Two useless engines

I have had several engine failures with twin Cessnas, and the second engine always got me safely to an airport. This safety advantage is partly because the two engines are completely independent of each other, so that nothing that happens to one will affect the other. There is the chance of fuel exhaustion or fuel contamination affecting both engines, but at least mechanically and electrically the two engines are completely independent. Multiengine pilots take some comfort that both engines failing simultaneously is pretty much impossible. Or is it?

One Saturday morning I was to reposition a Cessna 421 to another airport for the owner for a reason I cannot recall. This aircraft was leased to my company for Part 135 charter operations. This Saturday I was doing a preflight of the aircraft and noticed something questionable on the right engine. Fortunately, my director of maintenance was in his office that day, probably catching up on administrative work, so I took advantage and had him take a look. In the process, he wiggled the spinner, and the entire propeller assembly moved up and down significantly. The aircraft not being flyable, we removed the cowling and found that the gearbox was fractured. If the aircraft was flown, the entire propeller assembly may have separated from the engine. It seems incredible luck that it did not separate on the previous flight.

The aircraft owner, after being told the bad news and after some research on options, decided to buy a factory remanufactured engine to replace it. About a month and a half later, the big day came to do a test flight and initial engine break-in. I departed the airport and proceeded to a practice area not far from the airport. It wasn’t long before I noticed some engine vibration on the left engine. (The reman engine was on the right.) Since the engine was still developing some power, I did not feather, but rather reduced power. I headed back to the airport and declared an emergency. On the downwind leg, the control was becoming a bit questionable, so I feathered the left engine at that point, and continued for a successful landing.

When I declared an emergency, the airport claxon sounded, and my director of maintenance was having anxiety attacks, wondering if he had done something wrong on the new engine installation. He was relieved when he saw it was the left propeller that was feathered.

During the post-mortem of the failed engine, a broken bolt was found for one of the rocker arm valves. There was some discussion of doing a metallurgical analysis of the bolt, but that idea was discarded when it was found that most of the rocker arm bolts on the other cylinders were under-torqued. It was apparent that the bolt had slowly worked its way loose and then was exposed to stresses it was not designed for. The under-torqued bolts occurred long before we leased the aircraft and before our DOM was maintaining it.

All this is to demonstrate that at the time of my contemplated reposition flight, both engines were at risk of imminent failure for two completely different and unrelated reasons. My flight was fairly short, so maybe I would have made it, or maybe not. If I had made the flight and experienced double engine failure, I can imagine the NTSB report would have been unique, elaborating on the engine teardowns showing two unrelated faults.

I don’t have any explanation about how the planets seemed to have aligned to make that situation. But I have also thought a lot about how things worked out that I did not make that flight. I just happened to notice something that made me want to get an opinion. My director of maintenance just happened to be working that day to help me out and discover a fatal problem in the process. I know my mother has always prayed for me every day for protection and guidance, and I can’t help but feel that those prayers were a big reason that someone was looking out for me that day.

After all that, do I still believe a dual engine failure is highly improbable? Believe it or not, yes. Some might say that since I have my once in a thousand lifetimes event over with, I don’t have to worry about it anymore. But I don’t buy that either. One thing I take away from it, though, is that when buying or leasing used aircraft, you don’t really know for sure what you’re getting. I probably have an additional degree of conservatism in my flight operations and decision making that I didn’t have before. Engine failures can occur with no warning. But at least pay attention when you see, hear, or feel something that doesn’t seem quite right.

Ken Smith is a CFI and ATP with 9,000 hours and 40 years of flight experience. He owns a Cessna 310 and Cessna 421 Golden Eagle.