December 8, 2016

Accidents: The pointy end of the spear


Accidents: The pointy end of the spear

Last month we investigated the preconditions for unsafe acts that lead to accidents. We talked about the operating environment, personnel factors and the condition of the pilot that potentially impact a flight operation; leading to the commission of unsafe acts.

The concept is a simple one; absent or deficient defenses against committing unsafe piloting leave the pilot, figuratively speaking, at the “pointy end of the spear.”

Our last line of defense is to recognize the things that pilots do wrong and to try to avoid repeating those mistakes.


Unsafe acts can be loosely categorized into either errors or violations on the part of the pilot. Wiegmann and Shappell’s human factors analysis classification system (HFACS) specifies three basic types of errors a pilot can make: decision errors, skill-based errors, and perceptual errors.

While the reason for a decision error is sometimes unclear, we can still classify unintentional bad decisions as errors as opposed to violations. For example, using the wrong procedure or maneuver during flight could be due to bad decision or lack of knowledge.

And if it is indeed a bad decision, this kind of error can be because of an ill-structured decision or failure of choice among several alternatives. Pilots can best ameliorate decision errors by following rules, procedures, and checklists carefully, as well as continually striving for a high level of aeronautical knowledge.

Skill-based errors are one of the most common types of errors that pilots commit. In fact, the NTSB has made statements in the past indicating that skill-based errors appear to be on the rise as we hand over control to automation in the cockpit. That’s a discussion for another day, but we pilots need to take special notice of our flying skills.

Among the skill-based errors recorded in the accident records, loss of control ranks high, as does loss of situational awareness due to distractions of various sorts. In many cases the pilot committing the skill-based error is “current” relative to regulatory requirement.

This is a good time to remind everyone that currency does not necessarily equate proficiency.

Although there is no set amount of practice that keeps all pilots proficient, we can all seek independent assessment of our skills from a qualified flight instructor. The problem with self-assessment is that a slow loss of skill over time may go unnoticed and the lower level of performance may become the standard by which you measure yourself.

Skill-based errors deal with more than just stick-and-rudder skills however. Attentional failures and memory lapses are part of this group as well. As mentioned earlier, loss of situational awareness due to distractions is frequently a result of the failure to prioritize tasks in the cockpit.

Upsetting the age-old “aviate, navigate, communicate” priority structure is a great way to shift attention away from the primary goal (flying the airplane) and wind up in an unusual attitude.

As for memory lapses, we all forget things time to time. For pilots, this type of error can mean leaving out a critical emergency procedure step, or leaving out a normal procedure step and creating our own emergency. In either case, the best solution to keep from falling prey to this trap is practice, practice, practice!

The more familiar a procedure is, the more likely your responses to a situation will be automatic and reliance on the checklist will be less.

One suggestion to help in this area is to review a different emergency procedure prior to each flight. This constant review will not only make you feel more comfortable during normal flight, but will greatly improve your chances of a quick and accurate response during an emergency.

But please be sure you are practicing correctly. Practicing skills incorrectly leads to incorrect action during critical flight events when responses are more automatic.

One last area of errors are those of the perceptual nature or simple misjudgment. There are certain illusions out there that we just can’t do much about. Take landing illusions due to differences in runway width, length, and/or slope.

We have no control over such things, but we are certainly perceptually confused by them.

This being the case, one would expect that there is little we can do about it, but the opposite is quite true. The simple awareness of what causes these various illusions forces the pilot to rely on other than solely visual cues to complete the flying task. So knowing when to expect a visual illusion is at least half the battle to preventing them from guiding you to disaster.

Similar to perceptual errors are errors of judgment. This isn’t the type of error such as making a decision to fly on a bad weather day (that’s a decision error), but rather a failure to judge physical properties during flight.

A great example is the pilot who misjudges the speed as a result of monitoring movement over the ground instead of the airspeed indicator. Another common example of misjudgment deals with obstacle clearance. The phrase, “I thought I had enough room to clear it,” is more common than you might imagine.

People are generally not as good at judging spatial relationships in dynamic environments and in particular where visual cues are sparse. I suppose if we were, we wouldn’t feel like we need all those fancy flight instruments.

In lieu of honest mistakes or errors, there are violations, both routine and exceptional, that lead to accidents. While a decision error could lead to a regulatory violation, the violations I’m referring to here are those with a certain intentionality to them.

Pilots inherently know (or are supposed to know) what’s right and wrong when it comes to following the rules and regulations. However, we don’t always follow the rules like we’re supposed to.

In cases where pilots regularly stray from the rules, such as failing to get a complete preflight weather briefing, flying through that little scattered cloud, etc. and are rarely if ever penalized for the act, we say that they have committed a routine violation. In a sense, the lack of penalty or enforcement from the regulatory body may indirectly condone that behavior.

On the other hand, isolated departures from the regulations are considered exceptional violations. This is where pilots make an exception for themselves to break the rule, knowing full-well that what they are doing is disallowed by regulation.

The difference between routine and exceptional violations is the sense that if it’s routine, it’s more of a habitual departure from the rules, and the exceptional is a one-time occurrence (often preceded by the phrase “watch this!”).

One type of violation is not necessarily more acceptable than the other, but one may simply be more common among pilots for a given flight scenario. With either type of violation, the simple solution is to not break the rules!

In the grand scheme of things, pilots can have several preconditions for unsafe acts stacked against them (as I talked about last month). In combination with an unsafe act of an error or violation, these preconditions can effectively eliminate any barrier preventing an accident.

A sequence of events or conditions usually leads to the accident scenario, and absent defenses invariably leaves the pilot at the pointy end of the spear!

This month’s Pilot Primer is written by Donald Anders Talleur, an Assistant Chief Flight Instructor at the University of Illinois, Institute of Aviation. He holds a joint appointment with the Professional Pilot Division and Human Factors Division. He has been flying since 1984 and in addition to flight instructing since 1990, has worked on numerous research contracts for the FAA, Air Force, Navy, NASA, and Army. He has authored or co-authored over 180 aviation related papers and articles and has an M.S. degree in Engineering Psychology, specializing in Aviation Human Factors.