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Safety in Avionics: Air Safety and the Coefficient of Fiction

By David Evans | July 1, 2000
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The "coefficient of fiction" is a highly useful means of illustrating the relationship between avionics and safety. The term was presented in author John Gall’s trenchant 1975 book, Systemantics, subtitled, "How Systems Work and Especially How They Fail." The dust cover illustration shows the supposedly unsinkable Titanic slipping beneath the waves, providing a pointed illustration of performance versus promises. Despite the maritime metaphor, the 110 pages between the covers of this witty 25-year-old opus contain wisdom directly applicable to the safety of the airline industry.

To author Gall, no system is better than its sensory organs. Or, more precisely, the best systems are the ones that provide a clear view of reality to top management. Gall declared that the crucial variable is found in the fraction:

Cf= Ro/Rt

The numerator and denominator define the coefficient of fiction (Cf), where Ro is the amount of reality failing to reach relevant officials, and Rt is the total amount of reality presented to the system. Hence, Cf can range from zero (full awareness of outside reality) to unity (no reality is getting through). The closer the coefficient of fiction is to unity, the more likely managers are operating in fantasy land.

The coefficient of fiction bears directly on air safety. Those airlines that have put in place aggressive programs to analyze information captured in-flight appear to have achieved a better safety record than carriers without such programs. It could well result from a coefficient of fiction leaning more toward zero, a detailed look at reality.

Chris Hart, the Federal Aviation Administration’s (FAA’s) top gun for system safety, pointed out in a recent presentation that carriers who systematically analyze information recorded in flight "have an accident rate that’s about six times lower" than those operators who don’t have such programs. These activities are known generically as flight operations quality assurance (FOQA) programs. In the FOQA concept, data is recorded for every flight, not only to establish norms but also to pick out "exceedances."

The power of modern avionics, it seems, can be marshaled to improve safety. Hart uses a "global view" graph to make his point (see graph below). His information captures the turbine-powered aircraft accident rate over three periods, each spanning seven years: 1976-1982, 1983-1989, and from 1990-1996. The solid black line shows, worldwide, that the accident rate has indeed declined. The solid red line shows that the U.S. record consistently has been lower than the global average. That’s the comforting part.

The discomfiture stems from the picture this chart also shows–the U.S. does not enjoy the world’s best safety record. That claim goes to those carriers with FOQA programs in place. The comparison is an embarrassing illustration of a U.S. airline industry that is not taking the lead on a technology that may well be advancing safety. During the time period shown, no U.S. carrier had a FOQA program. Only since 1996 have U.S. carriers jumped on the FOQA bandwagon, as it were.

Three dotted green lines show accident rates for carriers with FOQA programs. The topmost dotted green line shows the accident rate for those carriers exploiting flight data recorder (FDR) information after every flight for less than seven years. The middle dotted green line shows those foreign carriers with FOQA programs for seven to 14 years, and the bottom dotted green line shows the record of carriers with FOQA programs in use for more than 14 years.

This last and lowest green line is the stunner. It shows an accident rate not only one-sixth the world average for the 1990-1996 time period, it reveals that carriers with FOQA programs had half the accident rate of U.S. carriers. So much for the oft-repeated claim that the United States has the best aviation safety record in the world.

Capt. Ed Soliday, head of safety at United Airlines, said the FOQA program put in place at his carrier is designed to surface lurking hazards. A confidential safety reporting system helps, too, in many instances by complementing the FOQA data. Soliday is less interested in searching through data for purposes of punishing crews. He simply wants to mitigate hazards. "I’d rather fix a systemic problem and save 100 lives than have a pound of flesh," Soliday declared.

At United, FOQA has produced data for analysis that clearly has benefited safety, as far as Soliday is concerned. He offered two examples:

  • Flap/slat exceedances. Defined as deployment of these high lift devices above desired airspeeds, Soliday said FOQA identified an exceedance rate of 3.4 per 100 flights–since brought down to 0.3 per 100 flights. This drop marks an order of magnitude improvement.

  • Dual control inputs. On the carrier’s new fly-by-wire A320s, dual control inputs occured at the rate of 1.44 per 100 flights. In a dual control input on the computerized A320, Soliday explained, "You only get half of what you think," due to the summing logic in the computer. In three months, the 1.44 rate was reduced by two-thirds to 0.4 dual control inputs per 100 flights.

There are hazards FOQA technology won’t pick up. An airplane could be descending on approach with no "exceedances," but if the crew has dropped below the glideslope, a collision with terrain could still result.

FAA’s Hart also cautions against inferring a direct cause-and-effect relationship between FOQA and safety. Other factors may exist. FOQA-equipped airplanes may be newer. FOQA-equipped airplanes may also be spending more time in radar controlled airspace and executing fewer non-precision approaches. And, last but certainly not least, airlines with better safety cultures may have been predisposed to invest in FOQA technology, which is why certain carriers were "early adopters," so to speak.

Even with these caveats, the British Airways rationale for its pioneering FOQA program seems unassailable. Capt. Roger Whitefield, the carrier’s head of safety, described the challenge thusly:

Knowledge is power.

You can’t put right what you don’t know is wrong.

The more you know, the better able you are to validate the effects of change.

It’s not even remotely possible to achieve this operational ethic in an organization where the paucity of data drives the coefficient of fiction close to unity (no reality percolates to the top). A coefficient of fiction approaching zero, however, is one where almost all possible safety related data gets through for action by relevant officials. The absence of accidents no longer suffices to prove the absence of hazards.

The relationship between information and safety is suggestive but tantalizing nonetheless: the more the coefficient of fiction can be driven to zero, the more likely the operator will have an accident rate approaching the same happy number.

David Evans is editor of the award-winning newsletter Air Safety Week. Comments can be directed to [email protected]

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