AMERICAN VS. SWISS CHEESE - Refocusing on pilot error, the real threat

  • Published
  • By Retired Lt. Col. Edward H. Linch III
  • Chief of Flight Safety
American cheese versus Swiss cheese can send your taste buds into a mouth-watering dilemma when it comes to hamburgers and hoagies. It turns out these sandwich complements also can spark debate in flying safety circles when it comes to the study of human factors in aviation mishaps.

In the pursuit of understanding pilots and aircraft accidents, the study of human factors in aviation has evolved with many philosophies, theories and causation models dominating our safety culture. Dr. James Reason's "Swiss Cheese Model," the most popular causation model used throughout the health care and aviation industry, including within the Department of Defense, equates human systems to multiple slices of Swiss cheese. Organizational influences, unsafe supervision, preconditions for unsafe acts and unsafe acts (errors and violations) are all slices of cheese in his model. If the holes (weaknesses, hazards, failed or absent defenses) in each slice 
of cheese line up with each other, then a mishap will occur.

The "Swiss Cheese Model" is deeply intertwined in our mishap investigation process as the foundational model for the Human Factor Analysis and Classification System. However, one constant remains; the majority of flight mishaps are not caused by the system, but by pilots making mistakes. These types of mishaps could have been prevented by having a clearer focus on basic airmanship: skill, proficiency, discipline, and judgment and decision-making.

After studying mishaps in the Air Force for years, however, I've noticed a trend that can't be overlooked.

It's the last slice of cheese in Reason's model: unsafe acts, which are the pilot's errors and violations.

Skill-based errors are the root cause of many mishaps. Examples of these types of mistakes can include stick and rudder errors, inadvertent operations, as well as checklist, procedural and maneuvering errors.

Additionally, errors in judgment and decision-making can cause problems. These mistakes can include risk assessment, task misprioritization, ignored warnings, rushed operations, problem solving, weather avoidance, failure to go-around or aborting a takeoff, to name a few.

Other hazards are perceptional errors -- improper response to spatial disorientation, visual illusions, etc.

And, finally, there are outright violations, which highlight the pilot's attitude and lack of discipline in the cockpit. These involve deliberately breaking training rules and regulations.

We're our own worst enemy regarding errors and violations.

Not to discount Dr. Reason, I've got a new causation "cheese" model to consider in the study of human factors: "The American Cheese Pilot Error Model." It's about personal responsibility and choices.

"The American Cheese Pilot Error Model" is a single slice 
of cheese that totally focuses on the pilot, versus the system. Yes, the organization and supervision can influence the pilot. Yes, preconditions (physical and mental limitations, fatigue, personal readiness. etc.) can set aviators up for a bad day. But, 
it all boils down to the last slice of cheese, which is the pilot 
and the choices he or she makes.

The pilot-in-command is the one ultimately responsible for preventing errors during all aspects of the flight, from flight planning to debriefing. No one has ever been forced to fly by the organization or supervisor, and the pilot is the one who chooses to fly with excessive preconditions. He's the one who signs for the aircraft. He's the one who chooses to push the envelope and fly when he's too fatigued, distracted, or having personal, supervisory or organizational issues, for example.

He's the one who can call knock-it-off.

It's all about the pilot!

The pilot is the one who has to figure out how to fit into the organization and meet the needs of his supervisor by managing his personal life and staying proficient at flying the aircraft without negatively impacting him, his crew or his aircraft.

Human factors, in my opinion, can be defined as anything affecting your life that you can control, change, transfer or eliminate to bring about a different outcome by planning and anticipating as you respond in a fluid environment. It involves staying ahead of the aircraft by preparing for the "worst case" and anticipating the next event in the chain. ... Actually, this concept can be applied to all aspects of life.

Channelized attention, misprioritization, task saturation, failure to communicate, loss of situational awareness, and improper, late or no reaction to change, for example, are common preconditions that can be controlled, changed, transferred or eliminated by a pilot's actions. To do this, he's got to know his aircraft like the back of his hand, which means proficiency not only in the aircraft but with emergency procedures in the simulator, too. Pilots need to know their flight/crewmembers and their capabilities; know their own limitations and don't exceed them; and fly simple, realistic and focused tactics to complete the mission versus over-tasking with complex plans with little margin for error or room for contingencies. Aviators need to be prepared to quickly respond to changes in a fluid environment, formulate a plan, stick with it, and not let external pressures force them into a corner. They need to keep the focus and not let their guard down. They can relax once they're in the chocks.

The Swiss Cheese Model is a great tool to analyze the overall safety system and dissect a mishap; however, it doesn't address the root cause and how to proactively combat it.

"The American Cheese Pilot Error Model" encourages 
pilots to focus on keeping skills and proficiency high, making sound decisions with conservative judgment, and maintaining strict discipline. Remember, combating human error is tough. 
I challenge pilots to take a look at themselves the next time they fly and see if they have the proper focus to fly and successfully complete the mission safely.

Let the debate between American and Swiss continue. But, remember, sometimes no matter how you slice it, these two cheeses work best when "consumed" together.

Before his retirement, Lt. Col."Ned" Linch was the chief of flight safety for 12th Air Force at Davis-Monthan Air Force Base, Ariz. He is a command pilot with more than 26 years of flying experience in the Air Force (F-16s and F-111s) and airlines (727s and MD-88s).