Our minds crave excitement and stimulation, but we can’t sustain high levels of excitement for prolonged periods. Following minutes of high-intensity stimulus, our minds want to relax. As we enter this psychological letdown state, we lower our guard against potentially surprising or startling events. Because of this, the shock effect is stronger. The startle effect is intensified and it takes us longer for us to recover from disruptions. Film makers exploit this effect in their plot lines. After a high-energy chase scene, they insert a low-intensity lull. As our minds sense that the exciting part is over, we relax our tense shoulders, sink back into our seats, grab another handful of popcorn, and lower our guard. Then, film director hits us with an unexpected zinger. It really shocks us.
As pilots, this psychological effect can emerge following any high task-loaded flight segment (like shortly after takeoff, after landing, or following an intense inflight event). Let’s examine a typical example of a taxi-in event following a challenging approach and landing. As professional pilots, we are quite skillful at raising our attention level to cope with the challenges of a difficult approach and landing in adverse conditions. Bumping down a turbulent final, concentrating our instruments, we feel rewarded to see the runway lights emerge from the gloom. We land, slow down, exit the runway and immediately feel the urge to relax. We did it. We made it in. We unknot our shoulders and sit back in the seat while anticipating a routine taxi-in to the gate.
The speed at which we can settle into this relaxed state seems to be related to our experience level. The more flight time we have and the more proficient we have become, the easier it is for us to relax following a challenging approach. When we combine this with expectation bias (expecting a non-challenging taxi-in), the stage is set for us to make an error, miss an error, or fail to recover quickly from a disruption. Following is an example event from a B-787 crew reported in the NASA ASRS program (report #1998466).
Captain’s report: After landing Runway XL uneventfully, I exited runway and began taxiing as instructed by ground control. While beginning a slight left turn I noticed the aircraft didn’t respond to my tiller input. I applied brakes and the brakes did not actuate. I looked up at the hydraulics switches and noticed they were turned off. I called out to turn the hydraulic pumps back on and the First Officer complied. Once the pumps were activated, the brakes and tiller began to work again. The First Officer apologized and said he had a “brain fart”. The nose wheel crossed the double yellow line and towing was required. There was no aircraft damage and no taxiway lighting or equipment damage and there were no injuries.
First Officer’s report: Ferry flight from ZZZ1 with no passengers – upon turning onto Taxiway X after landing at ZZZ, the First Officer inadvertently turned off the hydraulic pumps prior to the southbound turn. Upon realizing the error, the pumps were turned back on, but not before the nose wheel was outside the double solid line. There were no injuries or damage.
While this report doesn’t say, it is likely that the crew used engine anti-icing on final. Exiting the runway and experiencing a natural psychological letdown, the FO probably mistook the hydraulic switches for the engine anti-ice switches (identically shaped and colored switches on an adjoining panel) and turned them off instead. The error should have generated a Master Caution warning light, but their report does not say. If so, we can add that to the list of indications missed during their psychological letdown. Additionally, the Captain appeared to be a bit slow to recognize the FO’s error as the aircraft veered off of the taxiway centerline. Luckily, they recognized the cause and got the hydraulics on in time to prevent a taxiway excursion. Unfortunately, they still required tow-in because they felt that they were too close to the taxiway edge to maneuver safely back to the centerline.
Other errors that can occur during this vulnerable relaxed state are taxiway clearance errors, configuration errors, and distraction events while performing discretionary flightdeck cleanup tasks. We rarely attribute these events to psychological letdown following high task loading flight segments. In the end, our human minds remain vulnerable to mental vulnerabilities. We each should study this effect in ourselves and within our safety programs. Following your next challenging approach, notice if you have a tendency to relax perhaps too quickly or too much. Within our safety programs, see if we have a rise of error events following intense flight phases. I predict that we will discover that this is a worthy topic for self reflection and a continuation training module.
