Safety - Emergency In Flight

Incapacitation of the pilot in command of an airliner is definitely alarming to the passengers, the regulatory authority and of course, the medical system that in the first place, cleared the pilot to fly

Although a rare occurrence, one does sometimes hear of a pilot of an airliner succumbing to a heart attack mid-air. Occasionally, the co-pilot takes over controls when the Captain of the aircraft was, for some reason, physically incapacitated and had to be taken out of the cockpit for emergency medical care. In fact, last November, when the co-pilot of a Boeing 747 on a transcontinental flight suffered a debilitating migraine attack, an off-duty pilot travelling as a passenger replaced the missing crew and the flight continued to its destination. While the demise of a pilot in flight is shocking, the consequences of mere incapacitation can be no less catastrophic.

Thanks to a fairly rigid and universal system of initial and periodic medical evaluation of aircrew, incidents of in-flight incapacitation are not too frequent and may not seem alarming. But incapacitation of the pilot in command of an airliner is definitely alarming to the passengers, the regulatory authority and of course, the medical system that in the first place, cleared the pilot to fly.

In-flight incapacitation is clearly a problem that lies in the domain of aviation-medicine as well as that of flight training, the former being concerned with prevention and the latter, with the management of its occurrence. One of the main objectives of aviation medicine has been to completely eliminate the possibility of such an episode while in flight. Similarly, evolution of cockpit design, Standard Operating Procedures, the concept of crew resource management (CRM) and air traffic control procedures and aircraft maintenance practices, involve agencies such as the original equipment manufacturers, the regulatory authority and the airlines. All these agencies are concerned along with the problem of incapacitation of the pilot in flight, apart from other contingencies.

Nature of Incapacitation

The International Civil Aviation Organization (ICAO)’s medical definition for incapacitation is: “any reduction in medical fitness to a degree or of a nature that is likely to jeopardise flight safety.” An operational definition would be: “any physiological or psychological state or situation that adversely affects performance.”

Incapacitation has been described as “sudden” and “subtle”. There is quite a variation in the degree of incapacitation, from “total” to “uncertain” and both these types can challenge the acknowledgement by the other healthy cockpit crew member. A particular category of incapacitation has been identified as “cognitive”. The problem created by such incapacitation is difficulty in dealing with a pilot who is disoriented or mentally incapacitated or is obstinate while being physically able and vocally responsive. These cognitive incapacitations may seem psychologically based, but in some cases, the underlying cause can be pathological as with brain tumours, metabolic or frank psychiatric disorders leading to erratic performance. Retrospectively, there often seems to have been ample warning of an impending problem. In most cases, the pilot may have demonstrated inappropriate behaviour involving action or inaction as well as failure to comprehend, perceive and pass judgement.

Incapacitation can take place in any phase of flight, though an occurrence during take-off or landing and can have devastating impact on flight safety. All cockpit crew training procedures, especially CRM training to handle such an occurrence, is intended to confirm its presence and then taking over of controls and duties by the healthy member. At altitudes above 20,000 feet, explosive or slow decompression, pressurisation failure, fire, toxic smoke and the presence of carbon monoxide can result in hypoxia that is the most sinister of incapacitating hazards. This is sinister because the symptoms of hypoxia can vary from “normal” behaviour initially at least, to outright loss of consciousness, all within a matter of seconds. The possibility of feeling a “high” can be most distractingly devious. Procedures related to donning of oxygen masks are of primary importance here. During the remedial descent processes, decompression sickness can take its toll, especially where there is a pre-existing illness.

Medical conditions that can cause serious incapacitation include uncontrolled diabetes mellitus, high blood pressure, unexpected side-effects of self medication, various forms of epilepsy, and cardiovascular diseases. This is not to suggest that members of the aircrew are declared fit to fly with incomplete medical evaluation or observations. But they do have a penchant to either disregard or seek medical advice outside the aviation medicine domain. It is worth mentioning a positive facet of medical disposals here. After recovering from cancer, a heart attack or cardiac surgery, medical clearances attempt to follow the “one per cent rule”. Here is a magnificent bit of statistical foreplay which aims to balance flight safety risks with financial considerations for the pilot and the operator. The rule accepts that if a hundred pilots with similar medical condition are flying, only one of them will suffer from recurrences/complications, necessitating further grounding.

Statistical Analysis

To quote the ICAO document, during the last decade of the 20th century, a number of contracting states were approaching a fatal accident rate of one in ten million flying hours. Some of these states, therefore, set as their target, for all cause maximum fatal accident rate, a figure of one in ten million flying hours with human failure risk constituting one tenth of the risk and human failure caused by medical incapacitation comprising one-tenth of the human failure risk, or onehundredth of the total risk. The rationale gets even more complex but results in the acceptance of a medical-cause-accident-rate of no more than one in ten billion flight hours. Given the well-worn cliché that medicine is not an exact science, this is the best possible compromise, though some states even advocate the “two per cent rule”. The important point here is that states should work towards defining objective fitness criteria to encourage consistency in decision-making.

According to a study carried out in 1991 by ICAO, gastrointestinal conditions constitute about 75 per cent of self-limiting incapacitations. Uncontrollable bowel action constituted 21 per cent of these, with colicky pain, nausea and vomiting causing the remaining.

While these may represent a little more than varying degrees of discomfort and inconvenience, they can also be completely incapacitating. Fortunately, time for a planned handover is possible in most instances. Herein lies a lesson. Airlines attempt to provide cockpit crew with food from different sources. Fair enough. But what about the lack of discipline when a crew member has a meal prior to flight from an unhygienic restaurant or consumes foods he/she is known to be allergic to? Other potentially incapacitating conditions include earache (eight per cent), fainting/weakness (seven per cent), headaches/migraines (six per cent) and vertigo/disorientation or the lack of situational awareness (four per cent). There is no reference to fatigue-induced “sleep attacks”, drowsiness due to medication or epileptic conditions in this report and there is plenty of reason to accept that the incidence of these conditions are higher than what one would like to believe.