NASA has added fuel to the burning issue, of airline pilot flight time limitations (FTLs), by claiming scientific evidence that maximum standard crew duty times, should be well below almost, all existing national limits. In doing so, it has probably wrong-footed Europe's Joint Aviation Authorities (JAA) on a highly emotive subject.

Regulators tend to see FTLs as providing a means for improving safety through imposing maxima: some pilots seem to regard FTLs as being a means for airlines to increasingly exploit them, by effectively imposing minima. By questioning the JAA's controversial proposals, NASA may well be seen to be taking sides against the regulators.

One of the more surprising aspects of this debate is that - if the US Federal Aviation Administration is influenced by the latest NASA proposals - the USA could be heading for far more restrictive regulations than is Europe. Surprising, at least, to those who look on the European Union and the "Social Chapter" of its constitution, as being obsessed with improving the lot of the employee at the expense of the employer, but perhaps not so surprising to those who look at the USA, as a hot bed of litigation.

If there is to be legislation it would be to the benefit of all if it could be on a common international basis. There are, of course, wildly differing conditions applying in Europe and North America. Many US domestic flights are both longer and pass through more time zones than do the bulk of European international flights. The stress-drivers in the two environments may be very different - but the one environment is not necessarily any more stressful than the other.

Given that, it is difficult to see how - if the basis for recommending FTLs is scientific investigation - the recommendations from the two sides of the Atlantic can be so different. When NASA's full report is published, with all its data sources and reasoning made clear, the airline operators, pilot associations and regulators will have a duty to look carefully at what it says, and not to dismiss it as the stuff of absent-minded scientists. It is the regulators who, in the end, have the responsibility for making the decisions - but they do have a duty to take into account years of actual line experience and others' investigative work.

There has always been something of a stand off between operations people and specialists in the various branches of aviation medicine, and nowhere is this more obvious than on the issue of FTLs. The effects of tiredness and fatigue are difficult to quantify, and it is well known that people can perform apparently well (or at least adequately) in complex tasks after appallingly long periods of work and stress.

Just how well those tasks are performed, however, remains open to question. Nobody denies that "pilot error" remains the most frequent primary or major factor in fatal and serious accidents. What is less well understood is what part fatigue or tiredness may have played.

Accident reports always state the amount of time that the crew have been on duty for the flight concerned, and usually report their time-on-duty for the complete shift if it has been a multi-sector day for them. It is rarely reported how many duty hours have been worked in the previous week, fortnight, month and year.

Fatigue, as aviation physicians and psychologists define it, is a state where tiredness has reached the stage of degrading the efficiency of the human machine, like disease does. Regulations about FTLs, where they exist - and, unbelievably, they do not exist in some countries - have sought to control the disease, but without necessarily identifying just what the disease is. NASA's study is claimed to be scientific: if it is, and it calls into question much of existing practice, then it could indeed justify a major shake-up.

Publication of NASA's report has come at an inconvenient time for the JAA regulators, who are struggling to bring together this year the whole European Union's operations regulations into a common set of rules. NASA's findings could alter the whole basis of those proposals.

Source: Flight International