This has happened four times. To me.
The first time it happened I hadn't been a flight instructor for two weeks. I was doing touch and go landing practice at an airport just north of Vero. Shortly after take off, the airplane began running rough and lost power. I think I had somewhere around 350 hours of flight time then. This was a pretty monumental test of my ability two weeks into the job. I remember it vividly.
We had just taken off runway 8, probably around 200-300 feet above the ground when it happened. I said a very nervous "my controls!". I turned the plane around and re landed on the runway we just departed on. This plane gave power back after the initial power loss, which will prove to be the case with each. The engine never really 'fails' it just temporarily loses power. However when you fly a single engine airplane and the only thing keeping you in the air starts to sound unhappy, the effects are very scary.
The second time it happened wasn't much time after the first. About two months later I experienced this again, but this time it was in the traffic pattern in Vero. I was with a student practicing touch and go landings (I should avoid this huh?) on the small runway. We were upwind of the runway at about 700 feet, my student was just starting his crosswind turn when the engine shuddered and lost power. We were in a much better position than previously. We had altitude and the airplane was nearly pointed at the airport. Easy peasy.
The third time it happened was almost exactly 2 years after the first. It's incredible the way experience shows you the way. This time it happened at nearly 1200 feet. We had just departed from Vero and were climbing out to the practice area for some maneuvers. I took controls, informed tower that we were returning to the airport, and landed without incident. I knew the scenario, I knew the engine wouldn't completely lose power, I knew we were ok.
The last time it happened was just a short while ago.
It was more complex and time critical than any of my previous attempts.
I was on a night flight with a student. We had to complete 16 landings and fly for a little over three hours. It was going to be a long flight. We took off from Vero and after a few touch and go landings we departed to the north. In an effort to make the flight not feel like a three hour flight, we did a few landings at random airports along the way. In hindsight, I'm very happy that this didn't happen at one airport in particular.
There is an airport just to the south-east of where our evening stay was. We did a few landings here; short runway, water on one end of the runway, and congested buildings and houses on the other end. This story would read much differently if this had happened here.
Anyways, I'm getting a little ADD'ish. Focus.
We went to Titusville for some touch and go landings(hrmm). One thing to know about Titusville, they have quite possibly the largest fleet of helicopters for a flight school. The airspace is always buzzing with helicopters, day or night. This evening was no different. When we first arrived there were 2-3 helicopters in the traffic pattern. No problem, we joined the traffic pattern and began our work. Since I had to do 16 landings I was just interested in getting them over with as quickly as possible.
I think we had done 2-3 landings when it finally happened. Promptly after a touch and go at or around 100-200 feet the engine shuddered, began running rough and lost power. This was a new place for me. I have almost 2000 hours of flight experience, yet only 150 hours at night. Night time alone adds a dimension of difficulty, yet an overcast layer of clouds blocked the moonlight. It was dark.
I immediately idled the engine power and pushed the nose down to look in front of the plane. All I really noticed ahead of the airplane were the red lights telling me where the end of the runway is. I didn't have enough runway ahead to stop the airplane safely. I looked to my right and saw another runway with plenty of distance for me to be able to stop the airplane. I hesitated for a moment. Taxiing across that runway was a helicopter. Here I was at night, trying to re land an airplane over a helicopter. If this were a movie, John Woo would be the director and this next part would happen in slow motion with explosions in the background.
I looked back in front of the airplane again to be sure there was no way I could possibly just land straight ahead. Oh no. Those red lights just got a lot closer. I wanted to say something on the radio to warn the helicopter to move his butt off the runway. My mouth wasn't ready to speak yet. My brain power had been diverted to my hands and feet flying an airplane. I made the turn to the crossing runway, which was 90 degrees from the runway I took off from(departed an east runway, landed on the south runway).
"two zero victor landing 18!"
It was an excellent landing. Intense focus and adrenaline really make for great landings.
I taxied clear of the runway and stopped and ensured my students were still breathing. I have to say, every single student that was sitting in the left seat when these four events occurred, really took it well. As a flight instructor you always hear horror stories of students that will lock up on the controls, panic, or puke. Those are three things you never want a student to do. All my students just sat back, didn't say a word and watched it all unfold.
I knew what happened was more than likely fouled spark plugs, and I knew that the likeliness of it happening again that night was extremely rare. However I was not comfortable leaping back into the air at night to possibly have to attempt this again.
We use AVGAS that has an octane rating of 100. Specifically we use 100 low lead. Now even the name is a lie, because this 'low lead' fuel has a lot more lead than your run of the mill unleaded fuel. Lead is an additive that works really well in preventing engine 'knocking' or technically known as detonation. Essentially when an engine burns fuel it is desirable for it to smoothly burn in the precise cycle of the engine. When it instead explodes it creates engine 'knocking' and can seriously damage an engine. Unfortunately lead works the best for this.
Now speaking to aviation, the lead content is there for the same reason. Even though it's considered to be 'low lead' enough exists to create problems. This is exacerbated by Florida's heat and humidity. Warm air is less dense, which creates an excessively rich fuel to air ratio. This means a lot of unburned fuel is left in the cylinders during combustion, this in turn leaves lead deposits in the cylinder. Now if you paid attention in chemistry you would already know that lead doesn't conduct electricity well. SO essentially what happens, over time lead builds up and can get caught in the spark plug. Now most of the time the lead is just ejected from the cylinders by the exhaust valve, but sometimes, when you get REALLY lucky they stay. Even luckier, stuck in the spark plug.
This essentially kills the cylinders power, and an engine is all about balance. When one cylinder stops producing power it really messes with the rest of the engine. This is what causes the shuddering and the engine roughness.
The lessons learned from these four events are very diverse for nearly being the exact same event. Every time this problem presented itself it was due to fouling of spark plugs. I hope one day when the engine actually fails, loses complete power, or just stops, I will be as ready for it as I was with these.
Through it all I learned to be patient, aware and always looking for the next spot to land a disabled airplane.