By Robert N. Rossier, EAA 472091
This piece originally ran in Robert’s Stick and Rudder column in the May 2025 issue of EAA Sport Aviation magazine.
The run-up was okay, but just barely. The magneto check was right at limits with a 150 rpm drop. While it wasn’t as good as I would have hoped, it was still, by definition, not enough to ground the airplane. I figured it was likely just a spark plug that needed cleaning or replacement. Only later would I learn how closely I had navigated to a serious failure.
The aircraft preflight inspection and pretakeoff run-up are often our last chance to find problems and avert an in-flight emergency. As such, we owe it to ourselves and our passengers to perform these preflight activities and flight procedures with the greatest degree of care and objectivity. Should we miss a sign that something is awry, we could easily be missing an opportunity to avoid flying headlong into a dangerous situation.
Creeping Complacency
One way we miss opportunities for avoidance is through complacency. Especially when it’s cold, dark, or we’re in a hurry, we might be tempted to skip a step in the process, particularly one where we’ve never previously found anything amiss.
Consider the situation where a pilot has just completed a flight, shut down the engine, let off a passenger, and then jumped back in to make another leg of the day’s journey. Nothing was wrong with the airplane during the flight that was just completed, so the pilot might be tempted to just do a quick mag check and then be on their way. But the fact of the matter is that an issue can develop at any time, and just because there wasn’t an overnight wait between legs doesn’t mean something could not have changed since the beginning of the previous flight. So perhaps we owe it to ourselves to run through the entire checklist before firewalling the throttle and launching ourselves into the wild blue yonder.
Another place we see complacency creep into our flight operations is during the preflight. A few years back, a Cessna T210 crashed due to fuel exhaustion. According to the NTSB report, the pilot stated that he performed a “standard” preflight check before departing for the 1.5-hour cross-country flight. He reported that he checked the fuel gauges and visually inspected the fuel levels in the tanks and estimated the airplane had about 70 gallons of fuel for the flight.
According to the report, “The airplane’s fuel tanks were topped off about 3.5 flight hours before the accident flight departed; no fuel had been added since that time. With full fuel tanks, the accident airplane’s expected endurance was about 4.8 hours of flight time. Thus, it is likely that the engine lost power due to fuel exhaustion.”
Whether it was the “standard” preflight procedures or the flight planning, it would seem that complacency may have crept into the process, ultimately leading to the accident.
Expectation Bias
Another way we can miss opportunities for avoidance is by perceiving what we expect to see. This might help explain what happened with the T210 crash. Just as we might hear a clearance that we expect to hear (expectation bias), the same might occur when we’re performing our airplane preflight inspection or performing our pretakeoff run-up.
For example, with a quick glance in the fuel tank, it’s easy to be convinced it is pretty much full, or at the level we expected it to be based on the last time it was filled and how much we recall the airplane had been flown. But the only way to be certain is to physically check the fuel level.
Another example of expectation bias is when we expect a pilot to be somewhere or do something. We’ve all experienced the situation when a pilot reports being, for example, 6 miles east of an airport when they are actually 6 miles west. But sometimes a pilot will fly a pattern either much larger or tighter than we expect, surprising those around them. Or, we might expect them to initiate a takeoff or quickly exit a runway after landing.
When events don’t unfold as we expect, the margins of safety can quickly erode. We can’t control what others do, but we can try more diligently to manage our expectations.
Normalization of Deviance
Yet a third way to miss opportunities for avoidance is through a phenomenon referred to as normalization of deviance. This occurs when we frequently see a condition that is marginally out of tolerance, but we operate in that condition with little or no consequence. We begin to accept the condition as “normal” or inconsequential.
In her 2016 book, The Challenger Launch Decision, sociology professor Diane Vaughan explains how this phenomenon, in part, led to the Space Shuttle Challenger disaster in 1986. Several shuttle flights had occurred where the O-rings that seal the joints along the length of the solid rocket boosters became eroded in flight. When it first occurred, it was recognized as a problem, but after a while, the perceived risk may have been diminished because it occurred on nearly every flight. It was almost considered “normal.” But on a freezing January morning, the failure of a brittle O-ring allowed fiery hot exhaust gases to escape, damaging the structure and ultimately causing the external fuel tank to explode. The shuttle and its seven-person crew were all lost.
As pilots, we should be aware that normalization of deviance can also sneak into our decision-making process. When we see something that is not quite right but is observed frequently, we begin to see it as normal. We no longer associate the problem with the potential danger it represents. Loose or missing fasteners, a switch that doesn’t always work properly, inaccurate instrument readings, fuel stains, a seemingly minor crack in a windscreen or skin, corrosion, a minor oil leak, or a radio problem. Such conditions — seen over and over again — might cause us to perceive them as normal or inconsequential. We no longer internalize the risk represented by the deviant condition. But “normal” is not always safe.
Lesson Learned
Other pilots flew the airplane later that day, but the next day, the marginal mag drop was brought to the attention of the mechanic. After checking it out, our mechanic determined that there was indeed a serious engine problem. The mag drop was one sign of an issue. The mechanic also noted that the engine wasn’t running as smoothly as it should and had developed a significant oil leak. The root problem was a stuck exhaust valve, which had caused the pushrod to bend and the leak to develop.
The next phase of the evolving damage could easily have been an engine failure. If the rough mag issue had been investigated earlier, the root cause could have been identified and engine damage limited.
I may have dodged a bullet that day. In retrospect, I should have been leery of the mag drop that hung on the edge of limits. I should have questioned it further and had a mechanic look closer, rather than letting it slide. The incident serves to highlight the need for all of us to realign our perspectives on what is normal to maintain a questioning attitude, and ward off complacency that can creep into our daily flying routines.
Robert N. Rossier, EAA 472091, has been flying for more than 40 years and has worked as a flight instructor, commercial pilot, chief pilot, and FAA flight check airman.