There is an interesting analogy to non-standard wiring of flight control sticks in the field of anaesthesiology. It makes interesting reading and I quote from it below. Maybe someone in the aviation world can calculate the incremental reduction in risk that common design aspects across a family of aircraft could generate.
In the book ‘The best American Science writing 2000’, Atul Gawande writes about the incidence of fatalities resulting from general anaesthesia. In the US, between 1960 and 1980, this averaged at 1 in 10,000 operations. Acceptable risk? Maybe not if you weigh the ratio against total operations annually. In 1982, this equated to 6000 patient killed or brain damaged. Fortunately, the incidence is greatly reduced today, thanks to an engineer named Jeffrey Cooper. To quote from the book,
“An unassuming, fastidious man, Cooper had been hired in 1972, when he was twenty-six years old, by the Massachusetts General Hospital bioengineering unit, to work on developing machines for anesthesiology researchers. He gravitated toward the operating room, however, and spent hours there observing the anesthesiologists, and one of the first things he noticed was how poorly the anesthesia machines were designed. For example, a clockwise turn of a dial decreased the concentration of potent anesthetics in about half the machines but increased the concentration in the other half. He decided to borrow a technique called "critical incident analysis"--which had been used since the nineteen-fifties to analyze mishaps in aviation--in an effort to learn how equipment might be contributing to errors in anesthesia. The technique is built around carefully conducted interviews, designed to capture as much detail as possible about dangerous incidents: how specific accidents evolved and what factors contributed to them. This information is then used to look for patterns among different cases.
Getting open, honest reporting is crucial. The Federal Aviation Administration has a formalized system for analyzing and reporting dangerous aviation incidents, and its enormous success in improving airline safety rests on two cornerstones. Pilots who report an incident within ten days have automatic immunity from punishment, and the reports go to a neutral, outside agency, NASA, which has no interest in using the information against individual pilots. For Jeffrey Cooper, it was probably an advantage that he was an engineer, and not a physician, so that anesthesiologists regarded him as a discreet, unthreatening interviewer.
The result was the first in-depth, scientific look at errors in medicine. His detailed analysis of three hundred and fifty-nine errors provided a view of the profession unlike anything that had been seen before. Contrary to the prevailing assumption that the start of anesthesia ("takeoff") was the most dangerous part, anesthesiologists learned that incidents tended to occur in the middle of anesthesia, when vigilance waned. The most common kind of incident involved errors in maintaining the patient's breathing, and these were usually the result of an undetected disconnection or misconnection of the breathing tubing, mistakes in managing the airway, or mistakes in using the anesthesia machine. Just as important, Cooper enumerated a list of contributory factors, including inadequate experience, inadequate familiarity with equipment, poor communication among team members, haste, inattention, and fatigue.
The study provoked widespread debate among anesthesiologists, but there was no concerted effort to solve the problems until Jeep Pierce came along. Through the anesthesiology society at first, and then through a foundation that he started, Pierce directed funding into research on how to reduce the problems Cooper had identified, sponsored an international conference to gather ideas from around the world, and brought anesthesia-machine designers into safety discussions.
It all worked. Hours for anesthesiology residents were shortened. Manufacturers began redesigning their machines with fallible human beings in mind. Dials were standardized to turn in a uniform direction; locks were put in to prevent accidental administration of more than one anesthetic gas; controis were changed so that oxygen delivery could not be turned down to zero.”
……”Today, anesthesia deaths from misconnecting the breathing system or intubating the esophagus rather than the trachea are virtually unknown. In a decade, the over-all death rate dropped to just one in more than two hundred thousand cases--less than a twentieth of what it had been.
Reference
Gawande, A., “When doctors make mistakes”, In “The best American science writing 2000”, Ed. James Gleick, ECCO Harper-Collins, New York 2000.