USA TODAY International Edition
Balance on board and other weighty issues
Question: Some aircraft have three seats on one side of the aisle and two seats on the other side. Does this imbalance affect aircraft performance? Shouldn't the weight be distributed evenly on each side of the aircraft?
— submitted by reader Matthew R, Syracuse, N.Y.
Answer: The weight is balanced due to the aisle being offset a bit. Airplanes such as the DC-9, MD-80/90 and Boeing 717 have the 3-2 seating in the main cabin. They fly normally with no imbalance due to good design engineering.
Q: On Allegiant Air they try to get customers to pay for picking a particular seat. Recently, while traveling with my wife on tickets booked together they seated us in different rows. They then make an announcement saying that nobody should switch seats because they use a computerized weight and balance system on the plane. I can appreciate the fact that balance is important in aircraft performance but baggage seems to get loaded in a pretty random manner with little concern for weight and balance. Can you provide any clarification?
— Joe, Springfield, Ill.
A: Many airlines use computer weight and balance programs. The airplane is divided into zones and the number of passenger in each zone is entered in the program. This allows for the balance of the airplane to be determined. It is likely that your flight was near a limit and they did not want people changing zones.
Your statement about baggage being loaded randomly is not correct. The weight in each cargo compartment is calculated before loading. Airlines use standard weights for bags and people, allowing them to do the calculations in advance. This speeds up the loading process significantly.
Q: I was flying Akron Canton to Charlotte on United and right before we left the flight attendant needed someone to move to the back because of weight. How can 100-200 pounds make a difference and why?
— Lisa Crall, Bolivar, Ohio
A: In some airplanes, it can make a difference. Before every flight, performance calculations are done to ensure that the airplane can safely take off and land. One of the calculations is the weight of the airplane; another is the balance. Balance is important for proper control (primarily pitch control) during takeoff and in flight. During certification, the manufacturer demonstrates various balance points, known as center of gravity, to the regulator (in the U.S., that is the FAA). Based on those demonstrated points, a flight envelope is developed. To maintain the proper balance, the center of gravity must be within the envelope and the airplane is loaded with passengers, cargo and fuel accordingly. In your case, it was necessary to move one person aft to move the center of gravity back into the envelope.
Q: Why would passengers be removed unwillingly for an overweight aircraft? Aren't the paying passengers the first part of the weight and balance formula?
— Neil, East Aurora, N.Y.
A: The first part of the weight and balance plan is the fuel needed for the flight. Load planning agents then account for the scheduled passengers, bags and cargo. Variations to the planned load can result in overweight conditions. A decision has to be made how the weight can be reduced; sometimes it is removing a few passengers. Removing passengers can be faster than removing an equal amount of bags. This is a difficult decision for the ground staff to make.
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