Honey, I Think We've Lost Our Spark

Expect the Unexpected

By design, $100 hamburger runs rarely involve much adventure beyond the expected aviating. Sometimes, additional adventure -- perhaps "excessive adventure" -- finds you anyway.

Keen(e) to Explore

Date	Aircraft	Route of Flight	Time (hrs)	Total (hrs)
09 Apr 2024	N21481	SDC (Sodus, NY) - RME (Rome, NY) - EEN (Keene, NH) - SDC	5.0	2795.7

Aloft on a rare weekday off from work, I proceeded eastward toward New Hampshire through smooth air devoid of clouds. I set Keene as my destination, finally making good on a months-long goal to try out Mama McDonough's Irish Pub located in the airport terminal. I made a quick stop at Griffiss International (RME) for fuel before proceeding to Keene. At $5.24/gal, they were practically giving their fuel away. (Well, not actually true, but many places are $6+/gal right now.) Aside from some of the typical glitches in communication between air traffic control and other pilots, including my participation in a relay from Syracuse Approach to another aircraft, nothing noteworthy occurred on the outbound flight. Crises are often preceded by the mundane.

Crossing the "Green" Mountains of Vermont

Closer to Keene (more properly, "Dillant-Hopkins", #273), I was surprised by the amount of activity buzzing around the airport. I sequenced myself into the traffic flow for Keene's 6200 foot long runway 2 where multiple aircraft were holding short waiting for airborne traffic to land. One aircraft scooted out while I was on final and, though I was dubious about this choice, the pilot expedited his departure and was airborne well before I touched down.

Keene's terminal is located on the far north ramp, requiring a significant taxi relative to most uncontrolled fields I frequent. Other transient airplanes parked on the ramp indicated that I was not the only Tuesday arrival for lunch.

Mama McDonough's occupies the eastern end of the terminal building that is shared with the local FBO, Monadnock Aviation. Beyond the pub's unassuming entrance, a line of patrons were waiting to be seated. It was obviously a popular place.

As I waited, I noticed that the day's special was buy one / get one burgers. Should have brought a friend. Regardless, I was at an Irish pub and that usually inspires me to order fish and chips.

Two waitresses worked the room. While busy, they were friendly and efficient. From my seat, I had an excellent view of the ramp and the comings and going of piston and turbine aircraft alike. Partway through lunch, a large turbine aircraft taxied onto the ramp and swung its rear end around to point at the little airplane tied down at the opposite end of the row of parked aircraft that included Warrior 481. Caught in jet blast, the small two seater danced and swayed to the extent that its tie down ropes permitted. It was a demonstration of poor manners from the jet crew and I was grateful that it was not my airplane on the receiving end of the jet wash.

My fish and chips were delicious; my Scottish grandmother would have been pleased. When I cut into the lightly breaded deep fried haddock, I found the fish inside to be perfectly cooked and remarkably moist. Onion rings included among the chips were a nice touch. Excellent food, great service, and a view of the airport ramp made for a terrific lunch experience.

When I returned to the ramp, the piston aircraft had completely turned over since my arrival. Not bad business for an airport diner on a Tuesday.

Taxi Slog

The north ramp at Keene was quite a bit more "turbiney" than most uncontrolled airports I visit.

Though I saw no notifications of this in official FAA sources, a sign near the terminal proclaimed runway 2 as the preferred calm wind runway. In resignation, I made the long taxi from the north ramp back to the departure end of runway 2. I have taxied shorter distances at much larger commercial international airports. 

Drafty

Warrior 481's power plant ran up normally and I departed Keene satisfied with another successful visit to a new airport. Climbing northbound off runway 2 with the town of Keene directly below, I turned westbound as soon as I judged myself well positioned to outclimb the foothills of the mountains immediately west of the airport.

It was unusually breezy in the cockpit, but I focused on flying the airplane until I turned on course and pitched the nose down a few degrees to enter a cruise climb. My troubleshooting was brief. The top latch on the door had come undone. My last experience with this was in a rental Cherokee 180 (N3470R) back in Michigan. Reduced static pressure in the slipstream pulled the door outward just enough that I could not engage the latch. I had two options. I could return to Keene and latch it on the ground or I could wait until I leveled off and put the airplane into a slip (fly it slightly sideways) to push the door closed so that I could latch it in flight. I have never tried the latter and had no practical experience with the technique, only that it should work in principle.

Amusingly, I told the story about Seven Zero Romeo's top latch popping open with Kristy on board recently over dinner with friends. I had bragged to that audience that Warrior 481's door has never popped open in flight during twenty years of ownership. While I guess that boast is still true, I had to eat a little crow with Kristy when I returned home and told her about the incident at Keene.

Crossing through 2,500 feet with the foothills now passing beneath my wings, I was considering my options for dealing with the door when the entire airplane began shuddering as though trying to tear itself apart. Thoughts of the door were promptly relegated to the back burner.

Shake, Rattle, and Roll

The only time I had ever observed such rough engine operation was the one time I experienced carburetor icing in the Warrior. Without even thinking about it, I turned on the carb heat and waited a moment, but nothing changed. I pushed the nose down to a level flight attitude and pulled the throttle back. The roughness ceased below 1300 rpm. I pulled the throttle to idle, pushed the nose down to maintain airspeed, and rolled the airplane back toward Keene. In the turn, I noticed that the JPI engine monitor showed zero temperature reading on cylinder #1. This meant that it was not generating any power.

That explains the roughness. Four cylinder engines don't like running on just three.

"Keene traffic, Cherokee Four Eight One is two miles west and returning to the airport with a rough engine." 

A Mooney inbound for the pattern immediately yielded the right of way to me. I glided back to the runway without any difficulty and actually had excess altitude that I needed to bleed off with a massive forward slip prior to touching down. 

Foreflight ground track showing the departure and immediate return to Keene.

At taxi power, the engine ran smoothly and I vacated the runway. Once on a taxiway, I tried to run the engine up again, but the airplane shook violently when I advanced the throttle above 1300 rpm. In taxiing from the terminal to the departure end of runway 2 just a few minutes earlier, I noticed Monadnock Aviation's maintenance hangar on the northeast ramp. I shut down there and called Ray. He was concerned that I had a stuck valve, but we decided that I would consult with the on field mechanics to see what they could discover.

Benchmark for Customer Service

I wandered into the tidy shop and met Tim and Warren of Monadnock Aviation who listened to my story. Warren explained that, before they could look at my plane, I needed to work out an arrangement with management back at the main terminal building. I called over there and was eventually connected with Beth, a Rochester Institute of Technology grad who was in charge. At her prompting, I described the incident again.

"OK. But first, how are you?" she asked.

"I'm fine." My heart rate wasn't even up.

"Pilots react differently to these situations, so I just want to make sure that you're OK."

"Thanks for asking, but I'm OK." It was thoughtful of her to ask. Once that was out of the way, Beth was all business.

"They're pretty busy right now, but they can probably do some troubleshooting. I cannot guarantee that they will be able to fix whatever is wrong today." 

I understood completely. How could she make any promises without knowing what the problem was? Once she verified my understanding, she asked to talk to one of the guys in the shop. I handed my phone over to Warren so that she could speak with him.

After some additional bureaucratic steps, Tim pulled the Warrior into their hangar. He immediately removed the valve cover on cylinder #1 to check for a stuck valve, but as he turned the prop, the valves moved as expected. It was not a valve problem.

Next, Tim pulled the bottom spark plug out of the affected cylinder. "Well, I found a problem," he declared and handed the spark plug to me.

Broken spark plug.

The ceramic insulator near the electrode was in pieces. When he checked the top spark plug in cylinder #1, it was badly fouled. Despite the redundancy of two spark plugs per cylinder, both plugs in the same cylinder had failed in different ways. What are the odds of that?

Tim replaced the broken spark plug and asked if I wanted him to clean up the other one or replace it as well. I suggested cleaning it first. Tim retreated to the rear of the shop to work on the plug. When he returned, he commented, "It makes a spark now, but it's not a great spark. Keep an eye on it, you might want to replace this one, too."

Tim wrapping up the spark plug replacement on cylinder #1.

With the repair complete, I taxied the Warrior to the edge of the ramp and performed a run-up. The engine ran smoothly regardless of whether I ran on both ignition systems or either individual. Tim printed up a log book sticker for me and sent me back to the main terminal to settle my bill. "They don't let me handle any money," he indicated with a shrug. The total came to $160, not bad for some time and materials. My experience with Monadnock Aviation was the exact opposite from my experience at Columbia County Airport in 2012 when I suffered a carb fire and was presented with a four-figure invoice for essentially no real work. Huge thanks to Tim, Warren, and Beth for their prompt, professional assistance. As a friend of mine later summarized about the entire incident, "It was the best worst thing that could have happened."

After paying my bill, I was taxiing back to runway 2 when another aircraft on frequency called me. "Hey, Four Eight One, what happened to your engine?" I explained the dual spark plug failure and thanked the unknown pilot on the other end of the radio for his concern.

Aftermath

Warrior 481 underwent another successful run-up as I worked through my departure check list. Not forgetting the contemporaneous door issue, I double checked the door latch before throttling up to take the runway.

The engine ran well. The cabin remained free of drafts. I climbed back over foothills of the mountains and ultimately to 6,500 feet for the ride home.

JPI EDM-700 display showing high EGT on cylinder #1.

While the engine ran palpably well, the engine monitor still indicated an issue in cylinder #1. Normally, my exhaust gas temperatures (EGTs) run close to the same value. But EGT on cylinder #1 was running hotter than the others by 170-200 degrees. High EGT usually indicates an inefficient burning of the air/fuel mixture causing a delay in combustion that means less energy is used on the power stroke and more energy is lost through the exhaust valve. EGTs increase during magneto checks for the same reason with each cylinder performing less efficiently on a single spark plug than it normally does on both. Cylinder head temperature (CHT) on #1 was commensurately low.

Tim's comment about the cleaned spark plug not yielding a great spark came back to me. I had that spark plug replaced the next day and in subsequent flights, EGT on #1 has been in line with the others.

So, What Happened?

I am puzzled by the fouled plug. I am very rigorous about leaning my engine, even during taxi, to avoid loading up the plugs with carbon. Did I do so during the long slow taxi from the terminal ramp to the departure end of runway 2 at Keene that day? I could not recall. When I expressed my surprise about the fouling to Tim, he concurred. "Beyond that plug, it looks really clean in there," he noted.

As for the broken spark plug, I only know of two possible root causes for that. Either plugs get dropped / damaged during maintenance and fail later in flight or they experience a detonation event.  Given the successful engine run-up and initial smooth climb away from Keene, it is obvious that the plug failed in flight. I am reasonably certain that no detonation occurred while operating with a full rich mixture in the climb. In real time, I saw no evidence of the whopping temperature spike that would have accompanied detonation and the JPI did not squawk any temperature alerts as it is programmed to do. (And has previously). The most impartial arbiter of what really happened before that cylinder went cold would be temperature data logged by the JPI engine monitor. After multiple download attempts and a consultation with JP Instruments, it appears that the device stopped logging data at some point. I am in the process of working through a fix with JP Instruments, but frustratingly, those data from Keene are lost forever.

Regardless, I put 4.5 hours in local flying on the engine prior to my next trip and observed completely normal operation that provided confidence for the next adventure. In the end, even though it was "buy one / get one burger day" at Mama McDonough's, I am glad that I did not bring a friend with me on the flight to Keene. Sometimes, we get a little more adventure than we need.