Information Processing, Human Error and the Learning Process — Page 164, Lesson 261

I want to walk you through a core topic in aviation human performance: response times and human reliability. Let's start with the basics. Response time — or reaction time — is the time interval between the moment a signal appears and the moment you produce a response to that signal. In the simplest case, like pushing a button when a light comes on, that reaction time is about 0.2 seconds. That's a baseline. Now, if I complicate the task — say, two lights and two buttons — the reaction time increases. Why? Because the extra choice adds loading on the central decision maker. That's the part of your brain that has to process the information and decide what to do. More options, more load, more time. In aviation, reaction times are even longer because the decision element of the task is usually far more complex than pushing a button. Let me give you two real incidents that show this clearly. At Manchester, a bang was heard before V1 — that's decision speed, the speed beyond which you're committed to take off. The brakes were applied within one second. Why so fast? Because hours of simulator training have drilled in that for any emergency before V1, you stop the aircraft and deal with the problem on the ground. It becomes a reflex action. Now contrast that with Sumburgh airport, where an aircraft ran off the end of the runway. There, it took five seconds after the perceived emergency before the brakes were applied. Why the difference? At Sumburgh, the emergency occurred after V1. Training stresses that for any emergency after V1, you continue the take-off run and handle the problem in the air. But in this case, the emergency was that the aircraft could not get airborne — the elevator locks had become engaged. The central decision maker had to take time to override the ingrained desire to get the aircraft off the ground. That override took several seconds. So here's the key principle: It is of paramount importance to make the correct response rather than a fast response. Speed is useless if the action is wrong. Now let's move to human reliability. The ancient saying goes: "It is in the nature of man to err" — Cicero. That's our starting point. Human reliability is defined as an individual functioning in the manner in which he or she is supposed to function. Studies show that during a simple, repetitive task, errors occur about once in 100 times. That error rate — 1 in 100 — is built into the human system. And it can increase rapidly when stress, fatigue, or low morale are added factors. The good news: with practice, human reliability can be improved by several orders of magnitude. Frank Hawkins is quoted as saying that an error rate of 1 in 1,000 might be thought of as "pretty good" in most circumstances. Now, what factors affect human reliability? Here's the list: - Length of time of exposure to risk — the longer you're exposed, the more likely an error. - Degree of risk — how serious the consequences are. - Mental and physical health — your overall condition. - Innate psychological characteristics — your built-in mental traits. - Innate physiological characteristics — your built-in physical traits. - Personality deficiencies — aspects of personality that may predispose you to error. - Stress factors — any source of stress. These are the factors that can push that built-in error rate higher or, with training and good conditions, bring it down. In aviation, understanding these is critical because we're not just pushing buttons — we're making complex decisions under time pressure, often with high stakes.