A case of multiplying mistakes
We were cruising somewhere over east-central Georgia on a northerly course, above the clouds, negligible headwind component, engines running smoothly, back-seat passenger comfortably reading her book, and on track to our destination airport. Life was good, but about to get busy.
I was monitoring the clock, preparing to switch from the auxiliary fuel tanks to the mains. The pilot-friend sitting in the right seat had been flying for about an hour. I was taking him and his wife to a small airport in North Carolina to pick up an airplane that he had recently purchased.
Suddenly, the right engine began to surge. Following an instantaneous but seemingly interminable moment of frozen denial, my brain snapped to attention and immediately identified the source of the problem, and the cure. I reached for electric fuel pump toggle switches on the instrument subpanel and flipped them up to the On position. Next I reached down to the fuel selector handles located on the floor between the two front seats and switched the right tank from the Aux setting to Main, then did the same for the left tank.
The right engine continued to surge for a few seconds, and then settled down to a high-pitched buzz - too high. I checked the rpm gauge for the right engine and saw that the needle was headed past the 2,700-rpm redline.
"Your airplane," the right-seater barked. I took control of the yoke, then grasped the propeller control lever for the right engine and pulled it back. This should have increased the pitch of the blades and thus reduced propeller and engine rpm. Instead, there was no response. The engine and prop continued to wail in uncomfortably high-pitched harmony.
I pumped the lever forward and aft without effect and then resolved to attempt to shut down the engine. I had to act quickly to prevent an overspeed, which potentially could lead to catastrophic failure of the engine and/or propeller.
Just as quickly as I made the decision, the whining subsided, and the engine and prop settled back down to a safe rpm. I adjusted the prop control to set 2,400 rpm and took a deep breath.
The entire episode had lasted no longer than 10 seconds, although it seemed much longer. My first reaction after the excitement subsided was confusion. The engine and propeller rpm problem were a result of the initial engine surging, which occurred because the right auxiliary tank had run dry. But why had it run dry? The answer dawned on me, and bewilderment turned to embarrassment. To badly mangle Pogo's words, I saw the problem, and it was me.
As is my custom on long cross-country flights, 30 minutes after takeoff I switched from main to auxiliary fuel tanks. I knew from experience that at our 9,000-foot-msl cruise altitude and best-economy fuel-flow setting, we could fly for an hour and 45 minutes on the aux tanks before switching back to mains and still have a small reserve in the aux tanks. I'd done it many times when maximum range and endurance were the objectives, as was the case on this flight.
In reviewing the flight, I identified two mistakes that led to fuel starvation of the right engine. The first was busting the one-hour, 45-minute limit on aux tank use before switching back to mains. I was fixated on the clock in order to make the switch at the precise time, but with just a minute or two to go, something - I don't remember what - distracted me. The result was that the deadline for switching tanks came and went while my attention was diverted.
That moment of inattention could not have been the only cause of the tank running dry, because there should have been enough fuel in the aux tanks to last for at least another 10 minutes. It was the combination of that mistake and one I made early in the flight that clinched the fuel starvation outcome.
The day had begun with an 18-minute repositioning flight south to pick up my two passengers. During the cruise portion of the short leg I switched from the main fuel tanks to the auxiliary tanks for a few minutes. It couldn't have been more than 10. After landing I made a precautionary visit to the bathroom, then the three of us got in the airplane, fired up the engines, and taxied out for takeoff and a nearly 3.5-hour nonstop flight north.
My friend, who is a professional business- jet pilot, was just getting back into flying light airplanes. This was his first time in mine, and after we leveled off at our cruise altitude he began asking a lot of questions about fuel consumption, range, and endurance. We reviewed the distance to the destination airport, fuel remaining, endurance, winds, and en route and destination weather. Based on my calculations, we should have been able to fly nonstop and land with more than IFR reserves.
Satisfied, he accepted my invitation to handle the controls. An hour later the right engine began sucking air.
I had goofed, but where? It was the repositioning leg. When calculating how long we could fly northbound on the aux tanks, I failed to account for the southbound portion. That was the missing 10 minutes of fuel.
Dumb mistake? Sure it was, but when combined with the second mistake - allowing a distraction to divert attention from switching fuel tanks on schedule - it became something more.
A lapse in attention or concentration is nothing unusual, no matter the activity. A recreational golfer who suffers one on the tee might write it off as a Mulligan and take another poke at the ball. Unfortunately, pilots don't get to take a Mulligan. Mistakes count and, worse, they may compound.
We try to avoid making mistakes in the first place, but they do happen. The next best thing to avoidance is recognizing when a mistake does occur, and making sure it is not followed by more.
Mark Twombly is a writer and editor who has been flying for 35 years. A commercial pilot with a multiengine rating, he is co-owner of a Piper Twin Comanche.
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