Crash Raises Concerns About Weight, Stability In Commuter Flights
Posted January 16, 2003 1:38 a.m. EST
CHARLOTTE, N.C. — Flying too close to the known limits on a plane's weight and balance can have catastrophic consequences for commuter airplanes like the one that crashed last week in Charlotte, killing 21, aviation experts say.
As federal investigators focus on how heavy weight and improper balance may have combined with a mechanical failure to cause the Jan. 8 crash of US Airways Express Flight 5481, observers say those conditions could be recreated on any of thousands of commuter-plane flights that take off each day.
"I think it's one of the things that may make commuter flying riskier," said Jim Burnett, a former chairman of the National Transportation Safety Board, "especially when you're flying with a loaded airplance - the possibility that it could be out of weight or out of (its center of gravity) because of variations in the average passenger weight and the distribution of weight."
Federal investigators have said they are examining maintenance that was done Jan. 6 on the Beech 1900's elevator assembly - which controls the vertical movement of the plane's nose - as well as weight and balance issues in their probe of the crash.
Among the weight and balance concerns:
Air Midwest, the carrier that operated the flight, assumes that passengers flying in winter average 175 pounds each, including clothing and carry-ons. But given the super-sizing of American waistlines (adult men averaged 180.7 pounds in 1994, the most recent year in which statistics from the federal Centers for Disease Control are available) and the increased size and weight of carry-ons, that standard could have been exceeded on Flight 5481.
John Goglia, the NTSB member who headed the crash scene investigation, said a member of the ground crew believed the plane was limited to 26 bags. He said Capt. Katie Leslie determined that all 31 checked bags could remain on board.
According to Goglia, pilots and others interviewed in the investigation said they thought the plane "looked heavy" as it prepared for takeoff.
Goglia also has said the early stages of the NTSB's investigation indicated the 17,000-pound plane was 100 pounds below its maximum weight and within one percent of the rearward limit for its center of gravity.
Given those conditions, said Paul Czysz, a professor emeritus of aviation and engineering at St. Louis University, any miscalculation of the center of gravity or loading that pushed unanticipated weight toward the rear could have made the plane unbalanced.
Problems could have included too many bags in the rear baggage compartment or simply having several heavy-set men seated in the rear.
Czysz and others said that airplane weight limits generally have a built-in safety margin, much like the "empty" line on automobile gas tanks.
"You could be 10 percent over the weight limit of an airplane and still fly it," Czysz said.
The location of a plane's center of gravity is not as forgiving. The FAA said a pilot may not fly a plane if its center of gravity is beyond its forward or aft limit, because such a plane can be uncontrollable once airborne.
"It's a very black-and-white thing," Czysz said.
Mary Schiavo, a former inspector general for the Federal Transportation Department, said margins of error are thin in commuter planes like the 19-passenger Beech 1900.
"The small plane, being so light ... you don't have a lot of leeway," said Schiavo, now a Los Angeles-based lawyer who litigates air disaster cases.
A small-plane crash in the Bahamas that killed singer Aaliyah and eight others in 2001 was blamed in part on a plane that was overloaded by at least 700 pounds.
David Stempler, president of the Washington-based Air Travelers Association, a passenger-advocacy group, said he has heard for years from commuter pilots concerned about weight and balance issues. Last week's crash heightened worries, he said.
"I think what we need to do for planes under 30 seats is weigh all checked and carry-on bags that go into the cargo compartment," he said.
The industry likely would resist change. Air carriers already operate on extremely thin profit margins; telling them they must reduce the number of passengers or the amount of cargo they carry would only further harm a financially ailing industry.
Passengers already dealing with stepped-up security screenings are unlikely to put up with being weighed before boarding a plane, and studies have shown people do not accurately self-report their weight.
In-ground scales that weigh planes and measure their weight distribution as they head for the runway - double-checking the work of pilots and load managers who currently perform such calculations - are prohibitively expensive.