Pilot flight time limitations have always been a hotly disputed subject, partly because of a lack of scientific research into fatigue

Flight time limitations (FTL) are all about preventing flightcrew fatigue and the associated dangers. At first sight, legislation to prevent pilot fatigue would be easy to write. But it never has been, and today it remains an issue of contention between the airlines, the pilots and the legislators.

The USA operates with a set of rules that all three parties are either directly unhappy with or uneasy about. Europe has been struggling for nearly 10 years to come up with a pan-European set of standards, but to anyone who thinks the system looks as if it is close to the finishing line, the advice is: Don't hold your breath. After its first reading in the European Parliament, the rules are now up for scrutiny by the Council of Ministers, which consistently sees FTL as a low-priority item and bypasses it.

The complications in setting FTLs arise because of the huge number of variables. It is not a question only of the maximum number of duty hours, but includes the number of sectors flown; the time of day or night the duty starts; the number of time zones to be crossed; the time of day or night the crew has to try to get some sleep; the minimum time between going off duty and reporting for the next duty, taking into account getting to and from a place of rest, eating, sleeping, eating again and returning to work; the maximum number of duty hours for the day/week/month and year; and whether these are worked out on a calendar basis or a 24h rolling basis. Finally, there is the number of hours the duty may be extended in exceptional circumstances, plus a definition of what circumstances qualify and how often this may be done in a given period. With potential complexity like that, it is easy to see why the UK Civil Aviation Authority many years ago said it is essential that any FTL rules "are observed in the spirit as well as the letter of the law", because any rule that attempted to cover all eventualities with no room for any flexibility would be unworkable as an efficient, as well as a safe, basis on which to roster crews.

Although it is common sense that fatigue reduces physical and mental performance standards, defining when fatigue becomes an unacceptable risk is the difficult part. FTL rules, as one expert pointed out, are not there to prevent pilots from being tired at the end of an honest day's work, but to protect passengers from pilots being deeply fatigued at the final landing in a long or onerous duty or succession of duty periods. It was only about 10 years ago that accident investigators seem to have started to consider that fatigue could be recorded as a "probable cause", or a causal factor. This is probably because it cannot be proven rather than because it was never there. But there have now been four major accident reports in which pilot fatigue has been recorded as a primary causal factor or contributory factor. An American International Airways McDonnell Douglas DC-8-61 freighter crashed on a good weather daylight approach to Guantanamo Bay, Cuba, on 18 August 1993; an Air Alg‚rie Boeing 737-200F crashed in December 1994 on a surveillance radar approach to Coventry Airport, UK, in poor visibility; an American Airlines Boeing MD-82 crashed on landing at Little Rock Airport, Arkansas, USA, in bad weather in June 1999; and more recently a Korean Air Boeing 747-300 on a non-precision night approach to Adana Airport, Guam, hit a hill, killing 228 people on board.

The main factor that has allowed so much argument to rage for so long is that almost all the studies carried out on the subject of fatigue have provided data that is disputable by one party or the other. If the airlines are happy, the pilots are not, and vice versa. Usually it is the airlines that dispute the data and pilots that quote it.

So it is good to see a promising new study being carried out in Australia. Taking part are an airline, its crews and a guiding academic institution that has expertise in this area. What is more, the study is going to be carried out in real time, on real duties as well as in flight simulators, and it looks as if this time the sample will be large enough to provide credible benchmarks against which safe and efficient rostering systems could worked out.

There will be those who will be motivated to dispute the findings, of course, but it is to be hoped the data derived from such extensive monitoring will add considerably to human understanding of a problem that is difficult to measure and impossible to prove in retrospect. This subject cannot be dismissed easily, even though the rules setting the limits will continue to be disputed, because people have died as a result of pilot fatigue, and that is official.

Source: Flight International