do with age, and this bogus fitting had bent. The bending, combined with the stiffness, resulted in the valve not shutting off completely. This allowed enough fuel for a run-up and taxiing, but not enough to sustain takeoff power. Had the valve shut off properly, the engine would have started but run out of fuel before I got to the run-up bay, thus alerting even me that something wasn't quite right.
Two previous owners had never used the fuel shut-off, and of course had never had a problem, as the valve was always full on. The current owner was in the habit of shutting off the fuel. He had previously owned a Champ and shut the fuel off after each flight due to a leak through the carburettor. I have never shut off the fuel in my Stinson and never even thought about the valve. However, had I taken the time to use the printed checklist stashed up high on the right side of the cabin, none of this would have happened.