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"Takeoff depends on plane weight"



Wednesday, August 29, 2001

Takeoff depends on plane weight
Overloaded aircraft may need some passengers to disembark
By Bill Sones and Rich Sones Ph.D.
The Deseret (UT) News


      Question: During bad weather at a Colorado Springs airport, many
canceled flights forced switches of passengers, and finally one pilot
announced the plane was overloaded and couldn't take off. First fuel would
be removed, he said, then passengers if necessary. Overweight ones first?
How is a fully loaded jet airliner weighed, anyway?

      Answer: Modern transport planes have weight sensors, but the pilot is
ultimately responsible, says University of California-Davis professor of
mechanical and aeronautical engineering C.P. "Case" van Dam.

      Takeoff weight = the plane's empty weight + crew weight + oil + fuel +
payload. Typically, a passenger is assumed to be 150 lb. + 50 lb. of
luggage. Fuel weight is tracked during fueling or via indicator. Weight of
the plane empty is provided by the manufacturer and updated when equipment
is changed.

      Maximum allowable takeoff weight depends on atmosphere density and
runway length. Especially for high altitude operation such as at Colorado
Springs the pilot may conclude that not all seats can be filled.

      Then the airline figures out removal protocol, offering incentives to
volunteers. Mistakes do occur, and in a famous incident an Air Canada Boeing
767 ran out of fuel due in part to a volume miscalculation.

      Still 100 miles from Winnipeg and at 26,000 feet, the plane, said
"Soaring Magazine," had become in essence "a 132-ton glider with a sink rate
of 2,000-plus feet per minute."

      So Winnipeg was out, but an old military runway at Gimli seemed within
reach. Nearing touchdown came the shocking realization the runway was now an
auto racetrack! Moments later, pilot Bob Pearson stood on the brakes - tires
blew and the nose gear collapsed. The "Gimli Glider" came to rest barely a
hundred feet short of spectators, and with no critical injuries to
passengers.

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