Private Pilot Flight Training and Instruction Flight Training Article Library | Back To 4VFR.COM Sleep The most common cause of diminished alertness and proficiency is lack of sleep. This condition is said to affect 30% of the U.S. population. This may be due to an actual loss of sleep or a change in a sleep pattern called the circadian rhythm. Pilots tend to neglect their need for sleep. The need for sleep is a defining limit to pilot mental capability. You must have sleep or your mind will fail. Once beyond the limit pilot performance deteriorates and can become irrational. Sleep is a restorative and can be both stored and deprived within limits set by the biological clock of the individual. As you grow older you will need less sleep. Jet lag sleep patterns are worse when flying from west to east. Accident rates climb precipitously when your body begins demanding sleep. The average American gets about one hour too little sleep each night. Accident rates rise in the afternoon and become significant at night. Postponing sleep causes a sleep deficit that as it increases an accident becomes more likely. Jet lag is a type of sleep deficit. A sleep deficit can best be resolved by going to bed early, not by sleeping late. A large deficit cannot be made up in one night. 21% of aircraft accidents cite sleep deficiency as a factor. When drowsiness occurs you cease to monitor the instruments. You will tend to fixate and drift off mentally. We go into a mental autopilot not thinking of what we are doing. This is the lowest level of alertness. The next level of alertness is one in which you are in constant search-and-scan, seeing what you are looking at, hearing what is said and asking question. This is the flying" mode from pre-flight to shutdown. This gradual deterioration of alertness is best observed in watching others. It can creep up on you and influence your flying without your even noticing. Your alertness rises again when you have located a problem. You focus on it and prepare to execute a solution. This might occur when required to make a crosswind landing. The highest level of alertness is when adrenaline begins to flow and survival becomes a factor. Written by Gene Whitt Flight Training Article Library | Back To 4VFR.COM