Monday, August 28, 2006

Although the crash of Comair commuter flight 5191 at in Lexington, Kentucky, on Sunday appears to be the result of pilot confusion in choosing the wrong runway, it reopens debate on what steps the FAA should take in regulating a transportation industry that is struggling to serve an increasingly obese clientele safely with weight-sensitive commuter aircraft.

"We will be looking into performance data, we will be looking at the weight of the [Comair] aircraft, we will be looking at speeds," said Debbie Hersmann of the National Transportation Safety Board, according to an August 27 report from the Associated Press.

In January 2003 an Air Midwest Beech 1900 with 19 passengers aboard failed to gain altitude quickly enough and crashed into an airport hanger during takeoff in Charlotte, North Carolina. All passengers and crew died in the incident. The National Transportation Safety Board determined that Air Midwest used "substantially inaccurate weight and balance calculations for company airplanes," which were based on incorrect "average passenger and baggage weights." The NTSB recommended "periodic sampling of passenger and baggage weights [to] determine whether air carrier average weight programs [are] accurately representing passenger and baggage loads."

In August of last year, partly in response to the Charlotte incident, the Federal Aviation Administration released a 79-page advisory to airlines filled with tables and equations on how to ensure that the weight and the position of the center of gravity of aircraft are within safe limits.

Passengers contribute to an aircraft's weight not only with their bodies, but also with the fuel that is needed to carry the weight of their bodies.

The FAA gives airlines many options in how to ensure safe weight and balance, including actually weighing each passenger. However, in order to avoid offending their customers, few companies actually do this.

Some airlines ask each passenger his or her weight. If passenger-supplied weights are relied on, the FAA rules require that the weights must be increased by 10 pounds per passenger to correct for understated weight (see Note 1).

But most airlines just use a rule-of-thumb approved by the FAA based on the number of passengers and the male-female ratio. For "average" groups of passengers (which exclude athletic teams and military personnel), the standard rule of thumb was set in last year's advisory at 184 pounds for men and 163 pounds for women, up from 175 pounds for men and 135 pounds for women, a 9-pound increase for men and an 18-pound increase for women. In addition, the rule-of-thumb requires an additional 16 pounds to be added per passenger for carry-on items.

CalorieLab president Mark Schrimsher observed, "The growth in obesity may be outpacing the ability of FAA regulators to keep current. From a passenger safety standpoint, perhaps it is time for the FAA to require scales on the tarmac for commuter flights."

CalorieLab, Inc., operates a diet and weight loss resource and information web site at calorielab.com, with a nutrition and obesity news blog at calorielab.com/news.

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Note 1) A team from the Harvard School of Public Health reported in a recent study that people underreport their weight (and exaggerate their height) in public health surveys. In the case of women, the team reported an average 9-pound difference between reported and actual weight in the National Health and Nutritional Examination Survey, where participants know there will be an in person examination at a later date. In surveys where no in-person followup is done, such as the Behavioral Risk Factor Surveillance System of the Centers for Disease Control and Prevention, the discrepancies are thought to be even greater.

Note 2) The variable weight of a commuter aircraft comprises the weight of the fuel, the baggage weight, and the passengers' body weights. The minimum recommended runway length for an aircraft varies according its load, and includes a margin of safety. The CJR jet involved in the Lexington crash generally requires a 5,000- to 6,000-foot runway; the runway used on Sunday was only 3,500 feet long.

Note 3) In October of last year the Ethan Allen, a tour boat operating in the Adirondack Mountains, capsized, killing 20 of the 48 people aboard. An investigation by the NTSB concluded that the instability of the boat was partly due to "the use of an out-of-date average weight standard for passengers on public vessels."